This glossary is intended as introductory material for novices (for more specific and technical detail, see the article corresponding to each term). It has been designed as a companion to Glossary of genetics and evolutionary biology, which contains many overlapping and related terms; other related glossaries include Glossary of virology and Glossary of chemistry.
One of two ends of a single linear strand of Шаблон:Gli or Шаблон:Gli, specifically the end at which the chain of Шаблон:Gli terminates at the third carbon atom in the furanose ring of Шаблон:Gli or Шаблон:Gli (i.e. the terminus at which the 3' carbon is not attached to another nucleotide via a Шаблон:Gli; Шаблон:Gli, the 3' carbon is often still bonded to a hydroxyl group). By convention, sequences and structures positioned nearer to the 3'-end relative to others are referred to as Шаблон:Gli. Contrast Шаблон:Gli.
A Шаблон:Gli ring with the carbon atoms numbered 1' through 5' according to chemical convention. The Шаблон:Gli is said to be upstream; the Шаблон:Gli is said to be downstream. Bonds to a generic Шаблон:Gli and a phosphate group are also shown.
A specially altered Шаблон:Gli attached to the Шаблон:Gli of some Шаблон:Gli as part of the set of Шаблон:Gli which convert raw transcripts into mature RNA products. The precise structure of the 5' cap varies widely by organism; in eukaryotes, the most basic cap consists of a Шаблон:GliШаблон:GliШаблон:Gli bonded to the triphosphate group that terminates the 5'-end of an RNA sequence. Among other functions, capping helps to regulate the export of mature RNAs from the Шаблон:Gli, prevent their degradation by Шаблон:Gli, and promote Шаблон:Gli in the cytoplasm. Mature Шаблон:Gli can also be decapped.
One of two ends of a single linear strand of Шаблон:Gli or Шаблон:Gli, specifically the end at which the chain of Шаблон:Gli terminates at the fifth carbon atom in the furanose ring of Шаблон:Gli or Шаблон:Gli (i.e. the terminus at which the 5' carbon is not attached to another nucleotide via a Шаблон:Gli; Шаблон:Gli, the 5' carbon is often still bonded to a Шаблон:Gli group). By convention, sequences and structures positioned nearer to the 5'-end relative to others are referred to as Шаблон:Gli. Contrast Шаблон:Gli.
The region of an Шаблон:Gli to which one or more Шаблон:Gli bind, causing the substrate or another molecule to undergo a chemical reaction. This region usually consists of one or more Шаблон:Gli residues (commonly three or four) which, when the enzyme is Шаблон:Gli properly, are able to form temporary chemical bonds with the atoms of the substrate molecule; it may also include one or more additional residues which, by interacting with the substrate, are able to catalyze a specific reaction involving the substrate. Though the active site constitutes only a small fraction of all the residues comprising the enzyme, its specificity for particular substrates and reactions is responsible for the enzyme's biological function.
The covalent attachment of any acyl group (e.g. acetyl or benzoyl) to a chemical compound, protein, or other biomolecule via the substitution of the acyl group for a hydrogen atom, either spontaneously or by enzymatic catalysis.[3]Шаблон:Gli is a type of acylation.
A Шаблон:Gli diphosphate consisting of Шаблон:Gli attached to two consecutive Шаблон:Gli groups via high-energy ester bonds. ADP can be Шаблон:Gli to produce Шаблон:Gli and thus is a precursor for its synthesis; it can also be dephosphorylated into Шаблон:Gli.
A Шаблон:Gli consisting of Шаблон:Gli attached to a single Шаблон:Gli group via a high-energy ester bond. Additional phosphate groups can be added to AMP to produce Шаблон:Gli and Шаблон:Gli; the Шаблон:Gli serves as a second messenger in some signaling pathways.
A Шаблон:Gli consisting of Шаблон:Gli attached to three consecutive Шаблон:Gli groups via high-energy ester bonds. The conversion of ATP into Шаблон:Gli or Шаблон:Gli via hydrolysis of these phosphates releases energy which is used to drive the majority of energy-consuming chemical reactions in all living cells, and hence ATP functions as a universal and ubiquitous energy carrier which is often referred to as the "molecular currency" of intracellular Шаблон:Gli. It is continously regenerated via Шаблон:Gli of ADP and AMP by enzymes such as ATP synthase. Like other nucleoside triphosphates, it also serves as a precursor for Шаблон:Gli synthesis.
Шаблон:Gli (ATP) is continuously decomposed into Шаблон:Gli (ADP) and regenerated by the loss and gain, respectively, of one or more phosphate groups.
One of three main biologically active Шаблон:Gli of the Шаблон:GliШаблон:Gli, along with Шаблон:Gli and Шаблон:Gli. The A-form helix has a right-handed twist with 11 Шаблон:Gli per full turn, only slightly more compact than B-DNA, but its bases are sharply tilted with respect to the helical axis. It is often favored in dehydrated conditions and within sequences of consecutive Шаблон:Gli nucleotides (e.g. Шаблон:Font); it is also the primary conformation adopted by Шаблон:Gli and Шаблон:Gli.[5]
Any pair of organisms which are related genetically and both affected by the same Шаблон:Gli. For example, two cousins who both have blue eyes are an affected relative pair since they are both affected by the Шаблон:Gli that codes for blue eyes.
A laboratory method used in molecular biology to extract and isolate Шаблон:Gli such as the DNA of Шаблон:Gli (as opposed to Шаблон:Gli) from certain cell types, commonly Шаблон:Gli bacterial cells.
One of multiple alternative versions of an individual Шаблон:Gli, each of which is a viable Шаблон:Gli sequence occupying a given position, or Шаблон:Gli, on a Шаблон:Gli. For example, in humans, one allele of the eye-color gene produces blue eyes and another allele of the same gene produces brown eyes.
Any Шаблон:Gli that differs from an ordinary Шаблон:Gli in size, form, or behavior and which is responsible for determining the sex of an organism. In humans, the Шаблон:Gli and the Шаблон:Gli are sex chromosomes.
A common structural Шаблон:Gli in the secondary structures of Шаблон:Gli consisting of a right-handed helix conformation resulting from hydrogen bonding between Шаблон:Gli residues which are not immediately adjacent to each other.
A regulated phenomenon of eukaryotic Шаблон:Gli in which specific Шаблон:Gli or parts of exons from the same Шаблон:Gli are variably included within or removed from the final, mature Шаблон:Gli transcript. A class of Шаблон:Gli, alternative splicing allows a single Шаблон:Gli to code for multiple protein Шаблон:Gli and greatly increases the diversity of proteins that can be produced by an individual Шаблон:Gli. See also Шаблон:Gli.
Any of a class of organic compounds whose basic structural formula includes a central carbon atom bonded to amine and carboxylfunctional groups and to a variable side chain. Out of nearly 500 known amino acids, a set of 20 are coded for by the Шаблон:Gli and incorporated into long polymeric chains as the building blocks of Шаблон:Gli and hence of Шаблон:Gli and Шаблон:Gli. The specific sequences of amino acids in the polypeptide chains that form a protein are ultimately responsible for determining the protein's structure and function.
Every Шаблон:Gli has the same basic structural formula, consisting of a central carbon atom (α) bonded to three major substituents: one amino group (blue), one carboxyl group (red), and one variable side chain (green). The side chain, which can range from a simple methyl group (alanine) to more complex functional groups such as a double-ringed indole (tryptophan), gives each particular amino acid its unique identity. During Шаблон:Gli, amino acids are joined into a linear chain by condensation reactions which create Шаблон:Gli between the carboxyl group of one amino acid and the amino group of an adjacent amino acid. The first and last amino acids in the chain are said to be Шаблон:Gli and Шаблон:Gli, respectively, in reference to the unbonded amino group of the first amino acid and the unbonded carboxyl group of the last.
Any of a set of enzymes which catalyze the transesterification reaction that results in the attachment of a specific Шаблон:Gli (or a precursor) to one of its cognate Шаблон:Gli molecules, forming an Шаблон:Gli. Each of the 20 different amino acids used in the Шаблон:Gli is recognized and attached by its own specific synthetase enzyme, and most synthetases are cognate to several different tRNAs according to their specific Шаблон:Gli.
Any DNA or RNA sequence or fragment that is the source and/or product of an Шаблон:Gli reaction. The term is most frequently used to describe the numerous copied fragments that are the products of the Шаблон:Gli or Шаблон:Gli, though it may also refer to sequences that are amplified naturally within a genome, e.g. by Шаблон:Gli.
The Шаблон:Gli of a biomolecule, in particular the production of one or more copies of a Шаблон:Gli, known as an Шаблон:Gli, either naturally (e.g. by spontaneous Шаблон:Gli) or artificially (e.g. by Шаблон:Gli), and especially implying many repeated replication events resulting in thousands, millions, or billions of copies of the target sequence, which is then said to be amplified.
Any Шаблон:Gli reaction or process in which energy is expended in order to build complex substances such as macromolecules from simpler compounds, including aspects of growth and biosynthesis. Anabolic processes and Шаблон:Gli tend to involve reductive steps that create high-enthalpy, low-entropy compounds such as proteins and nucleic acid polymers.[3] Contrast Шаблон:Gli.
2. Describing an organism that is able to survive and grow in the absence of diatomic oxygen, or a pathway or process characterized by the absence of diatomic oxygen; e.g. Шаблон:Gli.[3]
The failure of one or more pairs of Шаблон:Gli or Шаблон:Gli to properly migrate to opposite sides of the cell during Шаблон:Gli of Шаблон:Gli or Шаблон:Gli due to a defective Шаблон:Gli. Consequently, both daughter cells are Шаблон:Gli: one is missing one or more chromosomes (creating a Шаблон:Gli) while the other has one or more extra copies of the same chromosomes (creating a Шаблон:Gli).
The condition of a cell or organism having an abnormal number of one or more particular Шаблон:Gli (but excluding abnormal numbers of complete sets of chromosomes, which instead is known as Шаблон:Gli).
The Шаблон:Gli of two Шаблон:GliШаблон:Gli molecules containing Шаблон:Gli sequences, creating a Шаблон:Gli molecule with Шаблон:GliШаблон:Gli. The term is used in particular to describe steps in laboratory techniques such as Шаблон:Gli, where double-stranded DNA molecules are repeatedly Шаблон:Gli into single strands by heating and then exposed to cooler temperatures, causing the strands to reassociate with each other or with complementary Шаблон:Gli. The exact Шаблон:Gli is strongly influenced by the length and specific sequence of the individual strands.
A gene that confers resistance to one or more specific antibiotic compounds. In molecular cloning, Шаблон:GliШаблон:Gli are often designed to carry antibiotic resistance genes as Шаблон:Gli alongside other genes of interest, because it permits the artificial selection of successfully Шаблон:Gli cell populations when the cells are cultured in the presence of the antibiotic.
Any of a diverse family of Шаблон:Gli known as Шаблон:Gli capable of binding specifically but reversibly via non-covalent interactions to a particular Шаблон:Gli or Шаблон:Gli. Antibodies are generated as part of an organism's immune response to the introduction of a specific antigen into a host organism, and their binding of the antigen frequently (though not always) counteracts or inhibits any biological activity the antigen may have.[3] Antibodies have a characteristic Y-shaped structure consisting of a Шаблон:Gli and Шаблон:Gli held together by disulfide bonds.
A Шаблон:Gli consecutive Шаблон:Gli within a Шаблон:Gli which Шаблон:Gli the three nucleotides of a Шаблон:Gli within an Шаблон:Gli transcript. During Шаблон:Gli, each tRNA recruited to the Шаблон:Gli contains a single anticodon triplet that pairs with its complementary codon from the mRNA sequence, allowing each codon to specify a particular Шаблон:Gli to be added to the growing peptide chain. Anticodons containing Шаблон:Gli in the first position are capable of pairing with more than one codon due to a phenomenon known as Шаблон:Gli.
Any Шаблон:Gli agent that, upon introduction into an immunocompetent organism, stimulates a response from the organism's immune system that results in the production of one or more Шаблон:Gli which can bind to it specifically; in this sense the term is synonymous with Шаблон:Gli. Antigens may be pure substances, mixtures of substances, or particulate matter such as cells or cell fragments. Broader definitions may include substances that can bind to a specific antibody but are not themselves immunogenic, i.e. those which are only able to stimulate antibody production when combined with a Шаблон:Gli.[3]
A Шаблон:Gli which helps to regulate cell growth and suppress tumors when functioning correctly, such that its absence or malfunction can result in uncontrolled cell growth and possibly cancer.[7] Compare Шаблон:Gli.
The contrasting orientations of the two Шаблон:Gli of a Шаблон:GliШаблон:Gli (and more generally any pair of biopolymers) which are parallel to each other but with opposite Шаблон:Gli. For example, the two Шаблон:Gli strands of a Шаблон:Gli molecule run side-by-side but in opposite directions with respect to chemical numbering conventions, with one strand oriented Шаблон:Gli-to-Шаблон:Gli and the other 3'-to-5'.
A Шаблон:Gli which works by exchanging two different ions or small molecules across a Шаблон:Gli in opposite directions, either at the same time or consecutively.[8]
A Шаблон:GliШаблон:Gli molecule containing an Шаблон:Gli sequence that is Шаблон:Gli to a sense strand, such as a Шаблон:Gli, with which it readily Шаблон:Gli, thereby inhibiting the sense strand's further activity (e.g. Шаблон:Gli into protein). Many different classes of naturally occurring RNA such as Шаблон:Gli function by this principle, making them potent gene Шаблон:Gli in various Шаблон:Gli mechanisms. Synthetic antisense RNA has also found widespread use in gene Шаблон:Gli studies, and in practical applications such as antisense therapy.
(of a cell or organism) Lacking a Шаблон:Gli, i.e. a discrete, membrane-bound organelle enclosing the cell's Шаблон:Gli, used especially of cells which normally have a nucleus but from which the nucleus Шаблон:Gli (e.g. in artificial Шаблон:Gli), and also of specialized cell types that develop without nuclei despite that the cells of other tissues comprising the same organism ordinarily do have nuclei (e.g. mammalian erythrocytes).
The process by which contraction of the Шаблон:Gli side of a cell (and often a corresponding expansion of the opposing Шаблон:Gli side) causes the cell to assume a wedge-shaped morphology. The process is common during early development, where it is often coordinated across many adjacent cells of an Шаблон:Gli layer simultaneously in order to generate bends or folds in developing Шаблон:Gli.
The Шаблон:Gli of specific groups of cells during developmental morphogenesis allows bends and turns to form in higher-order tissues.
Any artificial Шаблон:Gli, Шаблон:Gli, or Шаблон:GliШаблон:Gli molecule, Шаблон:Gli or Шаблон:Gli, which functions as a Шаблон:Gli by binding selectively to one or more specific target molecules, usually other nucleic acids or Шаблон:Gli, and often a family of such molecules. The term is used in particular to describe short nucleic acid fragments which have been randomly generated and then artificially selected Шаблон:Gli by procedures such as SELEX. Aptamers are useful in the laboratory as Шаблон:Gli, particularly in applications where conventional protein Шаблон:Gli are not appropriate.
Any process by which chemical compounds containing biologically relevant elements (e.g. carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, selenium, iron, cobalt, nickel, copper, zinc, molybdenum, etc.) are uptaken by microorganisms and incorporated into complex Шаблон:Gli in order to synthesize various cellular components. In contrast, a Шаблон:Gli uses the energy released by decomposing exogenous molecules to power the cell's Шаблон:Gli and Шаблон:GliШаблон:Gli out of the cell, instead of reusing them to build new molecules.
In animal cells, a star-shaped system of non-Шаблон:GliШаблон:Gli that radiates from a Шаблон:Gli or from either of the poles of the Шаблон:Gli during the early stages of cell division.[8]
A single Шаблон:GliШаблон:Gli containing two or more physically attached copies of the normal Шаблон:Gli as a result of either a natural internal Шаблон:Gli or any of a variety of Шаблон:Gli methods. The resulting compound chromosome effectively carries two or more doses of all genes and sequences included on the X, yet functions in all other respects as a single chromosome, meaning that haploid 'XX' Шаблон:Gli (rather than the ordinary 'X' gametes) will be produced by Шаблон:Gli and inherited by progeny. In mechanisms such as Шаблон:Gli in which the sex of an organism is determined by the total dosage of X-linked genes, an abnormal 'XXY' Шаблон:Gli, fertilized by one XX gamete and one Y gamete, will develop into a female.
The orderly Шаблон:Gli degradation and recycling of dysfunctional or unnecessary cellular components by the cell's own enzymes as part of a carefully regulated, Шаблон:Gli-dependent pathway. Autophagic programs play important roles in nutrient-deprived and Шаблон:Gli but also help maintain homeostasis in healthy cells.
Any Шаблон:Gli that is not an Шаблон:Gli and hence is not involved in the determination of the sex of an organism. Unlike the sex chromosomes, the autosomes in a Шаблон:Gli cell exist in pairs, with the members of each pair having the same structure, morphology, and genetic Шаблон:Gli.
A cell or organism that is Шаблон:Gli for a Шаблон:Gli at which the two homologous Шаблон:Gli are identical by descent, both having been derived from a single gene in a common ancestor.[6] Contrast Шаблон:Gli.
Describing a Шаблон:Gli in which only a single species, variety, or strain is present, and which is therefore entirely free of contaminating organisms including symbiotes and parasites.
Any supernumerary Шаблон:Gli molecule which is not a duplicate of nor Шаблон:Gli to any of the standard complement of normal "A" chromosomes comprising a genome. Typically very small and devoid of structural genes, B chromosomes are by definition not necessary for life. Though they occur naturally in many eukaryotic species, they are Шаблон:Gli and thus Шаблон:Gli even between closely related individuals.[6]
A pair of two Шаблон:Gli on Шаблон:GliШаблон:Gli or Шаблон:Gli strands which are loosely attracted to each other via hydrogen bonding, a type of non-covalent electrostatic interaction between individual atoms in the purine or pyrimidine rings of the complementing bases. This phenomenon, known as base pairing, is the mechanism underlying the Шаблон:Gli that commonly occurs between nucleic acid polymers, allowing two Шаблон:Gli molecules to combine into a more energetically stable Шаблон:Gli molecule, as well as enabling certain individual strands to Шаблон:Gli. The ability of consecutive base pairs to stack one upon another contributes to the long-chain Шаблон:Gli structures observed in both Шаблон:Gli and Шаблон:Gli molecules.
A measure of the Шаблон:Gli level of a Шаблон:Gli or genes prior to a perturbation in an experiment, as in a negative control. Baseline expression may also refer to the expected or historical measure of expression for a gene.
A computer algorithm widely used in Шаблон:Gli for Шаблон:Gli and comparing primary biological sequence information such as the Шаблон:Gli of DNA or RNA or the Шаблон:Gli of proteins. BLAST programs enable scientists to quickly check for homology between two or more sequences by directly comparing the nucleotides or amino acids present at each position within each sequence; a common use is to search for matches between a specific query sequence and a digital sequence database such as a Шаблон:Gli, with the program returning a list of sequences from the database which resemble the query sequence above a specified threshold of similarity. Such comparisons can permit the identification of an organism from an unknown sample or the inference of evolutionary relationships between genes, proteins, or species.
The "standard" or classical Шаблон:Gli of the Шаблон:GliШаблон:GliШаблон:Gli, thought to represent an average of the various distinct conformations assumed by very long DNA molecules under physiological conditions.[5] The B-form double helix has a right-handed twist with a diameter of 23.7 ångströms and a Шаблон:Gli of 35.7 ångströms or about 10.5 Шаблон:Gli per full turn, such that each nucleotide pair is rotated 36° around the helical axis with respect to its neighboring pairs. See also Шаблон:Gli and Шаблон:Gli.
The Шаблон:Gli by which Шаблон:Gli molecules are Шаблон:Gli into simpler molecules, generating Шаблон:Gli in the process. This occurs via a series of enzyme-catalyzed reactions which oxidize the beta carbon of the fatty acid chain and ultimately convert it into a carbonyl group, which is then susceptible to nucleophilic attack by another molecule of Шаблон:Gli, causing thiolysis of the bond between the alpha and beta carbons; this process can be repeated to sequentially digest long chains of hydrocarbons into shorter chains, generating an additional molecule of acetyl-CoA with every cycle. In prokaryotes, beta oxidation occurs in the cytosol, while in eukaryotes it primarily takes place in the inner Шаблон:Gli membrane or in Шаблон:Gli.
The separation of a single entity (e.g. a Шаблон:Gli) into exactly two discrete entities closely resembling the original. The term refers in particular to a type of Шаблон:Gli used by Шаблон:Gli such as bacteria, whereby a single Шаблон:Gli divides evenly into two Шаблон:Gli which are genetically identical to each other and to the parent. Binary fission is preceded by Шаблон:Gli of the parent cell's DNA, rapid growth of the Шаблон:Gli, and various other processes which ensure even distribution of the cell's contents between the two progeny, but is generally a quicker and simpler process than the Шаблон:Gli and Шаблон:Gli that occur in Шаблон:Gli.
A region of a macromolecule such as a nucleic acid or a protein that directly participates in chemical interactions with another molecule. A wide variety of chemical interactions of varying strength and specificity can be described as "binding"; they may be long-term or transient, reversible or irreversible, and may rely upon relatively weak intermolecular forces or much stronger covalent bonds. Binding sites are defined by the spatial proximity of one or more particular Шаблон:Gli having functional groups with particular chemical properties. For example, the Шаблон:Gli of polypeptides in such a way that particular amino acids are positioned near each other in the protein's Шаблон:Gli may confer chemical properties that permit the interaction of those residues with a particular Шаблон:Gli. Similarly, a specific sequence of nucleobases in a DNA molecule may function as a Шаблон:Gli for a Шаблон:Gli. The precise spatial arrangement of the interacting residues and their physical accessibility to potential binding partners is critical for determining whether and how the binding site functions; thus mutations or changes in the chemical environment such as Шаблон:Gli can dramatically alter its functionality. See also Шаблон:Gli.
Any analytical method that measures or qualifies the presence, effect, or potency of a substance within or upon a biological system, either directly or indirectly, e.g. by quantifying the concentration of a particular chemical compound within a sample obtained from living organisms, cells, or tissues, and ideally under controlled conditions that compare a sample subjected to an experimental treatment with an unmanipulated sample, so as to permit inferences about the effect of the treatment upon some measured variable.[10]
The branch of Шаблон:Gli and Шаблон:Gli that studies the flow of energy through living systems, in particular how organisms acquire, produce, transform, and utilize energy in order to perform biochemical work such as Шаблон:Gli.
A community of symbiotic microorganisms, especially bacteria, where cells produce and embed themselves within a slimy, sticky Шаблон:Gli composed of various high-molecular weight biopolymers, Шаблон:Gli to each other and sometimes also to a Шаблон:Gli, which may be a biotic or abiotic surface.[11] Many bacteria can exist either as independent single cells or switch to a physiologically distinct biofilm phenotype; those that create biofilms often do so in order to shelter themselves from harmful environments. Cells residing within biofilms can easily share nutrients and Шаблон:Gli, and subpopulations of cells may Шаблон:Gli to perform specialized functions supporting the whole biofilm.[12]
A measurable indicator of some biological state, especially a compound or Шаблон:Gli whose presence or absence in a biological system is a reliable sign of a normal or abnormal process, condition, or disease.[13] Things that may serve as biomarkers include direct measurements of the concentration of a particular compound or molecule in a tissue or fluid sample, or any other characteristic physiological, histological, or radiographic signal (e.g. a change in heart rate, or a distinct Шаблон:Gli under a microscope). They are regularly used as predictive or diagnostic tools in clinical medicine and laboratory research.
Any difference in the concentration of Шаблон:Gli between two spaces within a biological system, whether Шаблон:Gli, Шаблон:Gli, across a Шаблон:Gli, or between different cells or different parts of a tissue or organ system. Gradients of one kind or another drive virtually all biochemical processes occurring within and between cells, as natural systems tend to move toward a thermodynamic equilibrium where concentrations are uniformly distributed in all spaces and no gradients exist. Gradients thus cause chemical reactions to occur in particular directions, which can be used by cells to accomplish essential biological functions, including Шаблон:Gli, Шаблон:Gli, and movement of ions and solutes into and out of cells and organelles. It is often necessary for cells to continuously regenerate gradients such as Шаблон:Gli in order to permit these processes to continue.
A term used to describe the end of a Шаблон:Gli molecule where the terminal nucleobases on each Шаблон:Gli are Шаблон:Gli with each other, such that neither strand has a single-stranded "overhang" of unpaired bases. This is in contrast to a so-called "Шаблон:Gli", where an overhang is created by one strand being one or more bases longer than the other. Blunt ends and sticky ends are relevant when Шаблон:Gli multiple DNA molecules, e.g. in Шаблон:Gli, because sticky-ended molecules will not readily Шаблон:Gli to each other unless they have matching overhangs; blunt-ended molecules do not anneal in this way, so special procedures must be used to ensure that fragments with blunt ends are joined in the correct places.
A synthetic Шаблон:Gli with a chemical structure similar to Шаблон:Gli, the only difference being the substitution of a bromine atom for the methyl group of the Шаблон:Gli.
Any of a class of Шаблон:Gli which are dependent on calcium ions (Ca2+) and whose extracellular Шаблон:Gli function as mediators of cell–cell adhesion at Шаблон:Gli in eukaryotic tissues.
An unorganized mass of parenchymal cells that forms naturally at the site of wounds in plant tissues, and which is commonly artificially induced to form in plant Шаблон:Gli as a means of initiating somatic embryogenesis.[10]
A Шаблон:Gli whose location on a chromosome is Шаблон:Gli with a particular Шаблон:Gli (often a disease-related phenotype), and which is therefore suspected of causing or contributing to the phenotype. Candidate genes are often selected for study based on a priori knowledge or speculation about their functional relevance to the trait or disease being researched.
Any of a class of organic compounds having the generic chemical formula Шаблон:Chem, and one of several major classes of Шаблон:Gli found universally in biological systems. Carbohydrates include individual Шаблон:Gli as well as larger Шаблон:GliШаблон:Gli and Шаблон:Gli, in which multiple monosaccharide monomers are joined by Шаблон:Gli.[10] Abundant and ubiquitous, these compounds are involved in numerous essential biochemical processes and Шаблон:Gli; they are widely used as an energy source for cellular Шаблон:Gli, as a form of energy storage, as Шаблон:Gli molecules, and as Шаблон:Gli to Шаблон:Gli the activity of other molecules. Carbohydrates are often colloquially described as "sugars"; the prefix glyco- indicates a compound or process containing or involving carbohydrates, and the suffix -ose usually signifies that a compound is a carbohydrate or a derivative.
1. A Шаблон:Gli that functions as a Шаблон:Gli, binding to a solute and facilitating its movement across the membrane by undergoing a series of Шаблон:Gli.[8]
3. A protein which is included in an Шаблон:Gli at high concentrations in order to prevent non-specific interactions of the assay's reagents with vessel surfaces, sample components, or other reagents.[4] For example, in many Шаблон:Gli techniques, albumin is intentionally allowed to bind non-specifically to the blotted membrane prior to Шаблон:Gli, so as to "block" potential off-target binding of the Шаблон:Gli to the membrane, which might otherwise cause background fluorescence that obscures genuine signal from the target.
A pre-existing nucleic acid sequence or construct, especially a DNA Шаблон:Gli with an annotated sequence and precisely positioned Шаблон:Gli, into which one or more Шаблон:Gli can be readily Шаблон:Gli or recombined by various Шаблон:Gli methods. Recombinant Шаблон:Gli vectors containing reliable Шаблон:Gli, Шаблон:Gli, and antibiotic resistance genes are commercially manufactured as cassettes to allow scientists to easily swap Шаблон:Gli into and out of an active "slot" or locus within the plasmid. See also Шаблон:Gli.
Any Шаблон:Gli reaction or process involving the decomposition of large or complex substances into smaller, simpler compounds, especially the breakdown of organic compounds in order to liberate energy.[3] Catabolic processes and Шаблон:Gli are usually exergonic and tend to involve oxidative steps that break chemical bonds, generating low-enthalpy, high-entropy products.[4] Contrast Шаблон:Gli.
An increase in the reaction rate of a chemical reaction due to the presence of a Шаблон:Gli.[3] A reaction whose rate is increased in this manner is said to be catalyzed. Шаблон:Gli-directed catalysis is the primary means by which many otherwise energetically unfavorable biochemical reactions occur.
Any chemical species or substance whose presence Шаблон:Gli of one or more particular chemical reactions but which is itself unchanged by the reaction, being neither a reactant nor a product of the reaction. Catalysts often need only be present in very low concentrations relative to the reactants in order for catalysis to occur.[3] They may be simple molecules which catalyze reactions spontaneously, though most biochemical reactions are catalyzed by specifically evolved Шаблон:Gli which allow them to proceed at rates millions or billions of times faster than they otherwise would.
The basic structural and functional unit of which all living organisms are composed, essentially a self-replicating ball of Шаблон:Gli surrounded by a Шаблон:Gli which separates the interior from the external environment, thus providing a protected space in which the carefully controlled chemical reactions necessary to sustain biological processes can be carried out unperturbed. Шаблон:Gli organisms are composed of a single autonomous cell, whereas Шаблон:Gli organisms consist of numerous cells cooperating together, with individual cells more or less specialized or Шаблон:Gli to serve particular functions.[4] Cells vary widely in size, shape, and substructure, particularly between Шаблон:Gli and Шаблон:Gli. The typical cell is microscopic, averaging 1 to 20 micrometres (μm) in diameter, though they may range in size from 0.1 μm to more than 20 centimetres in diameter for the eggs laid by some birds and reptiles, which are highly specialized single-celled ova.[10]
The branch of biology that studies the structures, functions, processes, and properties of biological Шаблон:Gli, the self-contained units of life common to all living organisms.
A specialized layer of Шаблон:Gli proteins lining the inner face of the Шаблон:Gli in most eukaryotic cells, composed primarily of Шаблон:GliШаблон:Gli and Шаблон:GliШаблон:Gli and usually 100–1000 nanometres thick, which functions as a modulator of membrane behavior and cell surface properties.
The process of determining the number of Шаблон:Gli within a biological sample or Шаблон:Gli by any of a variety of methods. Counting cells is an important aspect of Шаблон:Gli used widely in research and clinical medicine. It is generally achieved by using a manual or digital Шаблон:Gli to count the number of cells present in small fractions of a sample, and then extrapolating to estimate the total number present in the entire sample. The resulting quantification is typically expressed as a density or concentration, i.e. the number of cells per unit area or volume.
The process by which living cells are grown and maintained, or "cultured", under carefully controlled conditions, generally outside of their natural environment. Optimal growth conditions vary widely for different cell types but usually consist of a suitable vessel (e.g. a Шаблон:Gli or Шаблон:Gli) containing a specifically formulated Шаблон:Gli or Шаблон:Gli that supplies all of the nutrients essential for life (Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, minerals, etc.) plus any desirable growth factors and Шаблон:Gli, permits gas exchange (if necessary), and regulates the environment by maintaining consistent physico-chemical properties (temperature, Шаблон:Gli, osmotic pressure, etc.). Some cell types require a solid surface to which they can Шаблон:Gli in order to reproduce, whereas others can be grown while floating freely in a liquid or gelatinous Шаблон:Gli. Most cells have a genetically determined reproduction limit, but Шаблон:Gli cells will divide indefinitely if provided with optimal conditions.
The separation of an individual Шаблон:Gli into two Шаблон:Gli by any process. Cell division generally occurs by a complex, carefully structured sequence of events involving the reorganization of the parent cell's internal contents, the physical Шаблон:Gli of the Шаблон:Gli and Шаблон:Gli, and the even distribution of contents between the two resulting cells, so that each ultimately contains approximately half of the original cell's starting material. It usually implies reproduction via the Шаблон:Gli of the parent cell's genetic material prior to division, though cells may also divide without replicating their DNA. In prokaryotic cells, Шаблон:Gli is the primary form of cell division. In eukaryotic cells, asexual division occurs by Шаблон:Gli and Шаблон:Gli, while specific cell types reserved for sexual reproduction can additionally divide by Шаблон:Gli.[8]
The merging or coalescence of two or more cells into a single cell, as occurs in the fusion of Шаблон:Gli to form a Шаблон:Gli. Generally this occurs by the destabilization of each cell's Шаблон:Gli and the formation of Шаблон:Gli bridges between them which then expand until the two cytoplasms are completely mixed; intercellular structures or Шаблон:Gli such as Шаблон:Gli may or may not fuse as well. Some cells can be artificially induced to fuse with each other by treating them with a fusogen such as polyethylene glycol or by passing an electric current through them.[10]
The selectively permeable Шаблон:Gli surrounding all prokaryotic and eukaryotic cells, defining the outermost boundary of the cell and physically separating the Шаблон:Gli from the Шаблон:Gli environment.[14] Like all membranes, the cell membrane is a flexible, fluid, sheet-like Шаблон:Gli with Шаблон:Gli, Шаблон:Gli, and numerous other molecules embedded within or interacting with it from both sides. Embedded molecules often have Шаблон:Gli alongside the membrane's lipids. Though the cell membrane can be freely crossed by many ions, small organic molecules, and water, most other substances require Шаблон:Gli through special pores or Шаблон:Gli or by Шаблон:Gli or Шаблон:Gli in order to enter or exit the cell, especially very large or electrically charged molecules such as proteins and nucleic acids. Besides regulating the transport of substances into and out of the cell, the cell membrane creates an organized interior space in which to perform life-sustaining activities and plays fundamental roles in all of the cell's interactions with its environment, making it important in Шаблон:Gli, Шаблон:Gli, defense, and Шаблон:Gli, among numerous other processes.
Cross-sectional diagram of a typical eukaryotic Шаблон:Gli
The study of the various biological activities and biochemical processes which sustain life inside Шаблон:Gli, particularly (but not necessarily limited to) those related to Шаблон:Gli and energy transfer, growth and Шаблон:Gli, and the ordinary processes of the Шаблон:Gli.
The spatial variation within a Шаблон:Gli, i.e. the existence of differences in shape, structure, or function between different parts of the same cell. Almost all Шаблон:Gli exhibit some form of polarity, often along an invisible axis which defines opposing sides or poles where the variation is most extreme. Having internal polarity permits cells to accomplish specialized functions such as Шаблон:Gli or to serve as Шаблон:Gli cells which must perform different tasks on different sides, or facilitates Шаблон:Gli or Шаблон:Gli.
The diverse set of processes by which cells transmit information to and receive information from themselves, from other cells, or from their surroundings. Шаблон:Gli occurs in all cell types, prokaryotic and eukaryotic, and is of critical importance to the cell's ability to navigate and survive its physical environment. Countless mechanisms of signaling have evolved in different organisms and are often categorized according to the proximity between sender and recipient (Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, or Шаблон:Gli).
Any of a class of Шаблон:Gli proteins embedded within or attached to the external surface of the Шаблон:Gli, with one or more Шаблон:Gli facing the Шаблон:Gli environment and one or more Шаблон:Gli that couple the binding of a particular Шаблон:Gli to an Шаблон:Gli event or process. Cell surface receptors are a primary means by which environmental signals are received by the cell and Шаблон:Gli across the membrane into the cell interior. Some may also bind exogenous ligands and transport them into the cell in a process known as Шаблон:Gli.[15]
A tough, variously flexible or rigid layer of Шаблон:Gli or Шаблон:Gli polymers surrounding some cell types immediately outside of the Шаблон:Gli, including plant cells and most Шаблон:Gli, which functions as an additional protective and selective barrier and gives the cell a definite shape and structural support. The chemical composition of the cell wall varies widely between taxonomic groups, and even between different stages of the Шаблон:Gli: in land plants it consists primarily of cellulose, hemicellulose, and pectin, while algae make use of carrageenan and agar, fungi use chitin, and bacterial cell walls contain Шаблон:Gli.
A unit for measuring Шаблон:Gli defined as the distance between chromosomal Шаблон:Gli for which the expected average number of intervening Шаблон:Gli in a single generation is 0.01. Though not an actual measure of physical distance, it is used to infer the actual distance between two loci based on the apparent likelihood of a crossover occurring between them in any given Шаблон:Gli division.
A generalized framework for understanding the flow of genetic information between macromolecules within biological systems. The central dogma outlines the fundamental principle that the sequence information encoded in the three major classes of biopolymer—Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli—can only be transferred between these three classes in certain ways, and not in others: specifically, information transfer between the Шаблон:Gli and from nucleic acid to protein is possible, but transfer from protein to protein, or from protein back to either type of nucleic acid, is impossible and does not occur naturally.
Possible types of information transfer according to the Шаблон:Gli. Three general transfers, in red, occur routinely in all living cells: DNA-to-DNA (Шаблон:Gli), DNA-to-RNA (Шаблон:Gli), and RNA-to-protein (Шаблон:Gli). Three special transfers, in blue, are known to occur only in viruses or in the laboratory: RNA-to-RNA (Шаблон:Gli), RNA-to-DNA (Шаблон:Gli), and DNA-to-protein (direct translation without an mRNA intermediate). An additional three transfers are believed not to be possible at all: protein-to-protein, protein-to-RNA, and protein-to-DNA—though it has been argued that there are exceptions by which all three can occur.
A cylindrical Шаблон:Gli composed of Шаблон:Gli, present only in certain eukaryotes. A pair of centrioles migrate to and define the two opposite poles of a Шаблон:Gli where, as part of a Шаблон:Gli, they initiate the growth of the Шаблон:Gli.
A specialized DNA sequence within a Шаблон:Gli that links a pair of Шаблон:Gli. The primary function of the centromere is to act as the site of assembly for Шаблон:Gli, protein complexes which direct the attachment of Шаблон:Gli to the centromere and facilitate Шаблон:Gli of the chromatids during Шаблон:Gli or Шаблон:Gli.
The proportion of the total length of a Шаблон:Gli encompassed by its Шаблон:Gli, typically expressed as a percentage; e.g. a chromosome with a centromeric index of 15 is Шаблон:Gli, with a short arm comprising only 15% of its overall length.[6]
A type of Шаблон:Gli whose shape forms an aqueous pore in a Шаблон:Gli, permitting the passage of specific solutes, often small ions, across the membrane in either or both directions.[8]
A set of axioms which state that, in the Шаблон:Gli of any chromosome, species, or organism, the total number of Шаблон:Gli (Шаблон:Font) Шаблон:Gli will be approximately equal to the total number of Шаблон:Gli (Шаблон:Font) residues, and the number of Шаблон:Gli (Шаблон:Font) residues will be equal to the number of Шаблон:Gli (Шаблон:Font) residues; accordingly, the total number of Шаблон:Gli (Шаблон:Font + Шаблон:Font) will equal the total number of Шаблон:Gli (Шаблон:Font + Шаблон:Font). These observations illustrate the highly specific nature of the Шаблон:GliШаблон:Gli that occurs in all Шаблон:Gli DNA molecules: even though non-standard pairings are technically possible, they are exceptionally rare because the standard ones are strongly favored in most conditions. Still, the 1:1 equivalence is seldom exact, since at any given time nucleobase ratios are inevitably distorted to some small degree by Шаблон:GliШаблон:Gli, missing bases, and non-canonical bases. The presence of Шаблон:Gli polymers also alters the proportions, as an individual Шаблон:Gli may contain any number of any of the bases.
A non-directional, random change in the movement of a molecule, cell, or organism in response to a chemical stimulus, e.g. a change in speed resulting from exposure to a particular chemical compound.
A directed, non-random change in the movement of a molecule, cell, or organism in response to a chemical stimulus, e.g. towards or away from an area with a high concentration of a particular chemical compound.[8]
A cross-shaped junction that forms the physical point of contact between two non-sister Шаблон:Gli belonging to Шаблон:Gli during Шаблон:Gli. As well as ensuring proper Шаблон:Gli of the chromosomes, these junctions are also the Шаблон:Gli at which Шаблон:Gli may occur during Шаблон:Gli or Шаблон:Gli, which results in the reciprocal exchange of DNA between the synapsed chromatids.
The presence of two or more populations of cells with distinct Шаблон:Gli in an individual organism, known as a chimera, which has developed from the fusion of cells originating from separate Шаблон:Gli; each population of cells retains its own genome, such that the organism as a whole is a mixture of genetically non-identical tissues. Genetic chimerism may be inherited (e.g. by the fusion of multiple embryos during pregnancy) or acquired after birth (e.g. by allogeneic transplantation of cells, tissues, or organs from a genetically non-identical donor); in plants, it can result from grafting or errors in cell division. It is similar to but distinct from Шаблон:Gli.
A type of small, lens-shaped Шаблон:GliШаблон:Gli found in the cells of green algae and plants which contains light-sensitive photosynthetic pigments and in which the series of biochemical reactions that comprise photosynthesis takes place. Like Шаблон:Gli, chloroplasts are bound by a double membrane, contain their own Шаблон:Gli from which they direct transcription of a unique set of genes, and replicate independently of the nuclear genome.[10][4]
The set of Шаблон:Gli molecules contained within Шаблон:Gli, a type of photosynthetic Шаблон:GliШаблон:Gli located within the cells of some eukaryotes such as plants and algae, representing a semi-autonomous Шаблон:Gli separate from that within the cell's nucleus. Like other types of plastid DNA, cpDNA usually exists in the form of small circular Шаблон:Gli.
A chemical compound that is the principal sterol biosynthesized by animal cells and an essential component of Шаблон:Gli, in which it serves to buffer the membrane's Шаблон:Gli and plays roles in Шаблон:Gli. It is produced primarily in tissues of the liver and the nervous system, and is transported in an esterified form by Шаблон:Gli in the blood plasma.[4]
One copy of a newly copied Шаблон:Gli, which is joined to the original chromosome by a Шаблон:Gli. Paired copies of the same individual chromosome are known as Шаблон:Gli.
A complex of Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli found in eukaryotic cells that is the primary substance comprising Шаблон:Gli. Chromatin functions as a means of Шаблон:Gli very long DNA molecules into highly organized and densely compacted shapes, which prevents the strands from becoming tangled, reinforces the DNA during Шаблон:Gli, helps to prevent DNA damage, and plays an important role in regulating Шаблон:Gli and Шаблон:Gli.
A central amorphous mass of Шаблон:Gli found in the nuclei of cells of the salivary glands in Drosophila larvae and resulting from the fusion of Шаблон:Gli regions surrounding the Шаблон:Gli of the somatically paired chromosomes, with the distal Шаблон:Gli arms radiating outward.[6]
A region of a Шаблон:Gli that has been locally compacted or Шаблон:Gli into Шаблон:Gli, conspicuous under a microscope as a "bead", node, or dark-staining band, especially when contrasted with nearby uncompacted strings of DNA.
A Шаблон:GliШаблон:Gli molecule containing part or all of the genetic material of an organism. Chromosomes may be considered a sort of molecular "package" for carrying DNA within the Шаблон:Gli of cells and, in most eukaryotes, are composed of long strands of DNA coiled with Шаблон:Gli which bind to and Шаблон:Gli the strands to prevent them from becoming an unmanageable tangle. Chromosomes are most easily distinguished and studied in their completely condensed forms, which only occur during Шаблон:Gli. Some simple organisms have only one chromosome made of circular DNA, while most eukaryotes have multiple chromosomes made of linear DNA.
The process by which eukaryotic chromosomes become shorter, thicker, denser, and more conspicuous under a microscope during Шаблон:Gli due to systemic coiling and Шаблон:Gli of Шаблон:Gli strands of DNA in preparation for Шаблон:Gli.
A slender, thread-like, Шаблон:Gli projection extending from the surface of a eukaryotic cell, longer than a Шаблон:Gli but shorter than a Шаблон:Gli. Most eukaryotic cells have at least one primary cilium serving sensory or signaling functions; some cells employ thousands of motile cilia covering their entire surface in order to achieve locomotion or to move extracellular material past the cell.
Affecting a Шаблон:Gli or sequence on the same nucleic acid molecule. A Шаблон:Gli or sequence within a particular DNA molecule such as a Шаблон:Gli is said to be cis-acting if it influences or acts upon other sequences located within short distances (i.e. physically nearby, usually but not necessarily Шаблон:Gli) on the same molecule or chromosome; or, in the broadest sense, if it influences or acts upon other sequences located anywhere (not necessarily within a short distance) on the same chromosome of a Шаблон:Gli. Cis-acting factors are often involved in the Шаблон:Gli of Шаблон:Gli by acting to inhibit or to facilitate Шаблон:Gli. Contrast Шаблон:Gli.
A Шаблон:Gli occurring within a Шаблон:Gli (such as an Шаблон:Gli) which alters the functioning of a nearby Шаблон:Gli or genes on the same Шаблон:Gli. Cis-dominant mutations affect the Шаблон:Gli of genes because they occur at sites that control transcription rather than within the genes themselves.
Any of a class of flattened, membrane-bound Шаблон:Gli or Шаблон:Gli of the Шаблон:Gli and Шаблон:GliШаблон:Gli and the Шаблон:Gli. By traveling through one or more cisternae, each of which contains a distinct set of enzymes, newly created proteins and polysaccharides undergo chemical modifications such as Шаблон:Gli and Шаблон:Gli, which are used as packaging signals to direct their transport to specific destinations within the cell.[18]
The branch of Шаблон:Gli based solely on observation of the visible results of reproductive acts, as opposed to that made possible by the modern techniques and methodologies of Шаблон:Gli. Contrast Шаблон:Gli.
2. In Шаблон:Gli, the series of Шаблон:Gli divisions by which a Шаблон:Gli is divided, without an accompanying overall change in size, into a ball of smaller cells constituting the early Шаблон:Gli.[3]
A trough-like indentation in the surface of the Шаблон:Gli, often conspicuous when viewed through a microscope, that initiates the Шаблон:Gli of the cytoplasm (Шаблон:Gli) as the Шаблон:Gli begins to narrow during Шаблон:Gli.
The process of producing, either naturally or artificially, individual organisms or cells which are genetically identical to each other. Clones are the result of all forms of asexual reproduction, and cells that undergo Шаблон:Gli produce daughter cells that are clones of the parent cell and of each other. Cloning may also refer to biotechnology methods which artificially create copies of organisms or cells, or, in Шаблон:Gli, copies of DNA fragments or other molecules.
The strand of a double-stranded DNA molecule whose nucleotide sequence corresponds directly to that of the RNA transcript produced during Шаблон:Gli (except that Шаблон:Gli bases are substituted with Шаблон:Gli bases in the RNA molecule). Though it is not itself transcribed, the coding strand is by convention the strand used when displaying a DNA sequence because of the direct analogy between its sequence and the Шаблон:Gli of the RNA product. Contrast Шаблон:Gli; see also Шаблон:Gli.
A series of three consecutive Шаблон:Gli in a coding region of a Шаблон:Gli sequence. Each of these triplets codes for a particular Шаблон:Gli or Шаблон:Gli during Шаблон:Gli. Шаблон:Gli and Шаблон:Gli molecules are each written in a language using four "letters" (four different Шаблон:Gli), but the language used to construct proteins includes 20 "letters" (20 different amino acids). Codons provide the key that allows these two languages to be Шаблон:Gli into each other. In general, each codon corresponds to a single amino acid (or stop signal). The full set of codons is called the Шаблон:Gli.
The preferential use of a particular Шаблон:Gli to code for a particular Шаблон:Gli rather than alternative codons that are synonymous for the same amino acid, as evidenced by differences between organisms in the frequencies of the synonymous codons occurring in their coding DNA. Because the Шаблон:Gli is Шаблон:Gli, most amino acids can be specified by multiple codons. Nevertheless, certain codons tend to be overrepresented (and others underrepresented) in different species.
A relatively small, independent Шаблон:Gli which associates with a specific Шаблон:Gli and participates in the reaction(s) catalyzed by the enzyme, often by forming a covalent bond with the Шаблон:Gli. Examples include biotin, Шаблон:Gli, and Шаблон:Gli.[8]
A property of Шаблон:Glibiopolymers whereby two polymeric chains or "Шаблон:Gli" aligned Шаблон:Gli to each other will tend to form Шаблон:Gli consisting of hydrogen bonds between the individual Шаблон:Gli comprising each chain, with each type of nucleobase pairing almost exclusively with one other type of nucleobase; e.g. in Шаблон:GliШаблон:Gli molecules, Шаблон:Font pairs only with Шаблон:Font and Шаблон:Font pairs only with Шаблон:Font. Strands that are paired in such a way, and the bases themselves, are said to be complementary. The degree of complementarity between two strands strongly influences the stability of the Шаблон:Gli molecule; certain sequences may also be internally complementary, which can result in a single strand Шаблон:Gli. Complementarity is fundamental to the mechanisms governing Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli.
Шаблон:Gli that is synthesized from a single-stranded Шаблон:Gli template (typically Шаблон:Gli or Шаблон:Gli) in a reaction catalyzed by the enzyme Шаблон:Gli. cDNA is produced both naturally by retroviruses and artificially in certain laboratory techniques, particularly Шаблон:Gli. In Шаблон:Gli, the term may also be used to refer to the sequence of an mRNA transcript expressed as its DNA Шаблон:Gli counterpart (i.e. with Шаблон:Gli replacing Шаблон:Gli).
In Шаблон:Gli, a measure of the proportion of the surface area of a Шаблон:Gli that is covered by Шаблон:Gli, commonly expressed as a percentage. A culture in which the entire surface is completely covered by a continuous Шаблон:Gli, such that all cells are immediately adjacent to and in direct physical contact with other cells, with no gaps or voids, is said to be 100-percent confluent. Different cell lines may exhibit differences in morphology, growth rate, or Шаблон:Gli depending on the degree of confluence. Because of Шаблон:Gli, most show a significant reduction in the rate of Шаблон:Gli as they approach complete confluence, though some Шаблон:Gli may continue to divide, expanding vertically rather than horizontally by stacking themselves on top of the Шаблон:Gli, until all available nutrients are depleted.[10][4]
The three-dimensional spatial configuration of the atoms comprising a molecule or Шаблон:Gli structure.[10] The conformation of a Шаблон:Gli is the physical shape into which its Шаблон:Gli chains arrange themselves during Шаблон:Gli, which is not necessarily rigid and may Шаблон:Gli with the protein's particular chemical environment.
A change in the spatial Шаблон:Gli or physical shape of a molecule or macromolecule such as a protein or nucleic acid, rarely spontaneously but more commonly as a result of some alteration in the molecule's chemical environment (e.g. temperature, pH, salt concentration, etc.) or an interaction with another molecule. Changes in the Шаблон:Gli of proteins can affect whether or how strongly they bind Шаблон:Gli or Шаблон:Gli; inducing these changes is a common means (both naturally and artificially) of activating, inactivating, or otherwise controlling the function of many enzymes and receptor proteins.[4]
A calculated order of the most frequent Шаблон:Gli (of either Шаблон:Gli or Шаблон:Gli) found at each position in a common Шаблон:Gli and obtained by comparing multiple closely related sequence alignments.
A hypothetical mode of Шаблон:Gli in which the two parental Шаблон:Gli of the original Шаблон:Gli molecule ultimately remain hybridized to each other at the end of the replication process, with the two daughter strands forming their own separate molecule; hence one molecule is composed of both of the starting strands while the other is composed of the two newly synthesized strands. This is in contrast to Шаблон:Gli, in which each molecule is a hybrid of one old and one new strand. See also Шаблон:Gli.
A Шаблон:Gli or Шаблон:Gli sequence that is highly similar or identical across many species or within a Шаблон:Gli, indicating that it has remained relatively unchanged through a long period of evolutionary time.
1. The continuous Шаблон:Gli of a Шаблон:Gli, as opposed to Шаблон:Gli, in which a gene is only transcribed as needed. A gene that is transcribed continuously is called a constitutive gene.
In Шаблон:Gli, the phenomenon by which most normal eukaryotic cells Шаблон:Gli cease to grow and Шаблон:Gli upon reaching a critical cell density, usually as they approach full Шаблон:Gli or come into physical contact with other cells. As a result, many types of cells cultured on plates or in Шаблон:Gli will continue to proliferate until they cover the whole surface of the culture vessel, at which point the rate of cell division abruptly decreases or is arrested entirely, thus forming a confluent Шаблон:Gli with minimal overlap between neighboring cells, even if the nutrient medium remains plentiful, rather than stacking themselves on top of each other.[15]Шаблон:Gli or Шаблон:Gli cells tend not to respond to cell density in the same way and may continue to proliferate at high densities.[10] This type of density-dependent inhibition of growth is similar to and may occur simultaneously with, but is nonetheless distinct from, the related phenomenon of contact inhibition of movement,[4] whereby moving cells respond to physical contact by temporarily stopping and then reversing their direction of locomotion away from the point of contact.
A phenomenon observed in some Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli which have multiple Шаблон:Gli, whereby the binding of a Шаблон:Gli to one or more sites apparently increases or decreases the affinity of one or more other binding sites for other ligands. This concept highlights the sensitive nature of the chemistry that governs interactions between biomolecules: the strength and specificity of interactions between protein and ligand are influenced, sometimes substantially, by nearby interactions (often Шаблон:Gli) and by the local chemical environment in general. Cooperativity is frequently invoked to account for the non-linearity of data resulting from attempts to measure the association/dissociation constants of particular Шаблон:Gli.[4]
A phenomenon in which sections of a Шаблон:Gli are repeated and the number of Шаблон:Gli varies between individuals in the population, usually as a result of Шаблон:Gli or Шаблон:Gli events that affect entire genes or sections of chromosomes. Copy-number variations play an important role in generating Шаблон:Gli within a population.
A sequence of DNA in which a Шаблон:Gli nucleotide is immediately followed by a Шаблон:Gli nucleotide on the same Шаблон:Gli in the 5'-to-3' Шаблон:Gli; the "p" in CpG refers simply to the intervening Шаблон:Gli group linking the two consecutive nucleotides.
Any of numerous folds or Шаблон:Gli in the inner Шаблон:Gli membrane, which give this membrane its characteristic wrinkled shape and increase the surface area across which Шаблон:Gli and supporting Шаблон:Gli reactions can occur. Cristae are studded with proteins such as ATP synthase and various cytochromes.
Any chemical bond or series of bonds, normal or abnormal, natural or artificial, that connects two or more Шаблон:Gli molecules to each other, creating an even larger, often structurally rigid and mechanically durable Шаблон:Gli complex. Crosslinks may consist of covalent, ionic, or intermolecular interactions, or even extensive physical entanglements of molecules, and may be reversible or irreversible; in polymer chemistry the term is often used to describe macrostructures that form predictably in the presence of a specific reagent or catalyst. In Шаблон:Gli the usage generally implies abnormal bonding (whether naturally occurring or experimentally induced) between different Шаблон:Gli (or different parts of the same biomolecule) which are ordinarily separate, especially Шаблон:Gli and Шаблон:Gli. Crosslinking of DNA may occur between Шаблон:Gli on opposite Шаблон:Gli of a Шаблон:Gli molecule (interstrand), or between bases on the same strand (intrastrand), specifically via the formation of covalent bonds that are stronger than the hydrogen bonds of normal Шаблон:Gli; these are common targets of Шаблон:Gli pathways. Proteins are also susceptible to becoming crosslinked to DNA or to other proteins through bonds to specific surface residues, a process which is artificially induced in many laboratory methods such as Шаблон:Gli and which can be useful for studying Шаблон:Gli in their Шаблон:Gli. Crosslinks are generated by a variety of exogenous and endogenous agents, including chemical compounds and high-energy radiation, and tend to interfere with normal cellular processes such as Шаблон:Gli and Шаблон:Gli, meaning their persistence usually compromises cell health.
DNA (black) and protein (blue) can undergo Шаблон:Gli in the presence of sufficiently concentrated formaldehyde (red).
The end of a linear chain of Шаблон:Gli (i.e. a Шаблон:Gli) that is terminated by the free carboxyl group (Шаблон:Chem) of the last amino acid to be added to the chain during Шаблон:Gli. This amino acid is said to be C-terminal. By convention, sequences, domains, active sites, or any other structure positioned nearer to the C-terminus of the Шаблон:Gli or the folded Шаблон:Gli it forms relative to others are described as Шаблон:Gli. Contrast Шаблон:Gli.
The total amount of Шаблон:Gli contained within a Шаблон:GliШаблон:Gli (e.g. a Шаблон:Gli) of a particular organism or species, expressed in number of Шаблон:Gli or in units of mass (typically picograms); or, equivalently, one-half the amount in a Шаблон:GliШаблон:Gli. For simple diploid Шаблон:Gli the term is often used interchangeably with Шаблон:Gli, but in certain cases, e.g. in hybrid Шаблон:Gli descended from parents of different species, the C-value may actually represent two or more distinct Шаблон:Gli contained within the same nucleus. C-values apply only to Шаблон:Gli, and notably exclude Шаблон:Gli.
A term used to describe a diverse variety of questions regarding the immense variation in nuclear Шаблон:Gli or Шаблон:Gli among eukaryotic species, in particular the observation that genome size does not correlate with the perceived complexity of organisms, nor necessarily with the number of Шаблон:Gli they possess; for example, many single-celled protists have genomes containing thousands of times more DNA than the human genome. This was considered paradoxical until the discovery that eukaryotic genomes consist mostly of Шаблон:Gli, which lacks genes by definition. The focus of the enigma has since shifted to understanding why and how eukaryotic genomes came to be filled with so much non-coding DNA, and why some genomes have a higher gene content than others.
The study of the morphology, processes, and life history of living Шаблон:Gli, particularly by means of light and electron microscopy.[10] The term is also sometimes used as a synonym for the broader field of Шаблон:Gli.
The interdisciplinary field that studies Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli at the level of an individual cell by making use of single-cell molecular techniques and advanced microscopy to visualize the interactions of cellular components Шаблон:Gli.[19]
All of the material contained within a Шаблон:Gli excluding (in eukaryotes) the Шаблон:Gli;[8][4] i.e. that part of the Шаблон:Gli which is enclosed by the Шаблон:Gli but separated from the Шаблон:Gli by the Шаблон:Gli, consisting of the fluid Шаблон:Gli and the totality of its contents, including all of the cell's internal Шаблон:Gli, Шаблон:Gli, and substructures such as Шаблон:Gli, Шаблон:Gli, the Шаблон:Gli, Шаблон:Gli and Шаблон:Gli, and a network of filamentous Шаблон:Gli known as the Шаблон:Gli.[10] Some definitions of cytoplasm exclude certain organelles such as Шаблон:Gli and Шаблон:Gli. Composed of about 80 percent water, the numerous small molecules and macromolecular complexes dissolved or suspended within the cytoplasm give it characteristic viscoelastic and thixotropic properties, allowing it to behave variously as a gel or a liquid solution.[15] Though continuous throughout the intracellular space, the cytoplasm can often be resolved into distinct phases of different density and composition, such as an Шаблон:Gli and Шаблон:Gli.[15] Most of the metabolic and biosynthetic activities of the cell take place in the cytoplasm, including Шаблон:Gli by Шаблон:Gli. Despite their physical separation, the cytoplasm and the nucleus are mutually dependent upon each other, such that an isolated nucleus without cytoplasm is as incapable of surviving for long periods as is the Шаблон:Gli.[15]
The flow of the Шаблон:Gli inside a cell, driven by forces exerted upon cytoplasmic fluids by the Шаблон:Gli. This flow functions partly to speed up the transport of molecules and Шаблон:Gli suspended in the cytoplasm to different parts of the cell, which would otherwise have to rely on passive diffusion for movement. It is most commonly observed in very large eukaryotic cells, for which there is a greater need for transport efficiency.
An Шаблон:Gli eukaryotic cell; or all other cellular components besides the nucleus (i.e. the cell membrane, cytoplasm, organelles, etc.) considered collectively. The term is most often used in the context of Шаблон:Gli experiments, during which the cytoplast can sometimes remain viable in the absence of a nucleus for up to 48 hours.[15]
A Шаблон:Gli resulting from the Шаблон:Gli of an initial progenitor, known as the Шаблон:Gli. Generally two daughter cells are produced per division.[10]
A spontaneous Шаблон:Gli in the genome of an individual organism that is new to that organism's lineage, having first appeared in a Шаблон:Gli of one of the organism's parents or in the fertilized egg that develops into the organism; i.e. a mutation that was not present in either parent's genome.[6]
The assembly of a synthetic Шаблон:Gli from free Шаблон:Gli without relying on an existing Шаблон:Gli, i.e. de novo, by any of a variety of laboratory methods. De novo synthesis makes it theoretically possible to construct completely Шаблон:Gli with no naturally occurring equivalent, and no restrictions on size or sequence. It is performed routinely in the commercial production of customized, made-to-order Шаблон:Gli sequences such as Шаблон:Gli.
The removal of an acetyl group (Шаблон:Chem) from a chemical compound, protein, or other biomolecule via hydrolysis of the covalent ester bond adhering it, either spontaneously or by Шаблон:Gli catalysis. Deacetylation is the opposite of Шаблон:Gli.
The release of the contents of a secretory granule (usually antimicrobial or cytotoxic molecules) into an Шаблон:Gli space by the Шаблон:Gli of the granule with the cell's plasma membrane.[4]
The removal of a methyl group (Шаблон:Chem) from a chemical compound, protein, or other biomolecule, either spontaneously or by Шаблон:Gli catalysis. Demethylation is the opposite of Шаблон:Gli; both reactions play important roles in numerous biochemical processes, including in Шаблон:Gli, as the methylation state of particular residues within particular proteins or nucleic acids can affect their structural Шаблон:Gli in a way that alters their affinity for other molecules, making transcription at nearby genetic loci more or less likely.
The process by which Шаблон:Gli or Шаблон:Gli lose their Шаблон:Gli, Шаблон:Gli, and/or Шаблон:Gli, either reversibly or irreversibly, through the application of some external chemical or mechanical stress, e.g. by heating, agitation, or exposure to a strong acid or base, all of which can disrupt intermolecular forces such as hydrogen bonding and thereby change or destroy chemical activity. Denatured proteins may be both a cause and a consequence of cell death. Denaturation may also be a normal process; the denaturation of Шаблон:Gli molecules, for example, which breaks the hydrogen bonds between Шаблон:Gli and causes the separation of the duplex molecule into two Шаблон:Gli, is a necessary step in Шаблон:Gli and Шаблон:Gli and hence is routinely performed by enzymes such as Шаблон:Gli. The same mechanism is also fundamental to laboratory methods such as Шаблон:Gli.
A Шаблон:GliШаблон:Gli sugar derived from Шаблон:Gli by the replacement of the hydroxyl group attached to the C2 carbon with a single hydrogen atom. D-deoxyribose, in its cyclic ring form, is one of three main functional groups of Шаблон:Gli and hence of Шаблон:Gli (DNA) molecules.
Шаблон:Gli differs from Шаблон:Gli only at the 2' carbon, where ribose has an oxygen atom that deoxyribose lacks (hence its name).
The removal of a Шаблон:Gli group, Шаблон:Chem, from a chemical compound, protein, or other biomolecule, either spontaneously or by Шаблон:Gli catalysis. Dephosphorylation is the opposite of Шаблон:Gli; both reactions are common molecular modifications involved in numerous biochemical pathways and processes, including in metabolism, where high-energy bonds to phosphate groups are used to transfer energy between molecules, and in the Шаблон:Gli of proteins, where the phosphorylation state of particular residues can affect the protein's affinity for other molecules or function as a Шаблон:Gli.
The artificial modification of a molecule or protein with the intent of altering its solubility or other chemical properties so as to enable analysis (e.g. by mass spectroscopy or chromatography), or of Шаблон:Gli it by attaching a detectable chemical moiety (e.g. a fluorescent tag) to make it easier to identify and track Шаблон:Gli. Molecules modified in this way are described as derivatives of their naturally occurring counterparts and are said to have been derivatized.[4]
A specialized cell junction between neighboring Шаблон:Gli cells consisting of a network of keratin filaments and structural proteins bridging the gap between the plasma membranes.[4]
In Шаблон:Gli, the fifth and final substage of Шаблон:Gli, following Шаблон:Gli and preceding Шаблон:Gli. During diakinesis, the chromosomes are further condensed, the two Шаблон:Gli reach opposite poles of the cell, and the Шаблон:Gli begins to extend from the poles to the equator.[6]
The process by which a eukaryotic cell changes from one Шаблон:Gli to another, in particular from a non-specialized Шаблон:Gli to a more specialized cell type which is then said to be differentiated. This usually occurs by a carefully regulated series of Шаблон:Gli modifications which change the specific set of Шаблон:GliШаблон:Gli by the cell, turning certain genes off and others on. These alterations to gene expression result in a cascade of Шаблон:Gli changes which can dramatically change the cell's size, shape, Шаблон:Gli, Шаблон:Gli properties, and rate of Шаблон:Gli, and therefore its functions, behaviors, and responsiveness to signals, permitting multicellular organisms to create a huge variety of functionally distinct cell types from a single Шаблон:Gli. Differentiation occurs repeatedly during an organism's development from a single-celled Шаблон:Gli into a complex multicellular system of Шаблон:Gli and cell types, and continues to some extent after the organism reaches maturity in order to repair and replace damaged and dying cells. In most cases differentiation is irreversible, though some cells may also undergo Шаблон:Gli in specific circumstances.
A molecular Шаблон:Gli consisting of exactly two covalently linked Шаблон:Gli; or any two nucleotides which are immediately adjacent to each other on the same Шаблон:Gli of a longer Шаблон:Gli polymer.
Any two or more Шаблон:Gli of a specific Шаблон:Gli occurring in the same orientation (i.e. in precisely the same order and not Шаблон:Gli) and on the same Шаблон:Gli, either separated by intervening nucleotides or not. An example is the sequence Шаблон:FontШаблон:FontШаблон:Font, in which Шаблон:Font occurs twice, though separated by six nucleotides that are not part of the repeated sequence. A direct repeat in which the repeats are immediately adjacent to each other is known as a Шаблон:Gli.
The end-to-end chemical orientation of a single linear Шаблон:Gli or Шаблон:Gli of a Шаблон:Gli polymer or a Шаблон:Gli. The nomenclature used to indicate nucleic acid directionality is based on the chemical convention of identifying individual carbon atoms in the Шаблон:Gli or Шаблон:Gli sugars of nucleotides, specifically the Шаблон:Gli and Шаблон:Gli of the Шаблон:Gli ring. The sequence of nucleotides in a polymeric chain may be read or interpreted in the 5'-to-3' direction – i.e. starting from the terminal nucleotide in which the 5' carbon is not connected to another nucleotide, and proceeding to the other terminal nucleotide, in which the 3' carbon is not connected to another nucleotide – or in the opposite 3'-to-5' direction. Most types of nucleic acid synthesis, including Шаблон:Gli and Шаблон:Gli, work exclusively in the 5'-to-3' direction, because the Шаблон:Gli involved can only catalyze the addition of free nucleotides to the open 3'-end of the previous nucleotide in the chain. Because of this, the convention when writing any nucleic acid sequence is to present it in the 5'-to-3' direction from left to right. In Шаблон:Gli nucleic acids, the two paired strands must be Шаблон:Gli in order to Шаблон:Gli with each other. Polypeptide directionality is similarly based on labeling the functional groups comprising Шаблон:Gli, specifically the amino group, which forms the Шаблон:Gli, and the carboxyl group, which forms the Шаблон:Gli; amino acid sequences are assembled in the N-to-C direction during Шаблон:Gli, and by convention are written in the same direction.
A hypothetical mode of Шаблон:Gli in which the pairing of Шаблон:Gli and newly synthesized strands is not consistent within the same daughter molecule; i.e. each of the replicated daughter molecules is a heterogeneous mixture, with some segments composed of the original template strands and others composed of the newly synthesized strands. This process implies that the pairing of strands does not occur uniformly at all Шаблон:Gli. Only the Шаблон:Gli mode of replication occurs naturally. See also Шаблон:Gli.
Any exergonic process of microbial Шаблон:Gli by which redox-active chemical species participate in oxidation-reduction reactions (exchange of electrons) to provide the cell with energy needed for sustaining Шаблон:Gli activities. External substances are absorbed by the cell from its environment and then decomposed to release energy, with the Шаблон:Gli subsequently Шаблон:Gli out of the cell. This is in contrast to an Шаблон:Gli, in which the atoms of the external substances are reused in the synthesis of biomolecules or the fabrication of cellular components.
A method of taxonomic identification in which short DNA sequences from one or more specific genes are isolated from unidentified samples and then Шаблон:Gli with sequences from a Шаблон:Gli in order to uniquely identify the species or other taxon from which the samples originated. The sequences used in the comparison are chosen carefully from genes that are both widely Шаблон:Gli and that show greater Шаблон:Gli between species than within species, e.g. the cytochrome c oxidase gene for eukaryotes or certain Шаблон:Gli genes for prokaryotes. These genes are present in nearly all living organisms but tend to evolve different mutations in different species, such that a unique sequence variant can be linked to one particular species, effectively creating a unique identifier akin to a retail barcode. DNA barcoding allows unknown specimens to be identified from otherwise indistinct tissues or body parts, where identification by morphology would be difficult or impossible, and the library of organismal barcodes is now comprehensive enough that even organisms previously unknown to science can often be Шаблон:Gli classified with confidence. The simultaneous identification of multiple different species from a mixed sample is known as metabarcoding.
A Шаблон:Gli technology used to measure Шаблон:Gli levels of Шаблон:Gli transcripts or to detect certain changes in Шаблон:Gli. It consists of an array of thousands of microscopic spots of Шаблон:GliШаблон:Gli, called features, each containing picomoles of a specific DNA sequence. This can be a short section of a Шаблон:Gli or any other DNA element, and is used as a Шаблон:Gli to hybridize a Шаблон:Gli, cRNA or Шаблон:Gli sample (called a target) under Шаблон:Gli conditions. Probe-target Шаблон:Gli is usually detected and quantified by fluorescence-based detection of Шаблон:Gli targets.
Any of a class of Шаблон:Gli which synthesize Шаблон:Gli molecules from individual Шаблон:Gli. DNA polymerases are essential for Шаблон:Gli and usually work in pairs to create identical copies of the two Шаблон:Gli of an original double-stranded molecule. They build long chains of DNA by adding nucleotides one at a time to the Шаблон:Gli of a DNA strand, usually relying on the Шаблон:Gli provided by the Шаблон:Gli strand to copy the nucleotide sequence faithfully.
The set of processes by which a cell identifies and corrects structural damage or Шаблон:Gli in the Шаблон:Gli molecules that encode its Шаблон:Gli. The ability of a cell to repair its DNA is vital to the integrity of the genome and the normal functionality of the organism.
The process by which a Шаблон:Gli molecule copies itself, producing two identical copies of one original DNA molecule. This occurs by a Шаблон:Gli involving the separation of a double-stranded molecule into two individual strands, each of which then serves as a template for the synthesis of a new strand of complementary nucleotides. Replication of Шаблон:Gli takes place during the Шаблон:Gli of Шаблон:Gli, though Шаблон:Gli molecules such as Шаблон:Gli and Шаблон:Gli may replicate independently at other times. DNA replication is the chief process by which genetic information is propagated in all living organisms and the central mechanism underlying biological inheritance.
The process of determining, by any of a variety of different methods and technologies, the order of the Шаблон:Gli in the long chain of nucleotides that constitutes a Шаблон:Gli of Шаблон:Gli.
A protein Шаблон:Gli containing at least one structural motif capable of recognizing and interacting with the Шаблон:Gli of a Шаблон:Gli or Шаблон:GliШаблон:Gli molecule. DNA-binding domains may bind to specific sequences or have a non-specific affinity for DNA. They are the primary functional components of Шаблон:Gli, including many Шаблон:Gli and regulatory proteins.
The molecular structures of several common classes of Шаблон:Gli (grey), showing how they interact with the DNA double helix (blue)
Any Шаблон:Gli or Шаблон:Gli containing one or more Шаблон:Gli capable of interacting chemically with one or more parts of a Шаблон:Gli molecule, and consequently having a specific or general affinity for Шаблон:Gli and/or Шаблон:Gli. DNA-binding activity often depends on the presence and physical accessibility of a specific nucleobase sequence, and mostly occurs at the Шаблон:Gli, since it exposes more of the functional groups which uniquely identify the bases. Binding is also influenced by the spatial conformation of the DNA chain and the occupancy of other proteins near the binding site; many proteins cannot bind to DNA without first undergoing Шаблон:Gli induced by interactions with other molecules.
A discrete, usually contiguous region of a Шаблон:Gli (or the corresponding Шаблон:Gli sequence of a Шаблон:Gli) which serves a particular function or is defined by particular physico-chemical properties (e.g. Шаблон:Gli, polar, non-polar, Шаблон:Gli, etc.),[4] and especially one which folds independently of the rest of the polypeptide into a characteristic, self-stabilizing spatial Шаблон:Gli as part of the protein's Шаблон:Gli and which contributes to or defines its biological activity. Large proteins are generally composed of multiple domains linked by short, intervening non-domain sequences.[8] Domains are commonly grouped into classes with similar properties or functions, e.g. Шаблон:Gli. More broadly, the term may also be used to refer to a discrete structural entity within any biomolecule, including functionally or compositionally distinct subregions of Шаблон:Gli and Шаблон:Gli.[15]
Any mechanism by which organisms neutralize the large difference in Шаблон:Gli caused by the presence of differing numbers of Шаблон:Gli in the different sexes, thereby equalizing the Шаблон:Gli of sex-linked genes so that the members of each sex receive the same or similar amounts of the Шаблон:Gli of such genes. An example is Шаблон:Gli in female mammals.
The shape most commonly assumed by Шаблон:GliШаблон:Gli molecules, resembling a ladder that has been twisted upon its long axis, with the rungs of the ladder consisting of Шаблон:GliШаблон:Gli. This Шаблон:Gli is the most energetically stable conformation of the double-stranded forms of both Шаблон:Gli and Шаблон:Gli under most naturally occurring conditions, arising as a consequence of the Шаблон:Gli of the Шаблон:Gli and the stacking of the Шаблон:Gli bonded to it. In Шаблон:Gli, the most common DNA variant found in nature, the double helix has a right-handed twist with about 10 base pairs per full turn, and the molecular geometry results in an alternating pattern of "grooves" of differing widths (a Шаблон:Gli and a Шаблон:Gli) between the parallel backbones.
Double-stranded DNA most commonly exists in the shape of a Шаблон:Gli.
The loss of continuity of the Шаблон:Gli in both strands of a Шаблон:Gli molecule, in particular when the two breaks occur at sites that are directly across from or very close to each other on the complementary strands.[15] Contrast Шаблон:Gli.
Any Шаблон:Gli molecule that is composed of two Шаблон:Gli, Шаблон:GliШаблон:Gli polymers, known as Шаблон:Gli, which are bonded together by hydrogen bonds between the complementary Шаблон:Gli. Though it is possible for DNA to exist as a Шаблон:Gli, it is generally more stable and more common in double-stranded form. In most cases, the complementary Шаблон:Gli causes the twin strands to coil around each other in the shape of a Шаблон:Gli.
Any Шаблон:Gli molecule that is composed of two Шаблон:Gli, Шаблон:GliШаблон:Gli polymers, known as Шаблон:Gli, which are bonded together by hydrogen bonds between the complementary Шаблон:Gli. Though RNA usually occurs in Шаблон:Gli, it is also capable of forming duplexes in the Шаблон:Gli; an example is an Шаблон:Gli transcript pairing with an Шаблон:Gli of the same transcript, which effectively Шаблон:Gli the gene from which the mRNA was transcribed by preventing translation. As in dsDNA, the Шаблон:Gli in dsRNA usually causes the twin strands to coil around each other in the shape of a Шаблон:Gli.
Any process, natural or artificial, which decreases the level of Шаблон:Gli of a certain Шаблон:Gli. A gene which is observed to be expressed at relatively low levels (such as by detecting lower levels of its Шаблон:Gli transcripts) in one sample compared to another sample is said to be downregulated. Contrast Шаблон:Gli.
The production of a second copy of part or all of a Шаблон:Gli or Шаблон:Gli, either naturally or artificially, and the retention of both copies; especially when both the copy and the original sequence are retained Шаблон:Gli within the same molecule, often but not necessarily Шаблон:Gli to each other. See also Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli.
The abnormal growth or development of a Шаблон:Gli or organ; a change in the growth, behavior, or organization of cells within a tissue, or the presence of cells of an abnormal type, such that the tissue becomes disordered,[8] an event which often precedes the development of cancer.
Any small molecule or Шаблон:Gli which by interacting with a particular Шаблон:Gli changes its catalytic activity but is not itself changed. A positive effector enhances the enzyme's activity while a negative effector reduces it.[3]
The process by which electrons are transferred from electron donors to electron acceptors via a stepwise series of redox reactions carried out by dedicated Шаблон:Gli and Шаблон:Gli, especially as a component of Шаблон:Gli which convert chemical energy from food into a form that is readily accessible by the cell. Most electron transport chains begin by oxidizing molecules derived from Шаблон:Gli such as Шаблон:Gli and Шаблон:Gli, converting them into a series of intermediate compounds via a specific sequence of independently catalyzed reactions, with the products of the previous reaction used as reactants in the next reaction until ultimately reaching a terminal electron acceptor. The particular compounds used as donors, intermediates, and acceptors vary widely between organisms and cell types; in Шаблон:Gli, the terminal acceptor is diatomic oxygen (Шаблон:Chem), whereas Шаблон:Gli uses other acceptors. In all variants, the free energy released by these reactions is coupled to the Шаблон:Gli pumping of protons (Шаблон:Chem) across a membrane in order to generate an electrochemical gradient which is then used to drive the production of Шаблон:Gli, a process known as Шаблон:Gli. In eukaryotes, electron transport chains are conducted by proteins embedded within the membranes of Шаблон:Gli and Шаблон:Gli, while in prokaryotes the relevant proteins are embedded within the Шаблон:Gli.
A schematic layout of the Шаблон:Gli as it occurs in most animal mitochondria: Шаблон:Gli and Шаблон:Gli supplied by the Шаблон:Gli donate their electrons to an enzyme embedded within the inner mitochondrial membrane, from which the electrons are then transferred through a series of other embedded enzymes, all of which use the free energy gained to pump protons into the intermembrane space, against their concentration gradient. The pressure to restore electrochemical equilibrium by Шаблон:Gli across the membrane is exploited by Шаблон:Gli, which uses the free energy to catalyze the addition of a phosphate group to Шаблон:Gli, converting it to Шаблон:Gli.
The physical separation of molecules, e.g. Шаблон:Gli or Шаблон:Gli, according to their movement through a fluid medium to which an electric field is applied, where the distance they travel is proportional to their size. Because of their negatively charged Шаблон:Gli, nucleic acids are repelled by the negative electrode at one end of the medium and attracted to the positive electrode at the other end, which causes them to be pulled toward the latter over time; Шаблон:Gli proteins and even whole cells may migrate through the medium in a similar manner. The speed at which the molecules migrate depends on their net electric charge and is inversely proportional to their overall size (i.e. the number of atoms they contain), such that very small molecules tend to move faster through the medium than very large molecules. Thus electrophoretic techniques, particularly Шаблон:Gli with agarose or polyacrylamide-based gels as the supporting medium, are widely used in molecular biology laboratories to quickly and conveniently isolate molecules of interest from heterogeneous mixtures and/or identify them based on their expected molecular weight. Reference markers containing molecules of known weight are commonly run alongside unknown samples to aid size-based identification. Electrophoresis is often combined with other techniques such as Шаблон:Gli.[10]
A molecular biology technique in which a strong electric field is applied to living cells in order to temporarily increase the permeability of their cell membranes, allowing exogenous nucleic acids, proteins, or chemical compounds to easily pass through the membrane and thereby enter the cells. It is a common method of achieving Шаблон:Gli and Шаблон:Gli.
The developing organism that represents the earliest stages of Шаблон:Gli in all sexually reproducing Шаблон:Gli organisms, traditionally encompassing the period after Шаблон:Gli of an egg cell and formation of the Шаблон:Gli but prior to birth, hatching, or metamorphosis. During this period, known as embryonic development, the single-cell zygote is transformed by repeated Шаблон:Gli and rearrangements into a series of increasingly complex multicellular structures. For humans, the term "embryo" is only used until the ninth week after conception, after which time the embryo is known as a foetus; for most other organisms, including plants, "embryo" can be used more broadly to describe any early stage of the life cycle.
Any process by which a substance is Шаблон:Gli uptaken by or brought inside of a Шаблон:Gli, crossing the Шаблон:Gli from an Шаблон:Gli into an Шаблон:Gli, which includes the subclasses of Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli processes. All of these involve surrounding an extracellular molecule, protein, or even another cell or organism with an extension or Шаблон:Gli of the cell membrane, which then "buds off" or separates from the rest of the membrane on the cytoplasmic side, forming a membrane-enclosed Шаблон:Gli containing the ingested materials. By this mechanism the material can cross the Шаблон:Gli without being exposed to the hydrophobic space in between, instead remaining suspended in the fluid of the extracellular space. Many large, polar macromolecules which cannot simply diffuse across the membrane, such as Шаблон:Gli and Шаблон:Gli, are transported into the cell by endocytosis. It is distinguished from alternative routes such as passing through Шаблон:Gli or being chaperoned by Шаблон:Gli. The reverse process is called Шаблон:Gli.
Originating or arising inside of an organism or cell; produced by the organism or cell itself, rather than sourced from the external environment; of or pertaining to native or internal factors or processes, to be distinguished from foreign or Шаблон:Gli factors or processes.[3]
Any Шаблон:Gli whose activity is to cleave Шаблон:Gli within a chain of Шаблон:Gli, including those that cleave relatively nonspecifically (without regard to Шаблон:Gli) and those that cleave only at very specific sequences (so-called Шаблон:Gli). When recognition of a specific sequence is required, endonucleases make their cuts in the middle of the sequence. Contrast Шаблон:Gli.
The irregular network of unit membranes, continuous with the Шаблон:Gli, that extends from the Шаблон:Gli into the Шаблон:Gli in most eukaryotic cells, where it serves important packaging and transport functions for newly synthesized macromolecules. The membranes interweave to form a mesh of tubular channels and flattened sacs called Шаблон:Gli which house a variety of enzymes that perform Шаблон:Gli including Шаблон:Gli proteins for Шаблон:Gli. The outer surfaces of so-called Шаблон:Gli are studded with attached Шаблон:Gli that serve as sites of protein synthesis, whereas Шаблон:Gli, lacking ribosomes, functions in the synthesis of Шаблон:Gli and steroid hormones and in the detoxification of metabolic wastes.[3] Generally both types of ER occur together, though some cell types are characterized by different proportions of rough and smooth ER, depending on the activities of the cell.
Any of a class of intracellular Шаблон:Gli which serve transportation and sorting functions in eukaryotic cells as part of the Шаблон:Gli. They are formed when proteins or other macromolecules enter the cytoplasm inside Шаблон:Gli invaginated from the Шаблон:Gli or the Шаблон:Gli by Шаблон:Gli, after which they are shuttled across the cell to various destinations; e.g. endosomes carrying foreign molecules often fuse with Шаблон:Gli, where the contents are then degraded.
A subclass of Шаблон:Gli transcribed from regions of DNA containing Шаблон:Gli sequences. The expression of a given eRNA generally correlates with the activity of the corresponding enhancer in enhancing transcription of its target genes, suggesting that eRNAs play an active role in gene regulation Шаблон:Gli or Шаблон:Gli.
To artificially remove the Шаблон:Gli from a Шаблон:Gli, e.g. by micromanipulation in the laboratory or by destroying it through irradiation with ultraviolet light, rendering the cell Шаблон:Gli.[10]
A Шаблон:Gli which acts as a Шаблон:Gli for a biological process by accelerating a specific chemical reaction, typically by binding one or more Шаблон:Gli molecules and decreasing the activation energy necessary for the initiation of a particular reaction involving the substrate(s). Enzymatic catalysis often results in the chemical conversion of the substrate(s) into one or more products, which then inhibit or permit subsequent reactions. All Шаблон:Gli consist of a series of individual reactions which each depend upon one or more specific enzymes to drive them forward at rates fast enough to sustain life.
A Шаблон:Gli designed to detect the presence of a particular Шаблон:Gli or Шаблон:Gli in a liquid sample using Шаблон:Gli conjugated to Шаблон:Gli capable of specifically binding the antigen. The antigen of interest is usually first immobilized by adhering to a solid support (e.g. a polystyrene microtiter plate), then one or more antigen-specific antibodies covalently bonded to a particular enzyme are added and any unbound antibody is washed away; when the attached enzyme's Шаблон:Gli is subsequently added, the reaction between enzyme and substrate produces a detectable, quantifiable change in some measurable Шаблон:Gli (often a color change), thus reporting the presence of the targeted antigen in the sample. ELISA techniques are widely used as diagnostic tools in clinical medicine and academic research, as well as a form of quality control in many biotechnology industries.
1. Another name for a Шаблон:Gli, especially one that is capable of integrating into a Шаблон:Gli.
2. In eukaryotes, any non-integrated Шаблон:Gli circular Шаблон:Gli molecule that is stably maintained and replicated in the Шаблон:Gli simultaneously with the rest of the host cell. Such molecules may include viral genomes, bacterial plasmids, and aberrant chromosomal fragments.
The collective action of multiple genes interacting during Шаблон:Gli. A form of gene action, epistasis can be either additive or multiplicative in its effects on specific Шаблон:Gli.
The specific site or region within an Шаблон:GliШаблон:Gli such as a Шаблон:Gli or Шаблон:Gli which is recognized by B or T cells of the immune system, against which a specific Шаблон:Gli is produced, and with which the antibody's Шаблон:Gli specifically interacts or binds. In proteins, epitopes are typically Шаблон:Gli of 4–5 amino acid residues, sequential or discontiguous, which by virtue of the distinct spatial Шаблон:Gli they adopt upon Шаблон:Gli are able to uniquely interact with a particular paratope. In this sense they may be considered Шаблон:Gli, though they do not necessarily overlap with ligand binding sites and need not be in any way relevant to the protein's normal function. Very large molecules may have multiple epitopes, each of which is recognized by a different antibody.
A relatively open, lightly compacted form of Шаблон:Gli in which Шаблон:Gli is only sporadically bound in Шаблон:Gli and thus broadly accessible to binding and manipulation by Шаблон:Gli and other molecules. Euchromatic regions of a genome are often enriched in Шаблон:Gli and actively undergoing Шаблон:Gli, in contrast to Шаблон:Gli, which is relatively gene-poor, nucleosome-rich, and less accessible to transcription machinery.
The condition of a cell or organism having an abnormal number of complete sets of Шаблон:Gli, possibly excluding the Шаблон:Gli. Euploidy differs from Шаблон:Gli, in which a cell or organism has an abnormal number of one or more specific individual chromosomes.
The change in the Шаблон:Gli characteristics of biological populations over successive generations. In the most traditional sense, it occurs by changes in the frequencies of Шаблон:Gli in a population's Шаблон:Gli.
Occurring outside of a cell or organism, as with observations made or experiments performed in or on cells or Шаблон:Gli which have been isolated or removed from their natural context to an external environment (usually a carefully controlled environment with minimal alteration of natural conditions, such as a Шаблон:Gli being grown in a laboratory). This is in contrast to Шаблон:Gli observations, which are made in an entirely natural context.
The enzymatic removal of a polynucleotide sequence from one or more strands of a Шаблон:Gli, or of a polypeptide sequence from a Шаблон:Gli, typically implying both the breaking of the polymeric molecule in two locations and the subsequent rejoining of the two breakpoints after the sequence between them has been removed. The term may be used to describe a wide variety of processes performed by distinct enzymes, including most Шаблон:Gli and Шаблон:Gli pathways.[6]
Any Шаблон:Gli process by which a substance is secreted from or transported out of a Шаблон:Gli, crossing the Шаблон:Gli from the Шаблон:Gli into the Шаблон:Gli, especially that which occurs by the fusion of the membrane surrounding a secretory Шаблон:Gli with the larger cell membrane. This fusion causes the intra-vesicular space to merge with the extracellular fluid, releasing the vesicle's contents on the exterior side of the cell without exposing them to the hydrophobic space between the Шаблон:Gli. More narrowly the term may refer in particular to the bulk transport of a large amount of molecules out of the cell all at once, often Шаблон:Gli or Шаблон:Gli which are too large and polar to passively diffuse across the membrane themselves. The reverse process, whereby materials are invaginated into the cell, is known as Шаблон:Gli.
Originating outside of an organism or cell; of or pertaining to foreign or external factors or processes, to be distinguished from native or Шаблон:Gli factors or processes.[3]
Any part of a Шаблон:Gli that encodes a part of the final mature Шаблон:Gli produced by that gene after Шаблон:Gli have been removed by Шаблон:Gli. The term refers to both the sequence as it exists within a DNA molecule and to the corresponding sequence in RNA transcripts.
Any Шаблон:Gli whose activity is to cleave Шаблон:Gli within a chain of Шаблон:Gli, including those that cleave only upon recognition of a specific sequence (so-called Шаблон:Gli). Exonucleases make their cuts at either the Шаблон:Gli or Шаблон:Gli of the sequence (rather than in the middle, as with Шаблон:Gli).
1. (protein complex) An intracellular multi-protein complex which serves the function of degrading various types of Шаблон:Gli molecules.
2. (vesicle) A type of membrane-bound Шаблон:Gli produced in many eukaryotic cells by the inward budding of an Шаблон:Gli and the subsequent fusion of the endosome with the Шаблон:Gli, causing the release of the vesicle into various extracellular spaces, including biological fluids such as blood and saliva, where they may serve any of a wide variety of physiological functions, from waste management to intercellular signaling.
The network of interacting Шаблон:Gli and minerals secreted by and existing outside of and between cells in Шаблон:Gli structures such as Шаблон:Gli and Шаблон:Gli, forming a hydrated, mesh-like, semi-solid suspension which not only holds the cells together in an organized fashion but also provides structural and biochemical support, acting as an elastic, compressible buffer against external stresses as well as both regulating and influencing numerous aspects of cell behavior, among them Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli. The composition and properties of the ECM vary enormously between organisms and tissue types, but generally it takes the form of a Шаблон:Gli gel in which various fibrous proteins (especially collagen and elastin), enzymes, and Шаблон:Gli are embedded. Cells themselves both produce the matrix components and respond constantly to local matrix composition, a source of environmental feedback which is critical for Шаблон:Gli, tissue organization, and development.[10][22]
A type of Шаблон:Gli by which substances are conveyed across Шаблон:Gli more quickly than would be possible by ordinary passive diffusion alone, generally because Шаблон:Gli act as shuttles or pores, being arranged in such a way as to provide a Шаблон:Gli environment that is favorable for the movement of small polar molecules, which would otherwise be repulsed by the Шаблон:Gli interior of the Шаблон:Gli.[4]
The Шаблон:Gli of a Шаблон:Gli only as needed, as opposed to Шаблон:Gli, in which a gene is transcribed continuously. A gene that is transcribed as needed is called a facultative gene.
Any of a subclass of Шаблон:Gli compounds consisting of a carboxylic acid bonded to an aliphatic chain of hydrocarbons, usually 4 to 28 carbon atoms in length, which may be either saturated (containing only single bonds between the carbon atoms) or unsaturated (containing one or more double bonds). In biological systems, fatty acid chains are commonly linked to other compounds via ester bonds, primarily in Шаблон:Gli, Шаблон:Gli, and derivatives of Шаблон:Gli, all of which serve a wide variety of important cellular functions including as structural components of membranes and as energy sources in metabolic pathways.
Any Шаблон:GliШаблон:Gli in which organic molecules such as Шаблон:Gli or other carbohydrates are Шаблон:Gli in the absence of oxygen in order to produce Шаблон:Gli; or, in the broadest sense, any catabolic process in which organic compounds serve as both electron donors and acceptors.[23] This definition distinguishes fermentation from Шаблон:Gli, where inorganic diatomic oxygen (Шаблон:Chem) is the terminal electron acceptor, and from some types of Шаблон:Gli. Fermentation encompasses hundreds of different redox pathways which start and end with a huge variety of reactants and end-products, often branching from various steps in Шаблон:Gli, with the most common fermentation products being lactate, acetate, ethanol, succinate, propionate, butyrate, carbon dioxide (Шаблон:Chem), and diatomic hydrogen (Шаблон:Chem). It occurs in both prokaryotes and eukaryotes in conditions where exogenously supplied electron acceptors are unavailable, especially in oxygen-poor environments. Fermentation yields the equivalent of just 2 to 5 ATP per molecule of glucose, making it much less efficient than aerobic respiration, which can yield as much as 32 ATP per molecule of glucose. In multicellular organisms that primarily rely on aerobic respiration, such as animals, it is often employed as a contingency pathway; the term anaerobic glycolysis refers to the diversion of glycolysis intermediates to fermentation pathways when tissues cannot keep up with the demand for ATP due to insufficient oxygen supply.
A molecule exposed on the surface of a cell destined for Шаблон:Gli which is used to attract Шаблон:Gli to engulf and eliminate the cell by Шаблон:Gli. See also Шаблон:Gli.
1. (histology) The preservation of biological material by treating it with a chemical Шаблон:Gli that prevents or delays the natural postmortem processes of decay (e.g. Шаблон:Gli and putrefaction) which would otherwise eventually cause cells, tissues, and biomolecules to lose their characteristic structures and properties. Biological specimens are usually fixed with the broad objective of arresting or slowing biochemical reactions for long enough to study them in detail, essentially 'freezing' cellular processes in their natural state at a specific point in time, while minimizing disruption to existing structures and arrangements, all of which can improve subsequent Шаблон:Gli and microscopy of the fixed samples. Though fixation tends to irreversibly terminate any ongoing reactions, thus killing the fixed cells, it makes it possible to study molecular details that occur too rapidly or transiently to observe in living samples. Common fixatives such as formaldehyde work by disabling Шаблон:Gli enzymes, coagulating, insolubilizing, and/or Шаблон:Gli macromolecules, creating Шаблон:Gli between them, and protecting specimens from decomposition by bacteria and fungi.
2. (population genetics) The process by which a single Шаблон:Gli for a particular Шаблон:Gli with multiple different alleles increases in Шаблон:Gli in a given population such that it becomes permanently established as the only allele at that Шаблон:Gli within the population's Шаблон:Gli.
Any chemical compound or solution that causes the Шаблон:Gli of cells, tissues, or other microscopic structures by any mechanism, thus preserving them for long-term, detailed study by methods such as embedding, Шаблон:Gli, and microscopy. Common fixatives include dilute solutions of ethanol, acetic acid, formaldehyde, and osmium tetroxide, among others.[10]
A long, thin, hair-like appendage protruding from the surface of some cells, which serves locomotory functions by undulating in a way that propels the cell through its environment or by effecting the movement of Шаблон:Gli and solutes past the cell surface. Many unicellular organisms, including some bacteria, protozoa, and algae, bear one or more flagella, and certain cell types in multicellular organisms, namely sperm cells, also have flagella. Eukaryotic flagella are essentially just longer versions of Шаблон:Gli, often up to 150 micrometres (μm) in length, while bacterial flagella are typically smaller and completely different in structure and mechanism of action.[8][10]
The prevailing scientific model of the structure and properties of Шаблон:Gli, according to which the typical membrane consists of Шаблон:Gli of amphipathic Шаблон:Gli (generally Шаблон:Gli or Шаблон:Gli) interspersed with a dynamic variety of embedded Шаблон:Gli, Шаблон:Gli, and (especially in animal cells) Шаблон:Gli, all of which behave as if suspended in a "two-dimensional liquid", constantly moving laterally between the lipids and interacting with each other and with the Шаблон:Gli and the Шаблон:Gli. The membrane as a whole thus retains a fluidity and elasticity which allow it to change shape and adapt to the cell's environment.[24]
An experimental approach in Шаблон:Gli in which a researcher starts with a specific known Шаблон:Gli and attempts to determine the genetic basis of that phenotype by any of a variety of laboratory techniques, commonly by Шаблон:Gli random Шаблон:Gli in the organism's genome and then Шаблон:Gli for changes in the phenotype of interest. Observed phenotypic changes are assumed to have resulted from the mutation(s) present in the screened sample, which can then be Шаблон:Gli to specific genomic Шаблон:Gli and ultimately to one or more specific Шаблон:Gli. This methodology contrasts with Шаблон:Gli, in which a specific gene or its gene product is individually manipulated in order to identify the gene's function.
A type of Шаблон:Gli in a Шаблон:Gli caused by the Шаблон:Gli or Шаблон:Gli of a number of Шаблон:Gli that is not divisible by three. Because of the triplet nature by which nucleotides code for amino acids, a mutation of this sort causes a shift in the Шаблон:Gli of the nucleotide sequence, resulting in the sequence of Шаблон:Gli downstream of the mutation site being completely different from the original.
An organization that works with others "to develop standards for biological research data quality, annotation and exchange" as well as software tools that facilitate their use.[25]
A technique used in Шаблон:Gli to produce a visible Шаблон:Gli by staining the condensed chromosomes with Giemsa stain. The staining produces consistent and identifiable patterns of dark and light "bands" in regions of Шаблон:Gli, which allows specific chromosomes to be easily distinguished.
A Шаблон:Gli cell that is the Шаблон:Gli product of a progenitor Шаблон:Gli and the final product of the Шаблон:Gli in sexually reproducing multicellular organisms. Gametes are the means by which an organism passes its genetic information to its offspring; during fertilization, two gametes (one from each parent) are fused into a single Шаблон:GliШаблон:Gli.
Any segment or set of segments of a Шаблон:Gli molecule that contains the information necessary to produce a functional Шаблон:Gli transcript in a controlled manner. In living organisms, genes are often considered the fundamental units of Шаблон:Gli and are typically encoded in Шаблон:Gli. A particular gene can have multiple different versions, or Шаблон:Gli, and a single gene can result in a Шаблон:Gli that influences many different Шаблон:Gli.
The number of copies of a particular Шаблон:Gli present in a Шаблон:Gli. Gene dosage directly influences the amount of Шаблон:Gli a cell is able to express, though a variety of controls have evolved which tightly Шаблон:GliШаблон:Gli. Changes in gene dosage caused by mutations include Шаблон:Gli.
The set of processes by which the information encoded in a Шаблон:Gli is used in the synthesis of a Шаблон:Gli, such as a protein or a Шаблон:Gli, or otherwise made available to influence one or more Шаблон:Gli; both the product and the gene encoding it are then said to be expressed. Canonically, the first step is Шаблон:Gli, which produces a Шаблон:Gli molecule complementary to the Шаблон:Gli molecule in which the gene is encoded. For protein-coding genes, the second step is Шаблон:Gli, in which the messenger RNA is read by a Шаблон:Gli to produce a Шаблон:Gli and ultimately a protein. The information contained within a DNA sequence need not necessarily be transcribed and translated to exert an influence on molecular events, however: broader definitions encompass a huge variety of other ways in which genetic information can be expressed.
In the typical model of Шаблон:Gli, genetic information (red) encoded in a DNA molecule is Шаблон:Gli with help from nearby Шаблон:Gli into a raw Шаблон:Gli, then processed into a mature form by the removal of Шаблон:Gli and the addition of a Шаблон:Gli and a Шаблон:Gli, then finally Шаблон:Gli into a polypeptide sequence which is folded into a functional protein.
The union, either by natural mutation or by Шаблон:Gli laboratory techniques, of two or more previously independent genes that code for different gene products such that they become subject to control by the same Шаблон:Gli systems. The resulting hybrid sequence is known as a Шаблон:Gli.[6]
Any of a variety of methods used to precisely identify the Шаблон:Gli of a particular Шаблон:Gli within a DNA molecule (such as a chromosome) and/or the physical or Шаблон:Gli distances between it and other genes.
Any of the biochemical material resulting from the Шаблон:Gli of a Шаблон:Gli, most commonly interpreted as the functional Шаблон:Gli produced by Шаблон:Gli of the gene or the fully constructed Шаблон:Gli produced by Шаблон:Gli of the transcript, though Шаблон:Gli molecules such as Шаблон:Gli may also be considered gene products. A measurement of the quantity of a given gene product that is detectable in a cell or tissue is sometimes used to infer how active the corresponding gene is.
The broad range of mechanisms used by cells to control the activity of their genes, especially to allow, prohibit, increase, or decrease the production or Шаблон:Gli of specific Шаблон:Gli, such as Шаблон:Gli or Шаблон:Gli. Gene regulation increases an organism's versatility and adaptability by allowing its cells to express different gene products when required by changes in its environment. In multicellular organisms, the regulation of gene expression also drives Шаблон:Gli and Шаблон:Gli in the Шаблон:Gli, enabling the creation of a diverse array of Шаблон:Gli from the same Шаблон:Gli.
Any mechanism of Шаблон:Gli which drastically reduces or completely prevents the Шаблон:Gli of a particular gene. Gene silencing may occur naturally during either Шаблон:Gli or Шаблон:Gli. Laboratory techniques often exploit natural silencing mechanisms to achieve Шаблон:Gli.
The insertion of a functional or Шаблон:Gli gene or part of a gene into an organism (especially a patient) with the intention of correcting a Шаблон:Gli, either by direct substitution of the defective gene or by supplementation with a second, functional version.[15]
A Шаблон:Gli technology used to simultaneously inactivate, identify, and report the Шаблон:Gli of a target gene in a mammalian genome by introducing an insertional Шаблон:Gli consisting of a Шаблон:GliШаблон:Gli gene and/or a Шаблон:Gli flanked by an upstream Шаблон:Gli site and a downstream Шаблон:Gli termination sequence.
1. In any given organism, a single reproductive cycle, or the phase between two consecutive reproductive events, i.e. between an individual organism's reproduction and that of the progeny of that reproduction; or the actual or average length of time required to complete a single reproductive cycle, either for a particular Шаблон:Gli or for a population or species as a whole.
2. In a given population, those individuals (often but not necessarily living contemporaneously) who are equally removed from a given Шаблон:Gli by virtue of the same number of reproductive events having occurred between them and the ancestor.[15]
Any illness, disease, or other health problem directly caused by one or more abnormalities in an organism's Шаблон:Gli which are congenital (present at birth) and not acquired later in life. Causes may include a Шаблон:Gli to one or more Шаблон:Gli, or a Шаблон:Gli such as an Шаблон:Gli of a particular chromosome. The mutation responsible Шаблон:Gli during embryonic development or may be Шаблон:Gli from one or both parents, in which case the genetic disorder is also classified as a Шаблон:Gli. Though the abnormality itself is present before birth, the actual disease it causes may not develop until much later in life; some genetic disorders do not necessarily guarantee eventual disease but simply Шаблон:Gli of developing it.
A measure of the genetic divergence between species, populations within a species, or individuals, used especially in Шаблон:Gli to express either the time elapsed since the existence of a Шаблон:Gli or the degree of differentiation in the Шаблон:Gli comprising the Шаблон:Gli of each population or individual.
The direct, deliberate manipulation of an organism's genetic material using any of a variety of biotechnology methods, including the Шаблон:Gli or Шаблон:Gli of Шаблон:Gli, the transfer of genes within and between species, the Шаблон:Gli of existing sequences, and the construction of novel sequences using Шаблон:Gli. Genetic engineering encompasses a broad set of technologies by which the genetic composition of individual cells, tissues, or entire organisms may be altered for various purposes, commonly in order to study the functions and Шаблон:Gli of individual genes, to produce hormones, vaccines, and other drugs, and to create Шаблон:Gli for use in research and agriculture.
A specific, easily identifiable, and usually highly Шаблон:GliШаблон:Gli or other Шаблон:GliШаблон:Gli with a known location on a Шаблон:Gli that can be used to identify the individual or species possessing it.
Any reassortment or exchange of genetic material within an individual organism or between individuals of the same or different species, especially that which creates Шаблон:Gli. In the broadest sense, the term encompasses a diverse class of naturally occurring mechanisms by which Шаблон:Gli are copied or physically transferred into different genetic environments, including Шаблон:Gli during Шаблон:Gli or Шаблон:Gli or as a normal part of Шаблон:Gli; Шаблон:Gli events such as Шаблон:Gli, Шаблон:Gli, or Шаблон:Gli; or errors in Шаблон:Gli or cell division. Artificial recombination is central to many Шаблон:Gli techniques which produce Шаблон:Gli.
The redundant encoding of two or more distinct Шаблон:Gli that ultimately perform the same biochemical function. Шаблон:Gli in one of these genes may have a smaller effect on fitness than might be expected, since the redundant genes often compensate for any Шаблон:Gli and obviate any Шаблон:Gli.
A graph that represents the regulatory complexity of Шаблон:Gli. The vertices (nodes) are represented by various regulatory elements and Шаблон:Gli while the edges (links) are represented by their interactions. These network structures also represent functional relationships by approximating the rate at which genes are Шаблон:Gli.
A broad class of various procedures used to identify features of an individual's particular chromosomes, genes, or proteins in order to determine parentage or ancestry, diagnose vulnerabilities to heritable diseases, or detect Шаблон:Gli alleles associated with increased risks of developing Шаблон:Gli. Genetic testing is widely used in human medicine, agriculture, and biological research.
Any organism whose genetic material has been altered using Шаблон:Gli techniques, particularly in a way that does not occur naturally by mating or by natural Шаблон:Gli.
1. The entire complement of genetic material contained within the Шаблон:Gli of an organism, Шаблон:Gli, or virus.
2. The collective set of Шаблон:Gli or genetic Шаблон:Gli shared by every member of a population or species, regardless of the different Шаблон:Gli that may be present at these loci in different individuals.
A method of Шаблон:Gli in which the Шаблон:Gli of Шаблон:Gli fragments in a Шаблон:Gli are assembled into a longer sequence, such as that of a full chromosome or the entire genome, by placing fragments with overlapping ends, known as Шаблон:Gli, adjacent to each other. By repeating this procedure, one can hypothetically determine the correct arrangement of contigs for the entire sequence.[3]
An Шаблон:Gli phenomenon that causes Шаблон:Gli to be Шаблон:Gli in a manner dependent upon the particular parent from which the gene was inherited. It occurs when epigenetic marks such as Шаблон:Gli or Шаблон:Gli are established or "imprinted" in the Шаблон:Gli of a parent organism and subsequently maintained through cell divisions in the Шаблон:Gli of the organism's progeny; as a result, a gene in the progeny that was inherited from the father may be expressed differently than another copy of the same gene that was inherited from the mother.
A region of a Шаблон:Gli that shows evidence of Шаблон:Gli from another organism. The term is used especially in describing microbial genomes such as those of bacteria, where genomic islands having the same or similar sequences commonly occur in species or strains that are otherwise only distantly related, implying that they were not passed on through vertical descent from a common ancestor but through some form of lateral transfer such as Шаблон:Gli. These islands often contain functional genes which confer adaptive traits such as Шаблон:Gli.
An interdisciplinary field that studies the structure, function, evolution, mapping, and editing of entire Шаблон:Gli, as opposed to individual Шаблон:Gli.
The ability of certain chemical agents to cause damage to genetic material within a living cell (e.g. through single- or double-stranded breaks, Шаблон:Gli, or Шаблон:Gli), which may or may not result in a permanent Шаблон:Gli. Though all Шаблон:Gli are genotoxic, not all genotoxic compounds are mutagenic.
The process of determining differences in the Шаблон:Gli of an individual by examining the Шаблон:Gli in the individual's Шаблон:Gli using Шаблон:Gli and comparing them to another individual's sequences or a reference sequence.
Any Шаблон:Gli that gives rise to the Шаблон:Gli of a sexually reproducing organism. Germ cells are the vessels for the genetic material which will ultimately be passed on to the organism's descendants and are usually distinguished from Шаблон:Gli, which are entirely separate from the Шаблон:Gli.
1. In multicellular organisms, the subpopulation of cells which are capable of passing on their genetic material to the organism's progeny and are therefore (at least theoretically) distinct from Шаблон:Gli, which cannot pass on their genetic material except to their own immediate Шаблон:Gli daughter cells. Cells of the germ line are called Шаблон:Gli.
2. The Шаблон:Gli of germ cells, spanning many generations, that contains the genetic material which has been passed on to an individual from its ancestors.
The chain of Шаблон:Gli reactions that results in the generation of Шаблон:Gli from some non-carbohydrate carbon substrates, including the Шаблон:Gli. It is one of two primary Шаблон:Gli used by most animals to maintain blood sugar levels (the other being Шаблон:Gli), especially during periods of fasting, starvation, and intense exercise.
A simple sugar with the molecular formula Шаблон:Chem and the most abundant Шаблон:Gli in nature, being the primary product of photosynthesis, where it is made in a sunlight-powered reaction of water with carbon dioxide. All living organisms are capable of metabolizing glucose via Шаблон:Gli, an exergonic pathway which for most organisms is the primary means of obtaining chemical energy to power cellular activities.[10] Metabolic glucose is usually stored in the form of large polymeric aggregates such as amylose in plants and Шаблон:Gli in animals, and is released by the breakdown of these polymers via Шаблон:Gli.
A branched Шаблон:Gli composed of as many as 30,000 covalently bonded units of the Шаблон:GliШаблон:Gli which functions as the primary form of short-term energy storage in most animal cells.[10][4] Glycogen reserves are especially abundant in muscle and liver cells,[8] where they can be metabolized at-need into their component glucoses as a means of buffering blood sugar levels, a process known as Шаблон:Gli.
A Шаблон:Gli in which polymeric Шаблон:Gli molecules are broken down into individual Шаблон:Gli monomers by the sequential removal of glucose units via phosphorolysis, a reaction catalyzed by the enzyme glycogen phosphorylase. Glycogenolysis is one of two primary pathways used in animal tissues to generate free glucose for the maintenance of blood sugar levels, the other being Шаблон:Gli.
The Шаблон:Gli in which Шаблон:Gli sugars such as Шаблон:Gli are broken down into simpler molecules, releasing chemical energy which can then be used for various cellular functions. In a series of ten enzyme-catalyzed reactions, each molecule of glucose is converted into two molecules of Шаблон:Gli, with the free energy liberated in this process simultaneously being used to form high-energy bonds in two molecules of reduced Шаблон:Gli (NADH) and two molecules of Шаблон:Gli (ATP). In Шаблон:Gli conditions pyruvate and NADH are further oxidized in the Шаблон:Gli; in Шаблон:Gli conditions NADH itself subsequently reduces pyruvate to lactate.
Шаблон:Gli converts Шаблон:Gli to Шаблон:Gli via a series of 10 steps, each catalyzed by a different enzyme and producing different intermediate metabolites. Steps 1 and 3 consume Шаблон:Gli (blue arrows) and steps 7 and 10 produce ATP (yellow arrows); steps 6 through 10 occur twice per molecule of glucose.
A Шаблон:Gli with one or more Шаблон:Gli molecules, typically short Шаблон:Gli chains, covalently attached to one or more of its amino acid side chains.[8] Proteins exposed on the outer surface of the Шаблон:Gli or secreted into the extracellular space are commonly modified in this way, after which they are said to be Шаблон:Gli.
Any chemical compound consisting of a Шаблон:Gli molecule covalently bonded to another molecule containing a hydroxyl group (including other carbohydrates) via one or more Шаблон:ChemШаблон:Gli. When all of the compound's substituents are carbohydrates, the glycoside is a Шаблон:Gli.[10]
A covalent ether bond that connects a carbon atom within a Шаблон:Gli molecule (e.g. a Шаблон:Gli) or a carbohydrate derivative to another substituent or functional group, which may or may not be another carbohydrate; such bonds form as the result of a dehydration reaction between hydroxyl groups on each molecule. A substance containing a glycosidic bond is known as a Шаблон:Gli.
The attachment of a carbohydrate molecule (e.g. Шаблон:Gli) to an amino acid residue within a Шаблон:Gli or Шаблон:Gli by covalent bonding, a process which takes place in or near the Шаблон:Gli.[10]
The proportion of Шаблон:Gli in a Шаблон:Gli that are either Шаблон:Gli (Шаблон:Font) or Шаблон:Gli (Шаблон:Font), typically expressed as a percentage. DNA and RNA molecules with higher GC-content are generally more thermostable than those with lower GC-content due to molecular interactions that occur during base stacking.[28]
A short Шаблон:GliШаблон:Gli which complexes with Cas Шаблон:Gli and, by annealing to a specific complementary sequence in a Шаблон:Gli molecule, serves to "guide" these proteins to viral DNA introduced by foreign pathogens, which can then be digested and degraded as part of an adaptive immune defense employed by bacteria and archaea. Custom-made guide RNAs are designed by scientists to target specific genomic loci in CRISPR-Cas Шаблон:Gli.
A characteristic Шаблон:Gli that commonly forms in self-complementary Шаблон:Gli by intramolecular Шаблон:Gli between different parts of the same linear, Шаблон:Gli molecule. The resulting conformation resembles a hairpin, where non-adjacent lengths of nucleotides form hydrogen bonds with each other, creating a local double-stranded Шаблон:Gli (the "stem") which ends in a circle of unpaired nucleotides (the "loop"). Hairpin loops form readily in single-stranded DNA molecules containing Шаблон:Gli[3] and are especially common in large RNA molecules, where they play various roles in promoting or inhibiting the formation of other secondary structures, stabilizing Шаблон:Gli, providing recognition sites for Шаблон:Gli, or serving as Шаблон:Gli for enzymes.[29]
The structure of a basic Шаблон:Gli in a single-stranded RNA molecule
In a Шаблон:Gli organism, having just one Шаблон:Gli at a given Шаблон:Gli (where there would ordinarily be two). Hemizygosity may be observed when only one copy of a Шаблон:Gli is present in a normally diploid cell or organism, or when a segment of a chromosome containing one copy of an allele is Шаблон:Gli, or when a gene is located on a Шаблон:Gli in the heterogametic sex (in which the sex chromosomes do not exist in matching pairs); for example, in human males with normal chromosomes, almost all Шаблон:Gli genes are said to be hemizygous because there is only one Шаблон:Gli and few of the same genes exist on the Шаблон:Gli.
The storage, transfer, and expression of molecular information in biological organisms,[15] as manifested by the passing on of Шаблон:Gli from parents to their Шаблон:Gli, either through sexual or asexual reproduction. Offspring cells or organisms are said to inherit the genetic information of their parents.
A compact, highly condensed form of Шаблон:Gli characterized chiefly by the close spatial proximity of adjacent Шаблон:Gli and the consequent inaccessibility of intervening DNA sequences to Шаблон:Gli, which contrasts with the more open and accessible form known as Шаблон:Gli. The transcription of genes located within heterochromatic regions of chromosomes is therefore relatively limited, and so the formation of heterochromatin at specific loci is an important means of regulating Шаблон:Gli. Establishment of heterochromatin is associated with the Шаблон:Gli of specific residues within specific Шаблон:Gli, such as Шаблон:Gli of the ninth lysine residue of histone H3 (H3K9); the presence of these modifications at a specific locus signals the recruitment of other proteins which cause local DNA condensation. Many repetitive and structurally important regions of chromosomes are nearly always compacted in so-called Шаблон:Gli, while the compaction of Шаблон:Gli is more temporary.
The Шаблон:Gli of a foreign Шаблон:Gli or any other foreign DNA sequence within a host organism which does not naturally contain the same gene. Insertion of foreign Шаблон:Gli into heterologous hosts using Шаблон:GliШаблон:Gli is a common biotechnology method for studying gene structure and function.
Describing a method or system capable of Шаблон:Gli very large numbers of samples or of processing very large quantities of data extremely rapidly, generally by utilizing automation and miniaturization to greatly increase speed and efficiency. For example, high-throughput sequencing refers to modern Шаблон:Gli technologies that can produce sequence reads for hundreds of millions of DNA fragments simultaneously, allowing scientists to Шаблон:Gli quickly and inexpensively.[30]
The study or analysis of the microscopic anatomy of biological Шаблон:Gli or of Шаблон:Gli within tissues, particularly by making use of specialized techniques to distinguish structures and functions based on visual morphology and differential staining. In practice the term is sometimes used more broadly to include Шаблон:Gli.
Any of a class of highly alkalineШаблон:Gli responsible for Шаблон:GliШаблон:Gli DNA into structural units called Шаблон:Gli in eukaryotic cells. Histones are the chief protein components of Шаблон:Gli, where they associate into Шаблон:Gli which act as "spools" around which the linear DNA molecule winds. They play a major role in Шаблон:Gli and Шаблон:Gli.
The complex of eight Шаблон:Gli proteins around which double-stranded DNA wraps within a Шаблон:Gli. The canonical histone octamer consists of two each of histones H2A, H2B, H3, and H4, which pair with each other symmetrically to form a ball-shaped cluster around which DNA winds through interactions with the histones' surface Шаблон:Gli, though Шаблон:Gli may replace their analogues in certain contexts.
The Шаблон:Gli of Шаблон:Gli proteins by the chemical attachment of various molecules or functional groups to specific amino acid residues. Because histones form the Шаблон:Gli of Шаблон:Gli, the modification of exposed parts of their polypeptide chains is used to regulate gene expression by marking them with Шаблон:Gli that signal the recruitment of other proteins to induce conformational changes that variously widen or condense the spacing of nucleosomes along strands of DNA, thereby changing the accessibility of nearby DNA sequences to transcriptional machinery. Histones are modified by many different labels, most commonly Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli.
(of a linear Шаблон:Gli or chromosome fragment) Having no single Шаблон:Gli but rather multiple Шаблон:Gli assembly sites dispersed along the entire length of the chromosome. During cell division, the Шаблон:Gli of holocentric chromosomes move apart in parallel and do not form the classical V-shaped structures typical of Шаблон:Gli chromosomes.
Any of a class of DNA Шаблон:Gli approximately 180 base pairs in length occurring near the Шаблон:Gli of certain eukaryotic genes and encoding a 60-amino acid domain, known as a Шаблон:Gli, which is capable of Шаблон:Gli via a characteristic helix-turn-helix motif. Homeobox-containing genes are translated into homeodomain-containing proteins, which commonly Шаблон:Gli transcription or translation by binding to other genes or messenger RNAs containing Шаблон:Gli. The products of many homeotic genes, exemplified by the Шаблон:Gli, are of critical importance in developmental pathways.[6]
A Шаблон:Gli, typically 60 Шаблон:Gli in length, found near the Шаблон:Gli of certain eukaryotic Шаблон:Gli, characterized by a highly Шаблон:Gli helix-turn-helix Шаблон:Gli that binds with strong affinity to the backbone of specific Шаблон:Gli in DNA or RNA molecules. A protein may have one or more homeodomains, each of which is specific to a different recognition sequence. Many homeodomain-containing proteins function as Шаблон:Gli by binding to sequences within Шаблон:Gli and blocking or recruiting other proteins, such as Шаблон:Gli or Шаблон:Gli of the Шаблон:Gli. Homeodomains are the Шаблон:Gli versions of Шаблон:Gli, though the terms are often used interchangeably.
A set of two matching Шаблон:Gli, one maternal and one paternal, which pair up with each other inside the nucleus during Шаблон:Gli. They have the same Шаблон:Gli at the same Шаблон:Gli, but may have different Шаблон:Gli.
A type of Шаблон:Gli in which nucleotide sequences are exchanged between two similar or identical ("homologous") molecules of Шаблон:Gli, especially that which occurs between Шаблон:Gli. The term may refer to the recombination that occurs as a part of any of a number of distinct cellular processes, most commonly Шаблон:Gli or Шаблон:Gli during Шаблон:Gli in eukaryotes and Шаблон:Gli in prokaryotes. Contrast Шаблон:Gli.
Any process by which genetic material is transferred between unicellular and/or multicellular organisms other than by vertical transmission from parent to offspring, e.g. bacterial conjugation.
Any Шаблон:Gli that is Шаблон:Gli at a relatively constant level across many or all known conditions and cell types. The Шаблон:Gli of housekeeping genes typically play critical roles in the maintenance of cellular integrity and basic metabolic function. It is generally assumed that their expression is unaffected by experimental or pathological conditions.
A subset of highly Шаблон:GliШаблон:Gli-containing Шаблон:Gli whose protein products function as Шаблон:Gli essential for the proper organization of the body plan in developing animal Шаблон:Gli, ensuring that the correct structures are formed in the correct places. Hox genes are usually arranged on a chromosome in Шаблон:Gli arrays and are Шаблон:Gli sequentially during development, with the sequence of gene activation corresponding to their physical arrangement within the genome and/or the physical layout of the tissues in which they are expressed along the organism's anterior–posterior axis.[6]
A collaborative international scientific research project with the goal of Шаблон:Gli all of the Шаблон:Gli and identifying and Шаблон:Gli all of the Шаблон:Gli within human cells, and ultimately of assembling a complete Шаблон:Gli for the human species. The project was launched in 1990 by a consortium of federal agencies, universities, and research institutions and was declared complete in 2003. Because each individual human being has a unique genome, the finished reference genome is a Шаблон:Gli of sequences obtained by sampling DNA from thousands of individuals across the world and does not represent any one individual.
The Шаблон:Gli that results from combining the qualities of two organisms of different genera, species, breeds, or varieties through sexual reproduction. Hybrids may occur naturally or artificially, as during Шаблон:Gli of domesticated animals and plants. Reproductive barriers typically prevent hybridization between distantly related organisms, or at least ensure that hybrid offspring are sterile, but fertile hybrids may result in speciation.
1. The process by which a Шаблон:Gli organism is produced from two organisms of different genera, species, breeds, or varieties.
2. The process by which two or more Шаблон:GliШаблон:Gli molecules with Шаблон:Gli nucleotide sequences Шаблон:Gli with each other in solution, creating Шаблон:Gli or Шаблон:Gli molecules via the formation of hydrogen bonds between the complementary nucleobases of each strand. In certain laboratory contexts, especially ones in which long strands hybridize with short Шаблон:GliШаблон:Gli, hybridization is often referred to as Шаблон:Gli.
3. A step in some experimental assays in which a single-stranded DNA or RNA preparation is added to an array surface and anneals to a Шаблон:GliШаблон:Gli.
A Шаблон:GliШаблон:Gli or Шаблон:Gli fragment (or a Шаблон:Gli) which is artificially Шаблон:Gli with a radioactive or fluorescent compound or some other detectable marker and then allowed to Шаблон:Gli with Шаблон:Gli DNA or RNA sequences in order to detect the presence of those complements in a heterogeneous sample or their specific Шаблон:GliШаблон:Gli; or an Шаблон:Gli in which this procedure is performed. As with antibodies in Шаблон:Gli, nucleic acid probes bind with high specificity to their target sequences, permitting visualization of the targets, if present, against a non-specific background, whether in a Шаблон:Gli or Шаблон:Gli or even Шаблон:Gli. A unique advantage of hybridization probes is that the Шаблон:Gli of the hybridization reaction is easily modifiable by changing the temperature and salt concentration, making it possible for the same probe to bind to sequences with differing degrees of complementarity. Hybridization probes are employed in Шаблон:Gli and Шаблон:Gli and as part of many other laboratory methods. See also Шаблон:Gli.
Soluble in or having an affinity for water or other polar compounds; describing a polar molecule, or a moiety or functional group within a molecule, which participates in intermolecular interactions such as hydrogen bonding with other polar molecules and therefore readily dissolves in polar solvents such as water or aqueous solutions.[8] Unlike Шаблон:Gli compounds, hydrophilic compounds can form energetically favorable contacts with the aqueous phase of biological fluids and so can often be suspended directly in the Шаблон:Gli or exposed to extracellular spaces.[4] Together, the contrasting properties of hydrophilicity and hydrophobicity play major roles in determining the structural Шаблон:Gli and functions of most Шаблон:Gli.
Having a low solubility in or affinity for water or other polar solvents; describing a non-polar molecule, or a moiety or functional group within a molecule, which cannot form energetically favorable interactions with polar compounds and which therefore tends to "avoid" or be repulsed by such compounds, instead clustering together with other hydrophobic molecules or arranging itself in a way that minimizes its exposure to its polar surroundings. This phenomenon is not so much due to the affinity of the hydrophobic molecules for each other as it is a consequence of the strong intermolecular forces that allow polar compounds such as water molecules to bond with each other; hydrophobic species are unable to form alternative bonds of equivalent strength with the polar compounds, hence they tend to be excluded from aqueous solutions by the tendency of the polar solvent to maximize interactions with itself. Hydrophobicity is a major determinant of countless chemical interactions in biological systems, including the spatial Шаблон:Gli assumed by Шаблон:Gli such as Шаблон:Gli and Шаблон:Gli, the binding of Шаблон:Gli and Шаблон:Gli to proteins, and the structure and properties of lipid Шаблон:Gli.[10][8] Contrast Шаблон:Gli.
Describing a solution containing a high concentration of dissolved solutes relative to another solution, i.e. having positive osmotic pressure, such that solvent will tend to move by osmosis across a semipermeable membrane from the solution of lower solute concentration to the solution of higher concentration until both solutions have equal concentrations. In a cell where the intracellular Шаблон:Gli is hypertonic relative to the surrounding Шаблон:Gli (which by definition is Шаблон:Gli relative to the cytosol), the solvent (water) will flow across the Шаблон:Gli into the cytosol, filling the cell with extra water and diluting its contents until both sides of the membrane are Шаблон:Gli. Cells placed in severely hypotonic environments may be at risk of bursting due to the sudden inflow.
A mutant Шаблон:Gli that permits a subnormal expression of the gene's normal phenotype, e.g. by encoding an unstable enzyme which degrades too quickly to fully serve its function but which nevertheless is functional in some limited capacity, being generated in quantities sufficient for its reaction to proceed slowly or at low levels.[6]
Describing a solution containing a low concentration of dissolved solutes relative to another solution, i.e. having negative osmotic pressure, such that solvent will tend to move by osmosis across a semipermeable membrane from the solution of lower solute concentration to the solution of higher concentration until both solutions have equal concentrations. In a cell where the intracellular Шаблон:Gli is hypotonic relative to the surrounding Шаблон:Gli (which by definition is Шаблон:Gli relative to the cytosol), the solvent (water) will flow across the Шаблон:Gli out of the cytosol, causing the cell to lose water until both sides of the membrane are Шаблон:Gli. Cells placed in severely hypertonic environments may be at risk of shriveling and desiccating due to the sudden outflow.
A naturally occurring non-canonical Шаблон:GliШаблон:Gli that is used in some Шаблон:Gli molecules and pairs with standard nucleobases in a phenomenon known as Шаблон:Gli. Its Шаблон:Gli form is known as Шаблон:Gli, which is the reason it is commonly abbreviated with the letter Шаблон:Font in sequence reads.
A diagrammatic or schematic Шаблон:Gli of the entire set of Шаблон:Gli within a cell or genome, in which annotated illustrations depict each chromosome in its most idealized form (e.g. with straight lines and obvious Шаблон:Gli) so as to facilitate the easy identification of sequences, structural features, and physical distances, which may be less apparent in photomicrographs of the actual chromosomes.
The natural or artificial changing of a Шаблон:Gli with a normally finite lifespan into one with a hypothetically infinite lifespan, capable of dividing indefinitely without Шаблон:Gli as long as essential nutrients are available and conditions are conducive for Шаблон:Gli. Cells that undergo such a change are said to be immortalized. Mutations that cause immortalization occur naturally in the Шаблон:Gli that cause cancer but can also be induced artificially, which makes it possible to Шаблон:Gli certain cell lines Шаблон:Gli for prolonged periods. Immortalized cell lines are thus broadly useful for experimental purposes and in many biotechnology applications. Immortalized eukaryotic cells are commonly obtained by isolating them from a naturally occurring neoplasm (as with the human HeLa cell line), or may be generated from normal cells by introducing viral genes (as with HEK 293 cells), by artificially Шаблон:Gli proteins required for immortality such as Шаблон:Gli, or by Шаблон:Gli normal cells with cancer cells (as in the Шаблон:Gli technologies used in the commercial production of Шаблон:Gli).[3] Though Шаблон:Gli are also capable of continuous self-renewal and are thus technically 'immortal', their immortalization is not abnormal because they are an ordinary part of the development of multicellular organisms.
A family of laboratory techniques in which a particular Шаблон:Gli or Шаблон:Gli is conjugated to a fluorescent dye and then allowed to bind specifically to its complementary antibody or antigen, if any exists, in a Шаблон:Gli, tissue section or smear, Шаблон:Gli, membrane Шаблон:Gli, or any other context. The presence or absence of the complement and its specific location(s) can be visualized by illuminating the sample with ultraviolet light and observing the fluorescence from the conjugated fluorophore, often under a microscope.[3]
The use of an Шаблон:GliШаблон:Gli to a Шаблон:Gli or Шаблон:Gli to bind a specific Шаблон:Gli within a target substance (e.g. a protein) and thereby make the substance visible amidst a background of non-specific substances, allowing for detection of the target in a biological sample. The term originally referred to antibody-based staining of tissue sections with strong dyes or colorants, known as Шаблон:Gli, but in modern usage encompasses a much broader range of laboratory methods united by their use of antibodies to Шаблон:Gli specific biomolecules with visually conspicuous compounds.
(of a scientific experiment or research) Conducted, produced, or analyzed by means of computer modeling or simulation, as opposed to a real-world trial.
(of a scientific experiment or biological process) Occurring or made to occur in a natural, uncontrolled setting, or in the natural or original position or place, as opposed to in a foreign cell or tissue type or Шаблон:Gli.
A Шаблон:Gli assay in which a Шаблон:Gli, single-stranded DNA or RNA molecule or Шаблон:Gli containing a sequence that is Шаблон:Gli to a particular DNA or RNA sequence is allowed to Шаблон:Gli with its complement Шаблон:Gli, i.e. in its natural context, such as within cells or tissue sections (as opposed to within homogeneous samples extracted from cells or tissues, where cellular or histological structure has been lost in the process of obtaining the sample), in order to Шаблон:Gli of the complementary sequence within this context. The label may be a radioactive compound, Шаблон:Gli, or Шаблон:Gli, permitting detection by a variety of visualization techniques. In situ hybridization is commonly used to identify the physical locations of specific DNA sequences such as genes and regulatory elements on Шаблон:Gli, which can provide insight into chromosomal structure and integrity; to determine the subcellular locations where various types of RNA accumulate and interact with other molecules; and to visualize the tissues and organs within an organism where specific genes are Шаблон:Gli at various developmental stages (by probing for the genes' RNA transcripts).
(of a scientific experiment or biological process) Occurring or made to occur in a laboratory vessel or other controlled artificial environment, e.g. in a test tube or a petri dish, as opposed to Шаблон:Gli or Шаблон:Gli.
(of a scientific experiment or biological process) Occurring or made to occur inside the cells or tissues of a living organism; or, in the broadest sense, in any natural, unmanipulated setting. Contrast Шаблон:Gli and Шаблон:Gli.
1. (of a gene or sequence) Read or transcribed in the same Шаблон:Gli as another gene or sequence; not requiring a shift in reading frame to be intelligible or to result in a functional Шаблон:Gli.
Any nucleotide sequence that is Шаблон:Gli naturally or artificially into another sequence. The term is used in particular to refer to the part of a Шаблон:Gli that codes for those proteins directly involved in the transposition process, e.g. the Шаблон:Gli enzyme. The coding region in a transposable insertion sequence is usually flanked by short Шаблон:Gli, and the structure of larger transposable elements may include a pair of flanking insertion sequences which are themselves inverted.
The alteration of a DNA sequence by the Шаблон:Gli of one or more nucleotides into the sequence, either naturally or artificially. Depending on the precise location of the insertion within the target sequence, insertions may partially or totally inactivate or even upregulate a Шаблон:Gli or biochemical pathway, or they may be Шаблон:Gli, leading to no substantive changes at all. Many Шаблон:Gli techniques rely on the insertion of exogenous genetic material into host cells in order to study gene function and expression.[6]
Any of a class of Шаблон:Gli which are permanently embedded within or attached to the Шаблон:Gli (as opposed to those which are Шаблон:Gli). Integral membrane proteins can be subclassified into Шаблон:Gli, which span the entirety of the membrane, and Шаблон:Gli, which adhere only to one side.
Any of a class of Шаблон:Gli which are permanently attached to one side of the Шаблон:Gli by any means but which do not completely span the membrane. Contrast Шаблон:Gli.
Any of a class of Шаблон:Gli which span the entirety of the Шаблон:Gli, extending from the interior or Шаблон:Gli side of the membrane to the exterior or Шаблон:Gli side. Transmembrane proteins typically have hydrophilic Шаблон:Gli exposed to each side as well as one or more hydrophobic domains crossing the nonpolar space inside the Шаблон:Gli, by which they are further classified as single-pass or multipass membrane proteins. As such many transmembrane proteins function as Шаблон:Gli or Шаблон:Gli to permit or prohibit the movement of specific molecules or ions across the membrane, often undergoing conformational changes in the process, or as Шаблон:Gli in Шаблон:Gli pathways. Contrast Шаблон:Gli.
A Шаблон:Gli consisting of a Шаблон:Gli containing the gene for a Шаблон:Gli, Шаблон:Gli-specific recognition sites, and a Шаблон:Gli that governs the expression of one or more genes conferring adaptive traits on the host cell. Integrons usually exist in the form of circular Шаблон:Gli DNA fragments, through which they facilitate the rapid adaptation of bacteria by enabling Шаблон:Gli of antibiotic resistance genes between different bacterial species.[6]
The insertion, naturally or artificially, of chemical compounds between the planar Шаблон:Gli of a Шаблон:Gli molecule, which generally disrupts the hydrogen bonding necessary for Шаблон:Gli.
Two molecules of the chemotherapeutic drug doxorubicinШаблон:Gli between the bases of a DNA molecule
The abbreviated pause in activities related to cell division that occurs during Шаблон:Gli in some species, between the first and second meiotic divisions (i.e. meiosis I and meiosis II). No Шаблон:Gli occurs during interkinesis, unlike during the normal Шаблон:Gli that precedes meiosis I and Шаблон:Gli.[6]
A sequence present in some Шаблон:Gli that permits recognition by the Шаблон:Gli and thus the initiation of Шаблон:Gli even in the absence of a Шаблон:Gli, which in eukaryotes is otherwise required for assembly of the initiation complex. IRES elements are often located in the Шаблон:Gli, but may also be found in other positions.
An international non-governmental organization devoted to promoting scientific research and education in the disciplines of Шаблон:Gli and Шаблон:Gli, primarily by standardizing biochemical nomenclature, developing and publishing laboratory methods, and awarding grants and fellowships to students and researchers.
All stages of the Шаблон:Gli excluding Шаблон:Gli. A typical cell spends most of its life in interphase, during which it conducts everyday Шаблон:Gli as well as the complete Шаблон:Gli of its genome in preparation for Шаблон:Gli or Шаблон:Gli.
A Шаблон:Gli (or a region or Шаблон:Gli within a protein) that lacks any distinct, fixed three-dimensional structure or organization under physiological conditions, instead changing continuously and randomly between multiple transient Шаблон:Gli rather than folding into any one stable conformation, especially in the absence of specific macromolecular interaction partners. The majority of eukaryotic proteins contain domains with intrinsic structure alongside unstructured domains. Шаблон:Gli lacking intrinsic order are generally characterized by high proportions of charged and hydrophilic amino acids and low proportions of hydrophobic amino acids, making them inherently flexible, accessible, and modifiable, which allows the same peptide sequence to have distinct functions across a wide variety of biochemical circumstances. They are frequently enriched in Шаблон:Gli and are common targets of Шаблон:Gli, giving them important roles in Шаблон:Gli pathways and as hubs in Шаблон:Gli.[31]
Any Шаблон:Gli within a functional Шаблон:Gli that is removed by Шаблон:Gli during Шаблон:Gli of the Шаблон:GliШаблон:Gli and is therefore absent from the final mature mRNA. The term refers to both the sequence as it exists within a DNA molecule and to the corresponding sequence in RNA transcripts. Contrast Шаблон:Gli.
The infolding of a Шаблон:Gli toward the interior of a cell or organelle, or of a sheet of cells toward the interior of a developing Шаблон:Gli, Шаблон:Gli, or organ, forming a distinct membrane-lined pocket. In the case of individual cells, the invaginated pocket may proceed to separate from the source membrane entirely, creating a membrane-bound Шаблон:Gli within the cell, as in Шаблон:Gli.[10]
A Шаблон:Gli followed Шаблон:Gli on the same Шаблон:Gli by its own Шаблон:Gli. The initial sequence and the reverse complement may be separated by any number of nucleotides, or may be immediately adjacent to each other; in the latter case, the composite sequence is also called a Шаблон:Gli. Inverted repeats are Шаблон:Gli by definition, a property which involves them in many biological functions and dysfunctions. Contrast Шаблон:Gli.
A type of Шаблон:Gli complex which forms an Шаблон:Gli spanning the Шаблон:Gli of a membrane, through which specific inorganic, electrically charged ions can diffuse down their electrochemical gradients.[8]
Any chemical compound or macromolecule that facilitates the movement of ions across biological membranes, or more specifically, any chemical species that reversibly binds electrically charged atoms or molecules. Many ionophores are lipid-soluble Шаблон:Gli that catalyze the transport of monovalent and divalent cations across the hydrophobic Шаблон:Gli surrounding cells and vesicles.[10]
A large region of Шаблон:Gli with a relatively homogeneous composition of Шаблон:Gli, distinguished from other regions by the proportion of pairs that are Шаблон:Font-Шаблон:Font or Шаблон:Font-Шаблон:Font. The genomes of most plants and vertebrates are composed of different classes of GC-rich and AT-rich isochores.[6]
A type of abnormalШаблон:Gli in which the arms of the chromosome are mirror images of each other. Isochromosome formation is equivalent to simultaneous Шаблон:Gli and Шаблон:Gli events such that two copies of either the Шаблон:Gli or the Шаблон:Gli comprise the resulting chromosome.
The pH at which a particular molecule, often a Шаблон:Gli, carries no net electrical charge, i.e. at which it is electrically neutral in the statistical mean. The concentration of protons (H+) in the surrounding environment affects how readily molecules gain or lose protons and thus their electrical properties. When the environmental pH is greater than the molecule's pI, the molecule is negatively charged, and when the pH is less than the pI, it is positively charged. Isoelectric point is therefore important for determining the behavior of molecules exposed to electric fields, as in Шаблон:Gli and ion chromatography. Proteins are least soluble at their isoelectric points because electrically neutral species do not repulse each other with electrostatic forces, such that they tend to aggregate and precipitate out of solution.[10]
Any of a class of Шаблон:Gli which catalyze the conversion of a molecule from one isomer to another, such that the product of the reaction has the same molecular formula as the original substrate but differs in the connectivity or spatial arrangement of its atoms.
Two or more Шаблон:Gli that are equivalent and redundant in the sense that, despite coding for distinct Шаблон:Gli, they each result in the same Шаблон:Gli when set within the same Шаблон:Gli. If several isomeric genes are present in a single Шаблон:Gli they may be either cumulative or non-cumulative in their contributions to the phenotype.[15]
Describing a solution containing the same concentration of dissolved solutes as another solution, such that the two solutions have equal osmotic pressure. Isotonic solutions separated from each other by a semipermeable membrane (as with a cell, where the intracellular Шаблон:Gli is separated from the Шаблон:Gli by the Шаблон:Gli) have no Шаблон:Gli and thus will not exchange solvent by osmosis. Contrast Шаблон:Gli and Шаблон:Gli.
Any DNA sequence that appears to have no known biological function, or which acts in a way that has no positive or a net negative effect on the fitness of the Шаблон:Gli in which it is located. The term was once more broadly used to refer to all Шаблон:Gli, though much of this was later discovered to have a function; in modern usage it typically refers to broken or vestigial sequences and Шаблон:Gli, including Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, and fragments of Шаблон:Gli and retroviruses, which together constitute a large proportion of the genomes of most eukaryotes. Despite not contributing productively to the host organism, these sequences are able to persist indefinitely inside genomes because the disadvantages of continuing to copy them are too small to be acted upon by Шаблон:Gli.
Any RNA-encoded sequence, especially a Шаблон:Gli, that appears to have no known biological function, or whose function has no positive or a net negative effect on the fitness of the genome from which it is transcribed. Despite remaining Шаблон:Gli, many Шаблон:Gli still serve important functions, whereas junk RNAs are truly useless: often they are the product of accidental transcription of a Шаблон:Gli sequence, or they may result from Шаблон:Gli of Шаблон:Gli, as with Шаблон:GliШаблон:Gli. Junk RNA is usually quickly degraded by Шаблон:Gli and other cytoplasmic enzymes.
A Шаблон:Gli which depicts the entire set of Шаблон:Gli in a cell or organism by using photomicrographs of the actual chromosomes as they appear Шаблон:Gli (usually during Шаблон:Gli, in their most condensed forms), as opposed to the idealized illustrations of chromosomes used in Шаблон:Gli. The photomicrographs are often still arranged in pairs and by size for easier identification of particular chromosomes, whereas in the actual nucleus there is seldom any apparent organization.
The fragmentation and degeneration of the Шаблон:Gli of a dying cell, during which the Шаблон:Gli is destroyed and the contents of the nucleus, including Шаблон:Gli, are dispersed throughout the Шаблон:Gli and degraded by enzymes. Karyorrhexis is usually preceded by Шаблон:Gli and may occur as a result of Шаблон:Gli, Шаблон:Gli, or Шаблон:Gli.
The number and appearance of Шаблон:Gli within the Шаблон:Gli of a eukaryotic cell, especially as depicted in an organized Шаблон:Gli or Шаблон:Gli (in pairs and arranged by size and by position of the Шаблон:Gli). The term is also used to refer to the complete set of chromosomes in a species or individual organism or to any test that detects this complement or measures the chromosome number.
The Шаблон:Gli of a typical human male, as visualized in a karyogram using Шаблон:Gli
The production of Шаблон:Gli via the Шаблон:Gli of Шаблон:Gli or Шаблон:Gli, an exergonic process which is used to supply energy to certain tissues during periods of carbohydrate and protein insufficiency.
Any of a class of Шаблон:Gli which catalyze the transfer of Шаблон:Gli groups from high-energy, phosphate-donating molecules such as Шаблон:Gli to one or more specific Шаблон:Gli, a process known as Шаблон:Gli. The opposite process, known as Шаблон:Gli, is catalyzed by Шаблон:Gli enzymes.
A non-specific, non-directional movement or change in activity by a cell or a population of cells in response to a stimulus, such that the rate of the movement or activity is dependent on the intensity of the stimulus but not on the direction from which the stimulus occurs. Kinesis refers particularly to cellular locomotion without directional bias, in contrast to Шаблон:Gli and Шаблон:Gli.
In Шаблон:Gli, an enlarged, heavily staining Шаблон:Gli that can be used as a visual marker, allowing specific chromosomes to be easily identified in the nucleus.[6]
A Шаблон:Gli method by which the normal rate of Шаблон:Gli of one or more of an organism's Шаблон:Gli is reduced or suppressed (though not necessarily completely turned off, as in Шаблон:Gli), either through direct modification of a DNA sequence or through treatment with a reagent such as a short DNA or RNA Шаблон:Gli with a sequence Шаблон:Gli to either an Шаблон:Gli transcript or a gene.
A Шаблон:Gli method in which one or more novel Шаблон:Gli are Шаблон:Gli into an organism's genome, particularly when targeted to a specific Шаблон:Gli, or in which one or more existing genes are replaced by or Шаблон:Gli with novel genes.[33] This is in contrast to a Шаблон:Gli, in which a gene is deleted or completely inactivated.
A Шаблон:Gli method in which one or more specific Шаблон:Gli are inactivated or entirely Шаблон:Gli an organism's genome, by any of a variety of mechanisms which disrupt their Шаблон:Gli at some point in the pathway that produces their Шаблон:Gli, such that no functional gene products are produced. This allows researchers to study the function of a gene Шаблон:Gli, by observing how the organism's Шаблон:Gli changes when deprived of the gene's normal effects. A complete knockout permanently inactivates the gene; a conditional knockout allows the gene to be turned on or off at will, e.g. at specific times or in specific tissues, by linking the expression of the gene to some easily modifiable biochemical state or condition. In a heterozygous knockout, only one of a diploid organism's two alleles is knocked out; in a homozygous knockout, both copies are knocked out. Contrast Шаблон:Gli.
A highly Шаблон:GliШаблон:GliШаблон:Gli which functions as the recognition site for the initiation of Шаблон:Gli in most eukaryotic Шаблон:Gli, generally a sequence of 10 bases immediately surrounding and inclusive of the Шаблон:Gli: Шаблон:Font. As the Шаблон:Gli scans the transcript, recognition of this sequence (or a close variant) causes the complex to commit to full Шаблон:Gli assembly and the start of translation. The Kozak sequence is distinct from other recognition sequences relevant to translation such as Шаблон:Gli and Шаблон:Gli.[34]
The chemical attachment of a highly selective substance, known as a label, tag, or Шаблон:Gli, to a particular cell, protein, amino acid, or other molecule of interest, either naturally or artificially, Шаблон:Gli or Шаблон:Gli. Natural labelling is a primary mechanism by which biomolecules specifically identify and interact with other biomolecules; important examples include Шаблон:Gli, Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli. Labelling is also a common laboratory technique, where the label is typically a reactive derivative of a naturally fluorescent compound (e.g. green fluorescent protein), dye, enzyme, Шаблон:Gli, radioactive molecule, or any other substance that makes its target distinguishable in some way. The labelled targets are thereby rendered distinct from their unlabelled surroundings, allowing them to be detected, identified, quantified, or isolated for further study.
In Шаблон:Gli, the nascent Шаблон:Gli for which Шаблон:Gli's direction of synthesis is away from the Шаблон:Gli, which necessitates a complex and discontinuous process in contrast to the streamlined, continuous synthesis of the other nascent strand, known as the Шаблон:Gli, which occurs simultaneously. Because DNA polymerase works only in the Шаблон:Gli to Шаблон:Gli direction, but the lagging strand's overall direction of chain elongation must ultimately be the opposite (i.e. 3' to 5', toward the replication fork), elongation must occur by an indirect mechanism in which a Шаблон:Gli enzyme synthesizes short Шаблон:GliШаблон:Gli complementary to the template DNA, and DNA polymerase then extends the primed segments into short chains of nucleotides known as Шаблон:Gli. The RNA primers are then removed and replaced with DNA, and the Okazaki fragments are joined by Шаблон:Gli.
1. Any thin layer, membrane, or plate of tissue, occurring in a wide variety of structures of various scales and with various functions; e.g. a lamella made of a sheet of lipids forms a component of the Шаблон:Gli between the cells of some tissues.
2. The leading edge of a motile cell, of which the lamellipodia is the most forward portion.
A transcriptionally active, highly de-condensed morphology assumed by certain Шаблон:Gli during the Шаблон:Gli of Шаблон:GliШаблон:Gli in the Шаблон:Gli of Шаблон:Gli in female insects, amphibians, birds, and some other animals. Lampbrush chromosomes are conspicuous under the microscope because the Шаблон:GliШаблон:Gli, still attached at Шаблон:Gli, are gigantically elongated into large loops of unpackaged Шаблон:Gli extending laterally from a series of Шаблон:Gli. Large numbers of Шаблон:Gli and Шаблон:Gli are transcribed from the lateral loops, generating a rich pool of Шаблон:Gli to be used in the immature oocyte and after fertilization, with functions in both Шаблон:Gli and Шаблон:Gli. Because they allow individual Шаблон:Gli to be directly visualized, lampbrush chromosomes are useful models for studying chromosome organization and genome structure and for constructing high-resolution chromosome maps.[35]
A Шаблон:Gli magnified 11,000 times with an electron microscope, showing the characteristic lateral loops containing transcriptionally active segments of DNA
In Шаблон:Gli, the nascent Шаблон:Gli for which both the direction of synthesis by Шаблон:Gli and the direction of overall chain elongation are toward the Шаблон:Gli; i.e. both occur in the Шаблон:Gli to Шаблон:Gli direction, resulting in a single, continuous elongation process with few or no interruptions. By contrast, the other nascent strand, known as the Шаблон:Gli, is assembled in a discontinuous process involving the ligation of short Шаблон:Gli synthesized in the opposite direction, away from the replication fork.[6]
In Шаблон:Gli, the first of five substages of Шаблон:Gli, following Шаблон:Gli and preceding Шаблон:Gli. During leptonema, the replicated chromosomes condense from diffuse Шаблон:Gli into long, thin strands that are much more visible within the Шаблон:Gli.
A common structural Шаблон:Gli in Шаблон:GliШаблон:Gli and some other types of proteins, approximately 35 amino acids in length, characterized chiefly by the recurrence of the amino acid leucine every seven residues. When modeled in an idealized Шаблон:Gli conformation, the leucine residues are positioned in such a way that they can interdigitate with the same or similar motifs in an alpha helix belonging to another similar polypeptide, facilitating Шаблон:Gli and the formation of a complex resembling a zipper.[4]
In biochemistry, any molecule that binds to or interacts with a Шаблон:Gli on a Шаблон:Gli or other Шаблон:Gli, usually reversibly via intermolecular forces;[8] or any substance that forms a complex with a biomolecule as part of a biological process. The binding of specific ligands to DNA or proteins is important in many Шаблон:Gli; for example, protein–ligand binding may result in the protein undergoing a Шаблон:Gli which alters its function or affinity for other molecules.
The joining of consecutive Шаблон:Gli in the same Шаблон:Gli of a Шаблон:Gli molecule via the formation of a Шаблон:Gli between the Шаблон:Gli of one nucleotide and the Шаблон:Gli of an adjacent nucleotide, a condensation reaction catalyzed by enzymes known as Шаблон:Gli.[10] This reaction occurs in fundamentally the same way in all varieties of Шаблон:Gli and Шаблон:Gli anabolism, natural or artificial, whether the addition of individual nucleotides to a growing strand (as in Шаблон:Gli and Шаблон:Gli), or the Шаблон:Gli of Шаблон:Gli and Шаблон:Gli in previously intact molecules, or the joining of separate nucleic acid fragments into a single molecule (as in Шаблон:Gli, Шаблон:Gli, retroviral Шаблон:Gli, and all other forms of Шаблон:Gli, as well as artificial Шаблон:Gli techniques). Ligation is the opposite of the catabolic reaction wherein phosphodiester bonds are cleaved by Шаблон:Gli. It also should not be confused with the non-covalent Шаблон:Gli that can occur between complementary strands; ligation refers specifically to the synthesis of the Шаблон:Gli of a single strand.
The tendency of DNA sequences which are physically near to each other on the same chromosome to be Шаблон:Gli together during Шаблон:Gli. Because the physical distance between them is relatively small, the chance that any two nearby parts of a DNA sequence (often Шаблон:Gli or Шаблон:Gli) will be separated on to different Шаблон:Gli during Шаблон:Gli is statistically very low; such loci are then said to be more linked than loci that are farther apart. Loci that exist on entirely different chromosomes are said to be perfectly unlinked. The standard unit for measuring genetic linkage is the Шаблон:Gli (cM).
1. A short, synthetic DNA duplex containing the Шаблон:Gli for a particular Шаблон:Gli.[6] In Шаблон:Gli, linkers are often deliberately included in Шаблон:Gli molecules in order to make them easily modifiable by permitting cleavage and Шаблон:Gli of foreign sequences at precise locations. A segment of an engineered Шаблон:Gli containing many such restriction sites is sometimes called a Шаблон:Gli.
The number of times that the two strands of a circular Шаблон:GliШаблон:Gli molecule cross each other, equivalent to the Шаблон:Gli (which measures the torsion of the double helix) plus the Шаблон:Gli (which measures the degree of supercoiling). The linking number of a closed molecule cannot be changed without breaking and rejoining the strands. DNA molecules which are identical except for their linking numbers are known as topological isomers.[6]
Any of a heterogeneous class of organic compounds, including Шаблон:Gli (fats), waxes, sterols, and some vitamins, united only by their amphipathic or Шаблон:Gli nature and consequently their very low solubility in water.[4] Some lipids such as Шаблон:Gli tend to form lamellar structures or micelles in aqueous environments, where they serve as the primary constituents of biological Шаблон:Gli. Others such as Шаблон:Gli can be Шаблон:Gli for energy, have important functions in energy storage, or serve as Шаблон:Gli molecules. Colloquially, the term "lipids" is sometimes used as a synonym for fats, though fats are more correctly considered a subclass of lipids.
A lamellar structure composed of numerous amphipathic Шаблон:Gli molecules packed together in two back-to-back sheets or layers, with their Шаблон:GliШаблон:Gli "tails" directed inward and their Шаблон:Gli "heads" exposed on the outer surface. This is the basic structural motif for all biological Шаблон:Gli, including the Шаблон:Gli surrounding all cells as well as the membranes surrounding Шаблон:Gli and Шаблон:Gli. Though bilayers are sometimes colloquially described as phospholipid bilayers, Шаблон:Gli are just one of several classes of Шаблон:Gli which form bilayers; most membranes are actually a Шаблон:Gli of phospholipids, Шаблон:Gli, and Шаблон:Gli, interspersed and studded with various other molecules such as Шаблон:Gli.[4]
Any water-soluble Шаблон:Gli to which one or more lipid molecules are attached by covalent bonding to amino acid residues. Many classes of lipids can be conjugated to proteins, including Шаблон:Gli, Шаблон:Gli, and Шаблон:Gli.[3] Compare Шаблон:Gli.
1. Any small, natural Шаблон:Gli globule, such as a micelle, occurring naturally in the cytoplasm;[3] they are commonly formed by budding off from larger membrane-bound vesicles.
2. A small, spherical, artificial Шаблон:Gli having at least one continuous Шаблон:Gli of lipid molecules enclosing some of the medium in which it is suspended.[36] Liposomes can be created in the laboratory by disrupting existing biological membranes and allowing complex lipids to form bilayer-bound vesicles in aqueous solution, usually with the aid of Шаблон:Gli. They are used experimentally as models of natural membranes and also therapeutically for the encapsulation and delivery of pharmaceutical compounds, enzymes, nutrients, nucleic acids, lipid-based nanoparticles (as in some vaccines), and many other agents between or inside of cells.[3]
In condensed Шаблон:Gli where the positioning of the Шаблон:Gli creates two segments or "arms" of unequal length, the longer of the two arms of a Шаблон:Gli. Contrast Шаблон:Gli.
Any of a large family of non-Шаблон:GliШаблон:Gli which together comprises one of the most widespread Шаблон:Gli in eukaryotic genomes. Each LINE Шаблон:Gli is on average about 7,000 base pairs in length.
The disruption and decomposition of the Шаблон:Gli surrounding a cell, or more generally of any membrane-bound Шаблон:Gli or Шаблон:Gli, especially by Шаблон:Gli, Шаблон:Gli, or other chemical or mechanical processes which compromise the membrane's integrity and thereby cause the unobstructed interchange of the contents of Шаблон:Gli and Шаблон:Gli spaces. Lysis generally implies the complete and irreversible loss of intracellular organization as a result of the release of the cell's internal components and the dilution of the Шаблон:Gli, and therefore the death of the cell. Such a cell is said to be lysed, and a fluid containing the contents of lysed cells (usually including Шаблон:Gli, Шаблон:Gli, and many other organic molecules) is called a lysate. Lysis may occur both naturally and artificially, and is a normal part of the cellular life cycle.
↑Morgan, G.T. (2002) "Lampbrush chromosomes and associated bodies: new insights into principles of nuclear structure and function." Chromosome Research. 10: 177–200.
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