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{{short description|Distinction between germ cell lineages producing gametes and somatic cells}}
[[File:Weismann's Germ Plasm.svg|thumb|upright=1.5|Diagram of [[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. Whatever may happen to those cells does not affect the next generation.]]
The '''Weismann barrier''', proposed by [[August Weismann]], is the strict distinction between the "immortal" germ cell lineages producing gametes and "disposable" somatic cells in animals (but not plants), in contrast to [[Charles Darwin]]'s proposed [[pangenesis]] mechanism for inheritance.<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><ref>{{cite web |last1=You |first1=Yawen |title=The Germ-Plasm: a Theory of Heredity (1893), by August Weismann |url=https://embryo.asu.edu/pages/germ-plasm-theory-heredity-1893-august-weismann |website=The Embryo Project Encyclopedia (Arizona State University) |access-date=7 September 2018 |date=26 January 2015}}</ref>

In more precise terminology, hereditary information is copied only from [[germline]] cells to [[somatic cells]]. This means that new information from somatic mutation is not passed on to the germline. This ''barrier'' concept implies that somatic mutations are not inherited.<ref>{{cite journal|last=Gauthier|first=Peter|date=March–May 1990|title=Does Weismann's Experiment Constitute a Refutation of the Lamarckian Hypothesis?|journal=BIOS|volume=61|pages=6–8|jstor=4608123|number=1/2}}</ref><ref>This does not refer to the [[central dogma of molecular biology]], which states that no sequential information can travel from [[protein]] to [[DNA]] or [[RNA]], but both hypotheses relate to a gene-centric view of life. {{cite journal |last1=De Tiege|first1=Alexis|last2=Tanghe |first2=Koen |last3=Braeckman |first3=Johan|last4=Van de Peer |first4=Yves|title=From DNA- to NA-centrism and the conditions for gene-centrism revisited |journal=Biology & Philosophy|date=January 2014 |volume=29 |issue=1 |pages=55–69 |doi=10.1007/s10539-013-9393-z|s2cid=85866639 }}</ref>

Weismann set out the concept in his 1892 book ″Das Keimplasma: eine Theorie der Vererbung″ (German for ''The [[Germ plasm|Germ Plasm]]: a theory of inheritance'').<ref>{{cite book |author=Weismann, August |date=1892 |title=Das Keimplasma: eine Theorie der Vererbung |url=https://archive.org/details/bub_gb_f5U-AAAAYAAJ |publisher=Fischer |location=Jena}}</ref> The use of this theory, commonly in the context of the [[germ plasm]] theory of the late 19th century, before the development of better-based and more sophisticated concepts of genetics in the early 20th century, is sometimes referred to as '''Weismannism'''.<ref name="GJR">{{cite book |last=Romanes |first=George John |title=An examination of Weismannism |publisher=Open court |location=Chicago |year=1893 |ol=23380098M }}</ref> Some authors distinguish '''Weismannist development''' (either [[Preformationism|preformistic]] or [[Epigenesis (biology)|epigenetic]]) that in which there is a distinct germline, from [[somatic embryogenesis]].<ref>{{cite book |last=Ridley |first=Mark |author-link=Mark Ridley (zoologist) |year=2004 |title=Evolution |edition=3rd |publisher=Blackwell |pages=295–297 }}</ref> This type of development is correlated with the [[Evolution of aging|evolution of death]] of the somatic line.

The Weismann barrier was of great importance in its day and among other influences it effectively banished certain [[Lamarckism|Lamarckian]] concepts: in particular, it would make Lamarckian inheritance from changes to the body (the soma) difficult or impossible.<ref name="Romanes 1893">{{cite book |last=Romanes |first=George John |author-link=George Romanes |title=An examination of Weismannism |publisher=Open Court |year=1893 |ol=23380098M }}</ref> It remains important, but has however required qualification in the light of modern understanding of [[horizontal gene transfer]] and some other genetic and histological developments.<ref>{{cite web |last1=Lindley |first1=Robyn A. |title=How Mutational and Epigenetic Changes Enable Adaptive Evolution |url=https://www.laboratory-journal.com/science/life-sciences-biotech/how-mutational-and-epigenetic-changes-enable-adaptive-evolution |website=G. I. T. Laboratory Journal |access-date=2018-09-07 |archive-date=2011-08-29 |archive-url=https://web.archive.org/web/20110829211956/http://www.laboratory-journal.com/science/life-sciences-biotech/how-mutational-and-epigenetic-changes-enable-adaptive-evolution }}</ref>

==Immortality of the germline==
The Russian biologist and historian [[Zhores A. Medvedev]], reviewing Weismann's theory a century later, considered that the accuracy of [[genome]] replicative and other synthetic systems alone could not explain the "immortal" [[germline|germ cell lineages]] proposed by Weismann. Rather Medvedev thought that known features of the biochemistry and genetics of [[sexual reproduction]] indicated the presence of unique information maintenance and restoration processes at the different stages of [[gametogenesis]]. In particular, Medvedev considered that the most important opportunities for information maintenance of [[germ cell]]s are created by [[genetic recombination|recombination during meiosis]] and [[DNA repair]]; he saw these as processes within the germ cells that were capable of restoring the integrity of [[DNA]] and [[chromosome]]s from the types of damage that caused irreversible ageing in [[somatic cell]]s.<ref name="Medvedev1981">{{cite journal |last=Medvedev |first=Zhores A. |title=On the immortality of the germ line: Genetic and biochemical mechanisms. A review |journal=Mechanisms of Ageing and Development |volume=17 |issue=4 |year=1981 |pages=331–359 |issn=0047-6374 |doi=10.1016/0047-6374(81)90052-X|pmid=6173551 |s2cid=35719466 }}</ref>

==Basal animals==
[[Basal animals]] such as sponges ([[Porifera]]) and corals ([[Anthozoa]]) contain multipotent stem cell lineages, that give rise to both somatic and reproductive cells. The Weismann barrier appears to be of a more recent evolutionary origin among animals.<ref>{{Cite journal|last1=Radzvilavicius|first1=Arunas L.|last2=Hadjivasiliou|first2=Zena|last3=Pomiankowski|first3=Andrew|last4=Lane|first4=Nick|date=2016-12-20|title=Selection for Mitochondrial Quality Drives Evolution of the Germline |journal=PLOS Biology|volume=14|issue=12|article-number=e2000410|doi=10.1371/journal.pbio.2000410|issn=1545-7885|pmc=5172535|pmid=27997535 |doi-access=free }}</ref>

==Plants==
In plants, genetic changes in somatic lines can and do result in genetic changes in the germ lines, because the germ cells are produced by somatic cell lineages (vegetative [[meristem]]s), which may be old enough (many years) to have accumulated multiple mutations since seed germination, some of them subject to natural selection.<ref>{{cite journal | last1 = Whitham | first1 = T.G. | last2 = Slobodchikoff | first2 = C.N. | year = 1981 | title = Evolution by individuals, plant-herbivore interactions, and mosaics of genetic variability: The adaptive significance of somatic mutations in plants | journal = Oecologia | volume = 49 | issue = 3| pages = 287–292 | doi = 10.1007/BF00347587 | pmid=28309985| bibcode = 1981Oecol..49..287W | s2cid = 20411802 }}</ref> It is noteworthy in this context that, generally speaking, adult, reproducing plants tend to produce many more offspring in number than animal organisms.

== See also ==
* {{annotated link|Alternatives to evolution by natural selection}}
* {{annotated link|Baldwin effect}}
* {{annotated link|Transgenerational epigenetic inheritance}}
* {{annotated link|Lamarckism}}
* {{annotated link|Pangenesis}}

==References==
{{reflist}}

[[Category:Genetics]]
[[Category:Lamarckism]]
[[Category:1892 in science]]
[[Category:1892 in Germany]]

Weismann barrier - История изменений

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