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The '''history of genetics''' dates from the [[classical era]] with contributions by [[Pythagoras]], [[Hippocrates]], [[Aristotle]], [[Epicurus]], and others. Modern genetics began with the work of the [[Augustinian friar]] [[Gregor Johann Mendel]]. [[Experiments on Plant Hybridisation|His works]] on pea plants, published in 1866, provided the initial evidence that, on its rediscovery in the 1900s, helped to establish the theory of [[Mendelian inheritance]].

In [[ancient Greece]], Hippocrates suggested that all organs of the body of a parent gave off invisible "seeds", miniaturised components that were transmitted during sexual intercourse and combined in the mother's womb to form a baby. In the [[early modern period]], [[William Harvey]]'s
book ''On Animal Generation'' contradicted [[Aristotle's biology|Aristotle's theories of genetics and embryology]].

The 1900 rediscovery of Mendel's work by [[Hugo de Vries]], [[Carl Correns]] and [[Erich von Tschermak]] led to rapid advances in genetics. By 1915 the basic principles of Mendelian genetics had been studied in a wide variety of organisms – most notably the fruit fly ''[[Drosophila melanogaster]]''. Led by [[Thomas Hunt Morgan]] and his fellow "drosophilists", geneticists developed the [[Mendelian]] model, which was widely accepted by 1925. Alongside experimental work, mathematicians developed the statistical framework of [[population genetics]], bringing genetic explanations into the study of [[evolution]].

With the basic patterns of genetic inheritance established, many biologists turned to investigations of the physical nature of the [[gene]]. In the 1940s and early 1950s, experiments pointed to [[DNA]] as the portion of chromosomes (and perhaps other nucleoproteins) that held genes. A focus on new model organisms such as viruses and bacteria, along with the [[History of molecular biology#Discovery of the structure of DNA|discovery of the double helical structure of DNA]] in 1953, marked the transition to the era of [[molecular genetics]].

In the following years, chemists developed techniques for sequencing both nucleic acids and proteins, while many others worked out the relationship between these two forms of biological molecules and discovered the [[genetic code]]. The regulation of [[gene expression]] became a central issue in the 1960s; by the 1970s gene expression could be controlled and manipulated through [[genetic engineering]]. In the last decades of the 20th century, many biologists focused on large-scale genetics projects, such as sequencing entire genomes.

==Pre-Mendel ideas on heredity==
{{See also|Heredity|Timeline of the history of genetics}}

===Ancient theories===
[[File:Aristotle's model of Inheritance.png|thumb|left|300px|[[Aristotle's biology|Aristotle's model]] of transmission of movements from parents to child, and of [[Hylomorphism|form]] from the father. The model is not fully symmetric.<ref name=LeroiAristotle>{{cite conference |last=Leroi |first=Armand Marie |editor=Föllinger, S. |author-link=Armand Marie Leroi |title=Function and Constraint in Aristotle and Evolutionary Theory |book-title=Was ist 'Leben'? Aristoteles' Anschauungen zur Entstehung und Funktionsweise von Leben |date=2010 |publisher=Franz Steiner Verlag |pages=261–284 |isbn=978-3-515-09244-9 |oclc=276334688 |url=https://d-nb.info/998697990/04}}</ref>]]

The most influential early theories of heredity were that of [[Hippocrates]] and [[Aristotle]]. Hippocrates' theory (possibly based on the teachings of [[Anaxagoras]]) was similar to Darwin's later ideas on [[pangenesis]], involving heredity material that collects from throughout the body. [[Aristotle's biology|Aristotle suggested]] instead that the (nonphysical) [[Theory of forms|form-giving principle]] of an organism was transmitted through semen (which he considered to be a purified form of blood) and the mother's menstrual blood, which interacted in the womb to direct an organism's early development.<ref name=LeroiAristotle/> For both Hippocrates and Aristotle—and nearly all Western scholars through to the late 19th century—the [[inheritance of acquired characters]] was a supposedly well-established fact that any adequate theory of heredity had to explain. At the same time, individual species were taken to have a [[essentialism|fixed essence]]; such inherited changes were merely superficial.<ref>{{cite book |author-link=Ernst Mayr |first=Ernst |last=Mayr |title=The growth of biological thought : diversity, evolution, and inheritance |publisher=Belknap Press |date=1982 |isbn=0674364457 |oclc=7875904 |pages=635–640 |url=http://www.archive.org/details/growthofbiologic00mayr}}</ref> The Athenian philosopher [[Epicurus]] observed families and proposed the contribution of both males and females of hereditary characters ("sperm atoms"), noticed dominant and recessive types of inheritance and described segregation and independent assortment of "sperm atoms".<ref>{{cite book |first=C. |last=Yapijakis |chapter=Ancestral Concepts of Human Genetics and Molecular Medicine in Epicurean Philosophy |chapter-url=https://link.springer.com/chapter/10.1007/978-3-319-51783-4_3 |editor-last=Petermann |editor-first=H. |editor2-last=Harper |editor2-first=P. |editor3-last=Doetz |editor3-first=S. |title=History of Human Genetics |publisher=Springer |date=2017 |isbn=978-3-319-51783-4 |pages=41–57 |doi=10.1007/978-3-319-51783-4_3 |url=}}</ref>

The Roman poet and philosopher [[Lucretius]] describes heredity in his work "De rerum natura".<ref name=":0">{{Cite journal |last=Stubbe |first=Hans |date=1972 |title=History of Genetics, from Prehistory to the Rediscovery of Mendel's Laws |url=https://archive.org/details/historyofgenetic0000stub/page/51/mode/1up |journal=Cambridge: MIT Press |volume=1 |issue=50 | pages=359 |via=Internet Archive}}</ref>

<blockquote> From this semen, Venus produces a varied variety of characteristics and reproduces ancestral traits of expression, voice or hair; These features, as well as our faces, bodies, and limbs, are also determined by the specific semen of our relatives.<ref>{{Cite journal |last=Stubbe |first=Hans |date=1972 |title=History of Genetics, from prehistory to the rediscovery of Mendel's laws |url=https://archive.org/details/historyofgenetic0000stub/page/51/mode/1up |journal=Cambridge: MIT Press |volume=1 |issue=51 |pages=359 |via=Internet Archive}}</ref></blockquote>

Similarly, [[Marcus Terentius Varro]] in "Rerum rusticarum libri tres" and Publius Vergilius Maro propose that wasps and bees originate from animals like horses, calves, and donkeys, with wasps coming from horses and bees from calves or donkeys.<ref>{{Cite journal |last=Stubbe |first=Hans |date=1972 |title =History of Genetics, from Prehistory to the Rediscovery of Mendel's Laws |url=https://archive.org/details/historyofgenetic0000stub/page/51/mode/1up |journal=Cambridge: MIT Press |volume=1 |issue=53 |pages=359 |via=Internet Archive}}</ref>

In 1000 CE, the [[Medicine in medieval Islam|Arab physician]], [[Abu al-Qasim al-Zahrawi]] (known as Albucasis in the West) was the first physician to describe clearly the hereditary nature of [[haemophilia]] in his ''[[Al-Tasrif]]''.<ref name="MedievalLife">{{cite book | title=Handbook to life in the medieval world | first1=Madeleine Pelner | last1=Cosman | first2=Linda Gale | last2=Jones | publisher=Infobase Publishing | isbn=978-0-8160-4887-8 | pages=528–529| year=2008 }}</ref> In 1140 CE, [[Judah Halevi|Judah HaLevi]] described dominant and recessive genetic traits in [[The Kuzari]].<ref>HaLevi, Judah, translated and annotated by N. Daniel Korobkin. ''The Kuzari: In Defense of the Despised Faith, ''p. 38, I:95: "This phenomenon is common in genetics as well—often we find a son who does not resemble his father at all, but closely resembles his grandfather. Undoubtedly, the genetics and resemblance were dormant within the father even though they were not outwardly apparent. Hebrew by [[Judah ibn Tibbon|Ibn Tibon]], p.375: ונראה כזה בענין הטבעי, כי כמה יש מבני האדם שאינו דומה לאב כלל אך הוא דומה לאבי אביו ואין ספק כי הטבע ההוא והדמיון ההוא היה צפון באב ואף על פי שלא נראה להרגשה</ref>

===Preformation theory===
[[File:Preformation.GIF|thumb|[[Sperm]]s as preformed humans. Painting of [[Nicolaas Hartsoeker]] 1695]]
{{main|Preformationism}}
The preformation theory is a developmental biological theory, which was represented in antiquity by the Greek philosopher [[Anaxagoras]]. It reappeared in modern times in the 17th century and then prevailed until the 19th century. Another common term at that time was the theory of evolution, although "evolution" (in the sense of development as a pure growth process) had a completely different meaning than today. The preformists assumed that the entire organism was preformed in the [[sperm]] (animalkulism) or in the [[Egg cell|egg]] (ovism or ovulism) and only had to unfold and grow. This was contrasted by the theory of [[Epigenesis (biology)|epigenesis]], according to which the structures and organs of an organism only develop in the course of individual development ([[Ontogeny]]). Epigenesis had been the dominant opinion since antiquity and into the 17th century, but was then replaced by preformist ideas. Since the 19th century epigenesis was again able to establish itself as a view valid to this day.<ref>{{cite book |first=François |last=Jacob |title=Die Logik des Lebenden. Von der Urzeugung zum genetischen Code |publisher=Fischer |location=Frankfurt am Main |date=1972 |isbn=3-10-035601-2 |oclc=1200295370}}</ref><ref>{{cite book |author-link=Ilse Jahn |first1=Ilse |last1=Jahn |first2=Rolf |last2=Löther |first3=Konrad |last3=Senglaub  |title=Geschichte der Biologie: Theorien, Methoden, Institutionen, Kurzbiographien |publisher=VEB Fischer |location=Jena |edition=2nd |date=1985 |isbn=3437203290 |pages= |oclc=19780133}}</ref>

===Plant systematics and hybridisation===
{{See also|History of plant systematics}}
In the 18th century, with increased knowledge of plant and animal diversity and the accompanying increased focus on [[Taxonomy (biology)|taxonomy]], new ideas about heredity began to appear. [[Carl Linnaeus|Linnaeus]] and others (among them [[Joseph Gottlieb Kölreuter]], [[Carl Friedrich von Gärtner]], and [[Charles Naudin]]) conducted extensive experiments with hybridisation, especially [[Hybrid (biology)|hybrids]] between species. Species hybridisers described a wide variety of inheritance phenomena, include hybrid sterility and the high variability of [[back-crossing|back-crosses]].<ref>{{harvnb|Mayr|1982|pp=640–9}}</ref>

Plant breeders were also developing an array of stable [[Variety (botany)|varieties]] in many important plant species. In the early 19th century, [[Augustin Sageret]] established the concept of [[Dominance relationship|dominance]], recognising that when some plant varieties are crossed, certain characteristics (present in one parent) usually appear in the offspring; he also found that some ancestral characteristics found in neither parent may appear in offspring. However, plant breeders made little attempt to establish a theoretical foundation for their work or to share their knowledge with current work of physiology,<ref>{{harvnb|Mayr|1982|pp=649–651}}</ref> although [[Gartons Agricultural Plant Breeders]] in England explained their system.<ref>For example, Explanatory Notes, Gartons Seed Catalogue for Spring 1901</ref>

==Mendel==
[[File:Blending Inheritance.svg|thumb|Blending Inheritance]] Between 1856 and 1865, [[Gregor Mendel]] conducted breeding experiments using the pea plant ''Pisum sativum'' and traced the inheritance patterns of certain traits. Through these experiments, Mendel saw that the genotypes and phenotypes of the progeny were predictable and that some traits were dominant over others.<ref>{{Cite book|last=Pierce|first=Benjamin A.|title=Genetics A Conceptual Approach (7th ed.)|publisher=W.H. Freeman|year=2020|isbn=978-1-319-29714-5|pages=49–56}}</ref> These patterns of [[Mendelian inheritance]] demonstrated the usefulness of applying statistics to inheritance. They also contradicted 19th-century theories of [[blending inheritance]], showing, rather, that genes remain discrete through multiple generations of hybridisation.<ref>{{cite book |author-link=Siddhartha Mukherjee |first=Siddartha |last=Mukherjee |chapter=Chapter 4 |chapter-url= |editor= |title=The Gene: An intimate history |publisher=Scribner |date=2016 |isbn=978-1-4767-3353-1 |pages= |oclc=949803912}}</ref>

From his statistical analysis, Mendel defined a concept that he described as a character (which in his mind holds also for "determinant of that character"). In only one sentence of his historical paper, he used the term "factors" to designate the "material creating" the character: " So far as experience goes, we find it in every case confirmed that constant progeny can only be formed when the egg cells and the fertilising pollen are off like the character so that both are provided with the material for creating quite similar individuals, as is the case with the normal fertilisation of pure species. We must, therefore, regard it as certain that exactly similar factors must be at work also in the production of the constant forms in the hybrid plants."(Mendel, 1866).
[[File:Mendelian inheritance.svg|thumb|[[Mendelian inheritance]] states characteristics are discrete and are inherited by the parents. This image depicts a [[monohybrid cross]] and shows 3 generations: P1 generation (1), F1 generation (2), and F2 generation (3). Each organism inherits two alleles, one from each parent, that make up the genotype. The observed characteristic, the phenotype, is determined by the dominant allele in the genotype. In this monohybrid cross the dominant allele encodes for the colour red and the recessive allele encodes for the colour white.]]
Mendel's work was published in 1866 as ''"Versuche über Pflanzen-Hybriden" ([[Experiments on Plant Hybridisation]])'' in the ''Verhandlungen des Naturforschenden Vereins zu Brünn (Proceedings of the Natural History Society of Brünn)'', following two lectures he gave on the work in early 1865.<ref>{{Cite magazine|url=https://www.wired.com/2010/02/0208gregor-mendel-reads-paper/|title=Feb. 8, 1865: Mendel Reads Paper Founding Genetics|last=Alfred|first=Randy|date=2010-02-08|magazine=Wired|access-date=2019-11-11|issn=1059-1028}}</ref>

==Post-Mendel, pre-rediscovery==
===Pangenesis===
[[File:Darwin's Pangenesis.svg|thumb|upright=1.5|Diagram of [[Charles Darwin]]'s pangenesis theory. Every part of the body emits tiny particles, [[Gemmule (pangenesis)|gemmules]], which migrate to the [[gonad]]s and contribute to the fertilised egg and so to the next generation. The theory implied that changes to the body during an organism's life would be inherited, as proposed in [[Lamarckism]].]]

Mendel's work was published in a relatively obscure [[scientific journal]], and it was not given any attention in the scientific community. Instead, discussions about modes of heredity were galvanised by [[Charles Darwin|Darwin]]'s theory of [[evolution]] by natural selection, in which mechanisms of non-[[Lamarckian]] heredity seemed to be required. Darwin's own theory of heredity, [[pangenesis]], did not meet with any large degree of acceptance.<ref>{{cite journal |author-link=Charles Darwin |first=C.R. |last=Darwin |title=Pangenesis |journal=Nature |volume=3  |issue=78 |pages=502–3 |date=27 April 1871 |doi=10.1038/003502a0 |bibcode=1871Natur...3..502D |url=http://darwin-online.org.uk/content/frameset?itemID=F1751&viewtype=side&pageseq=1}}</ref><ref name="Geison69">{{cite journal | last1=Geison | first1=G. L. | year=1969 | title=Darwin and heredity: The evolution of his hypothesis of pangenesis | journal=J Hist Med Allied Sci | volume=XXIV | issue=4 | pages=375–411 | doi=10.1093/jhmas/XXIV.4.375| pmid=4908353 }}</ref> A more mathematical version of pangenesis, one which dropped much of Darwin's Lamarckian holdovers, was developed as the "biometrical" school of heredity by Darwin's cousin, [[Francis Galton]].<ref>{{cite book |last=Bulmer |first=M. G. |year=2003 |title=Francis Galton: Pioneer of Heredity and Biometry |publisher=Johns Hopkins University Press |url=https://books.google.com/books?id=rjnQ_YmtdcEC |isbn=978-0-801-88140-4 |pages=116–8}}</ref>

===Germ plasm===
[[File:Weismann's Germ Plasm.svg|thumb|upright=1.5|[[August Weismann]]'s germ plasm theory. The hereditary material, the germ plasm, is confined to the [[gonad]]s. Somatic cells (of the body) [[embryology|develop afresh]] in each generation from the germ plasm.]]

In 1883 [[August Weismann]] conducted experiments involving breeding mice whose tails had been surgically removed. His results — that surgically removing a mouse's tail had no effect on the tail of its offspring — challenged the theories of pangenesis and [[Lamarckism]], which held that changes to an organism during its lifetime could be inherited by its descendants. Weismann proposed the [[germ plasm]] theory of inheritance, which held that hereditary information was carried only in sperm and egg cells.<ref name="Mukherjee_ch5">{{harvnb|Mukherjee|2016|loc=Chapter 5}}</ref>

==Rediscovery of Mendel==
[[Hugo de Vries]] wondered what the nature of germ plasm might be, and in particular he wondered whether or not germ plasm was mixed like paint or whether the information was carried in discrete packets that remained unbroken. In the 1890s he was conducting breeding experiments with a variety of plant species and in 1897 he published a paper on his results that stated that each inherited trait was governed by two discrete particles of information, one from each parent, and that these particles were passed along intact to the next generation. In 1900 he was preparing another paper on his further results when he was shown a copy of Mendel's 1866 paper by a friend who thought it might be relevant to de Vries's work. He went ahead and published his 1900 paper without mentioning Mendel's priority. Later that same year another botanist, [[Carl Correns]], who had been conducting hybridisation experiments with maize and peas, was searching the literature for related experiments prior to publishing his own results when he came across Mendel's paper, which had results similar to his own. Correns accused de Vries of appropriating terminology from Mendel's paper without crediting him or recognising his priority. At the same time another botanist, [[Erich von Tschermak]] was experimenting with pea breeding and producing results like Mendel's. He too discovered Mendel's paper while searching the literature for relevant work. In a subsequent paper de Vries praised Mendel and acknowledged that he had only extended his earlier work.<ref name="Mukherjee_ch5"/>

==Emergence of molecular genetics==
After the rediscovery of Mendel's work there was a feud between [[William Bateson]] and [[Karl Pearson|Pearson]] over the hereditary mechanism, solved by [[Ronald Fisher]] in his work "[[The Correlation Between Relatives on the Supposition of Mendelian Inheritance]]".

[[File:Sexlinked inheritance white.jpg|left|thumb|upright=1.3|[[Thomas Hunt Morgan]] discovered [[sex linked]] inheritance of the white eyed mutation in the fruit fly ''[[Drosophila melanogaster|Drosophila]]'' in 1910, implying the [[gene]] was on the [[sex chromosome]].]]

In 1910, [[Thomas Hunt Morgan]] showed that genes reside on specific [[chromosome]]s. He later showed that genes occupy specific locations on the chromosome. With this knowledge, [[Alfred Sturtevant]], a member of Morgan's famous [[fly room]], using ''[[Drosophila melanogaster]],'' provided the first chromosomal map of any biological organism. In 1928, [[Frederick Griffith]] showed that genes could be transferred. In what is now known as [[Griffith's experiment]], injections into a mouse of a deadly strain of [[bacteria]] that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse.

A series of subsequent discoveries (e.g.<ref>{{cite journal |vauthors=Hershey AD, Chase M |title=Independent functions of viral protein and nucleic acid in growth of bacteriophage |journal=J Gen Physiol |volume=36 |issue=1 |pages=39–56 |date=May 1952 |doi=10.1085/jgp.36.1.39 |pmid=12981234 |pmc=2147348}}</ref>) led to the realization decades later that the genetic material is made of [[DNA]] (deoxyribonucleic acid) and not, as was widely believed until then, of proteins. In 1941, [[George Wells Beadle]] and [[Edward Lawrie Tatum]] showed that mutations in genes caused errors in specific steps of [[metabolic pathway]]s.<ref>{{cite journal |vauthors=Beadle GW, Tatum EL |title=Genetic Control of Biochemical Reactions in Neurospora |journal=Proc Natl Acad Sci U S A |volume=27 |issue=11 |pages=499–506 |date=November 1941 |doi=10.1073/pnas.27.11.499 |doi-access=free |pmid=16588492 |pmc=1078370|bibcode=1941PNAS...27..499B }}</ref> This showed that specific genes code for specific proteins, leading to the "[[one gene, one enzyme]]" hypothesis.<ref name="Gerstein">{{cite journal | vauthors=Gerstein MB, Bruce C, Rozowsky JS, Zheng D, Du J, Korbel JO, Emanuelsson O, Zhang ZD, Weissman S, Snyder M | title=What is a gene, post-ENCODE? History and updated definition | journal=Genome Research | volume=17 | issue=6 | pages=669–681 | date=June 2007 | pmid=17567988 | doi=10.1101/gr.6339607 | doi-access=free }}</ref> [[Oswald Avery]], [[Colin Munro MacLeod]], and [[Maclyn McCarty]] [[Avery-MacLeod-McCarty experiment|showed in 1944]] that DNA holds the gene's information.<ref>{{cite journal | vauthors=Steinman RM, Moberg CL | title=A triple tribute to the experiment that transformed biology | journal=The Journal of Experimental Medicine | volume=179 | issue=2 | pages=379–84 | date=February 1994 | pmid=8294854 | pmc=2191359 | doi=10.1084/jem.179.2.379 }}</ref> In 1952, [[Rosalind Franklin]] and [[Raymond Gosling]] produced a strikingly clear x-ray diffraction pattern indicating a helical form. Using these x-rays and information already known about the chemistry of DNA, [[James D. Watson]] and [[Francis Crick]] demonstrated the molecular structure of [[DNA]] in 1953.<ref>{{Cite book|last=Pierce|first=Benjamin A.|title=Genetics A Conceptual Approach (7th ed.)|publisher=W.H. Freeman|year=2020|isbn=978-1-319-29714-5|location=New York|pages=299–300}}</ref><ref>{{cite journal |vauthors=Watson JD, Crick FH |title=Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid |journal=Nature |volume=171 |issue=4356 |pages=737–8 |date=25 April 1953 |doi=10.1038/171737a0 |pmid=13054692|bibcode=1953Natur.171..737W }}</ref> Together, these discoveries established the [[central dogma of molecular biology]], which states that proteins are translated from [[RNA]] which is transcribed by DNA. This dogma has since been shown to have exceptions, such as [[reverse transcription]] in [[retrovirus]]es.

In 1947, Salvador Luria discovered the reactivation of irradiated phage<ref>{{cite journal |vauthors=Luria SE |title=Reactivation of Irradiated Bacteriophage by Transfer of Self-Reproducing Units |journal=Proc Natl Acad Sci U S A |volume=33 |issue=9 |pages=253–264 |date=September 1947 |doi=10.1073/pnas.33.9.253 |doi-access=free |pmid=16588748 |pmc=1079044|bibcode=1947PNAS...33..253L }}</ref> leading to many further studies on the fundamental processes of repair of DNA damage (for review of early studies, see <ref>{{cite journal |vauthors=Bernstein C |title=Deoxyribonucleic acid repair in bacteriophage |journal=Microbiol Rev |volume=45 |issue=1 |pages=72–98 |date=March 1981 |doi=10.1128/mr.45.1.72-98.1981 |pmid=6261109 |pmc=281499}}</ref>). In 1958, Meselson and Stahl demonstrated that DNA replicates semiconservatively, leading to the understanding that each of the individual strands in double-stranded DNA serves as a template for new strand synthesis.<ref>{{cite journal |vauthors=Meselson M, Stahl FW |title=The replication of DNA in ''Escherichia Coli'' |journal=Proc Natl Acad Sci U S A |volume=44 |issue=7 |pages=671–682 |date=July 1958 |doi=10.1073/pnas.44.7.671 |doi-access=free |pmid=16590258 |pmc=528642|bibcode=1958PNAS...44..671M }}</ref> In 1960, Jacob and collaborators discovered the [[operon]] which consists of a sequence of genes whose expression is coordinated by operator DNA.<ref>{{cite journal |vauthors=Jacob F, Perrin D, Sánchez C, Monod J, Edelstein S |title=The operon: a group of genes with expression coordinated by an operator |journal=C R Biol |volume=328 |issue=6 |pages=514–520 |date=2005 |orig-date=1960 |doi=10.1016/j.crvi.2005.04.005 |pmid=15999435|url=https://comptes-rendus.academie-sciences.fr/biologies/articles/10.1016/j.crvi.2005.04.005/ |url-access=subscription }}</ref>  In the period 1961 – 1967, through work in several different labs, the nature of the genetic code was determined (e.g.<ref>{{cite journal |vauthors=Crick FH, Barnett L, Brenner S, Watts-Tobin RJ |title=General nature of the genetic code for proteins |journal=Nature |volume=192 |issue= 4809|pages=1227–32 |date=December 1961 |doi=10.1038/1921227a0 |pmid=13882203 |bibcode=1961Natur.192.1227C }}</ref>).

In 1972, [[Walter Fiers]] and his team at the [[University of Ghent]] were the first to determine the sequence of a gene: the gene for [[bacteriophage MS2]] coat protein.<ref name=Min_1972>{{cite journal | vauthors=Min Jou W, Haegeman G, Ysebaert M, Fiers W | title=Nucleotide sequence of the gene coding for the bacteriophage MS2 coat protein | journal=Nature | volume=237 | issue=5350 | pages=82–8 | date=May 1972 | pmid=4555447 | doi=10.1038/237082a0 | bibcode=1972Natur.237...82J | s2cid=4153893 }}</ref> [[Richard J. Roberts]] and [[Phillip Sharp]] discovered in 1977 that genes can be split into segments. This led to the idea that one gene can make several proteins. The successful sequencing of many organisms' [[genome]]s has complicated the molecular definition of the gene. In particular, genes do not always sit side by side on [[DNA]] like discrete beads. Instead, [[region]]s of the DNA producing distinct proteins may overlap, so that the idea emerges that "genes are one long [[Continuum (theory)|continuum]]".<ref name=Pearson_2006>{{cite journal | author=Pearson, H. | title=Genetics: what is a gene? | journal=Nature | volume=441 | issue=7092 | pages=398–401 | date=May 2006 | pmid=16724031 | doi=10.1038/441398a | bibcode=2006Natur.441..398P | s2cid=4420674 | doi-access=free }}</ref><ref name="Rethink">{{cite journal | vauthors=Pennisi E | author-link=Elizabeth Pennisi | title=Genomics. DNA study forces rethink of what it means to be a gene | journal=Science | volume=316 | issue=5831 | pages=1556–7 | date=June 2007 | pmid=17569836 | doi=10.1126/science.316.5831.1556 | s2cid=36463252 | doi-access=free }}</ref> It was first hypothesised in 1986 by [[Walter Gilbert]] that neither DNA nor protein would be required in such a primitive system as that of a very early stage of the earth if RNA could serve both as a catalyst and as genetic information storage processor.

The modern study of [[genetics]] at the level of DNA is known as [[molecular genetics]], and the synthesis of molecular genetics with traditional [[Charles Darwin|Darwinian]] [[evolution]] is known as the [[Modern synthesis (20th century)|modern evolutionary synthesis]].

==See also==
*[[List of sequenced eukaryotic genomes]]
*[[History of molecular biology]]
*[[History of RNA biology|History of RNA Biology]]
*[[History of evolutionary thought]]
*[[One gene-one enzyme hypothesis]]
*[[Phage group]]

==References==
{{Reflist|30em}}

==Further reading==
{{See also|Bibliography of biology#Genetics|label 1=Bibliography of genetics}}
*[[Elof Axel Carlson]], ''Mendel's Legacy: The Origin of Classical Genetics'' (Cold Spring Harbor Laboratory Press, 2004.) {{ISBN|0-87969-675-3}}

==External links==
{{External links|section|date=January 2023}}
{{Commons category}}
*[http://www.mendelweb.org/MWolby.html Olby's "Mendel, Mendelism, and Genetics," at MendelWeb]
*{{cite encyclopedia |first=A. |last=Andrei  |title="Experiments in Plant Hybridization" (1866), by Johann Gregor Mendel |date=2013 |encyclopedia=Embryo Project Encyclopedia |publisher=Arizona State University |url=http://embryo.asu.edu/pages/experiments-plant-hybridization-1866-johann-gregor-mendel }}
*http://www.accessexcellence.org/AE/AEPC/WWC/1994/geneticstln.html
*http://www.sysbioeng.com/index/cta94-11s.jpg
*http://www.esp.org/books/sturt/history/
*http://cogweb.ucla.edu/ep/DNA_history.html
*{{cite news |title=The history of genetics |newspaper=BBC |date=2000 |url=http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2000/human_genome/749026.stm}}
*https://web.archive.org/web/20120323085256/http://www.hchs.hunter.cuny.edu/wiki/index.php?title=Modern_Science&printable=yes
*{{cite journal |first1=Oswald T. |last1=Avery |first2=Colin M. |last2=MacLeod |first3=Maclyn |last3=McCarty |title=Studies on the chemical nature of the substance inducing transformation of Pneumococcal types: Induction of transformation by a DEsoxyribonucleic acid fraction isolated from ''Pneumococcus'' Type III .  |journal=J Exp Med |volume=79 |issue=2 |pages=137–158 |date=February 1944 |doi=10.1084/jem.79.2.137 |pmid=19871359 |url=https://rupress.org/jem/article/79/2/137/4753/STUDIES-ON-THE-CHEMICAL-NATURE-OF-THE-SUBSTANCE|pmc=2135445 }}
*http://www.nature.com/physics/looking-back/crick/Crick_Watson.pdf
*{{cite journal | pmc=534157 | pmid=16589553 | volume=40 |issue = 8| year=1954 | journal=Proc. Natl. Acad. Sci. U.S.A. | pages=748–55 | last1=Todd | first1=AR | title=Chemical Structure of the Nucleic Acids | doi=10.1073/pnas.40.8.748| bibcode=1954PNAS...40..748T | doi-access=free }}
*http://www.genomenewsnetwork.org/resources/timeline/1960_mRNA.php
*https://web.archive.org/web/20120403041525/http://www.molecularstation.com/molecular-biology-images/data/503/MRNA-structure.png
*http://www.genomenewsnetwork.org/resources/timeline/1973_Boyer.php
*{{cite journal |first=Kevin |last=Struhl |title=The ''hisB463'' Mutation and Expression of a Eukaryotic Protein in ''Escherichia coli'' |journal=Genetics |volume=180 |issue=2 |pages=709–714 |date=1 October 2008 |doi=10.1534/genetics.104.96693 |pmid=18927256 |url=http://www.genetics.org/cgi/content/full/180/2/709|pmc=2567374 }}
*{{cite journal | pmc=431765 | pmid=271968 | volume=74 |issue = 12| title=DNA sequencing with chain-terminating inhibitors | date=December 1977 | journal=Proc. Natl. Acad. Sci. U.S.A. | pages=5463–7 | last1=Sanger | first1=F |author-link1=Frederick Sanger| last2=Nicklen | first2=S | last3=Coulson | first3=AR|author-link3=Alan Coulson | doi=10.1073/pnas.74.12.5463| bibcode=1977PNAS...74.5463S | doi-access=free }}
*{{cite journal | volume=316 | issue=6023 | doi=10.1038/316076a0 | title=Individual-specific 'fingerprints' of human DNA | journal=Nature | pages=76–79 | pmid=2989708 | year=1985 | last1=Jeffreys | first1=AJ|author-link1= Alec Jeffreys| last2=Wilson | first2=V | last3=Thein | first3=SL|author-link3= Swee Lay Thein| bibcode=1985Natur.316...76J | s2cid=4229883 | doi-access=free }}
*{{cite journal | doi=10.1146/annurev.bi.55.070186.003123 | pmid=2427016 | volume=55 | title=Biological Catalysis by RNA | journal=Annual Review of Biochemistry | pages=599–629|year = 1986|last1 = Cech|first1 = T. R.| last2=Bass | first2=B. L. }}
*{{cite news |title=A sheep cloning how-to, more or less |newspaper=CNN |date=February 1997 |url=http://www.cnn.com/TECH/9702/24/cloning.explainer/index.html}}
*{{cite web |title=Human Genome Project |type=Fact Sheet |publisher=National Human Genome Research Institute |url=https://www.genome.gov/about-genomics/educational-resources/fact-sheets/human-genome-project}}

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{{DEFAULTSORT:History Of Genetics}}
[[Category:History of genetics| ]]
[[Category:Genetics|*]]
[[Category:History of biology by subdiscipline|Genetics]]
[[Category:Gregor Mendel]]
[[Category:History of science by discipline|Genetics]]