Editing Inbreeding (section)

{{Short description|Reproduction by closely related organisms}}
{{redirect|Inbred}}
{{For|reproduction by which offspring arise from a single organism|Asexual reproduction}}
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[[File:Child_first_cousins_Homozy_BD.png|thumb|right|The passage of [[homozygous]] alleles through an inbred pedigree]]

'''Inbreeding''' is the production of [[offspring]] from the [[mating]] or breeding of individuals or [[organism]]s that are closely [[genetic distance|related genetically]].<ref>{{Britannica|284509|Inbreeding}}</ref> By analogy, the term is used in [[human reproduction]], but more commonly refers to the genetic disorders and other consequences that may arise from expression of [[wikt:deleterious|deleterious]] [[dominance (genetics)|recessive]] traits resulting from [[incest]]uous sexual relationships and [[consanguinity]]. Animals avoid inbreeding only rarely.<ref name="nature.com">{{Cite journal |last1=de Boer |first1=Raïssa A. |last2=Vega-Trejo |first2=Regina |last3=Kotrschal |first3=Alexander |last4=Fitzpatrick |first4=John L. |date=July 2021 |title=Meta-analytic evidence that animals rarely avoid inbreeding |url=https://www.nature.com/articles/s41559-021-01453-9 |journal=Nature Ecology & Evolution |language=en |volume=5 |issue=7 |pages=949–964 |doi=10.1038/s41559-021-01453-9 |pmid=33941905 |bibcode=2021NatEE...5..949D |s2cid=233718913 |issn=2397-334X|url-access=subscription }}</ref>

Inbreeding results in [[homozygous|homozygosity]] which can increase the chances of offspring being affected by recessive [[phenotypic trait|traits]].<ref>{{cite journal | vauthors = Nabulsi MM, Tamim H, Sabbagh M, Obeid MY, Yunis KA, Bitar FF | title = Parental consanguinity and congenital heart malformations in a developing country | journal = American Journal of Medical Genetics. Part A | volume = 116A | issue = 4 | pages = 342–7 | date = February 2003 | pmid = 12522788 | doi = 10.1002/ajmg.a.10020 | s2cid = 44576506 }}</ref> In extreme cases, this usually leads to at least temporarily decreased [[Fitness (biology)|biological fitness]] of a [[population]]<ref>{{cite journal|author-link2=Kimberly Hughes | vauthors = Jiménez JA, Hughes KA, Alaks G, Graham L, Lacy RC | title = An experimental study of inbreeding depression in a natural habitat | journal = Science | volume = 266 | issue = 5183 | pages = 271–3 | date = October 1994 | pmid = 7939661 | doi = 10.1126/science.7939661 | bibcode = 1994Sci...266..271J }}</ref><ref>{{cite journal| vauthors = Chen X |doi=10.1038/hdy.1993.163|title=Comparison of inbreeding and outbreeding in hermaphroditic ''Arianta arbustorum'' (L.) (land snail)|year=1993|journal=Heredity|volume=71|issue=5 |pages=456–461|doi-access=free|bibcode=1993Hered..71..456C }}</ref> (called [[inbreeding depression]]), which is its ability to survive and reproduce. An individual who inherits such deleterious traits is colloquially referred to as ''inbred''. The avoidance of expression of such deleterious recessive [[allele]]s caused by inbreeding, via [[inbreeding avoidance]] mechanisms, is the main selective reason for outcrossing.<ref name="Bernstein H 1985">{{cite journal | vauthors = Bernstein H, Byerly HC, Hopf FA, Michod RE | title = Genetic damage, mutation, and the evolution of sex | journal = Science | volume = 229 | issue = 4719 | pages = 1277–81 | date = September 1985 | pmid = 3898363 | doi = 10.1126/science.3898363 | bibcode = 1985Sci...229.1277B }}</ref><ref name="Michod RE 1994">Michod RE. Eros and Evolution: A Natural Philosophy of Sex. (1994) Perseus Books, {{ISBN|0-201-40754-X}}</ref> Crossbreeding between populations sometimes has positive effects on fitness-related traits,<ref>{{cite journal | last = Lynch | first = Michael | year =  1991 | title = The Genetic Interpretation of Inbreeding Depression and Outbreeding Depression. | journal = Evolution; International Journal of Organic Evolution | volume = 45 | issue = 3 | pages = 622–629 | location = Oregon | publisher = Society for the Study of Evolution | doi = 10.1111/j.1558-5646.1991.tb04333.x | pmid = 28568822 | s2cid = 881556 | doi-access = free }}{{page needed|date=August 2018}}</ref> but also sometimes leads to negative effects known as [[outbreeding depression]]. However, increased homozygosity increases the probability of fixing beneficial alleles and also slightly decreases the probability of fixing deleterious alleles in a population.<ref name="pmid12807795">{{cite journal |vauthors=Whitlock MC |title=Fixation probability and time in subdivided populations |journal=Genetics |volume=164 |issue=2 |pages=767–79 |date=June 2003 |doi=10.1093/genetics/164.2.767 |pmid=12807795 |pmc=1462574 }}</ref> Inbreeding can result in purging of deleterious alleles from a population through [[purifying selection]].<ref name="nih">{{cite journal | vauthors = Tien NS, Sabelis MW, Egas M | title = Inbreeding depression and purging in a haplodiploid: gender-related effects | journal = Heredity | volume = 114 | issue = 3 | pages = 327–32 | date = March 2015 | pmid = 25407077 | pmc = 4815584 | doi = 10.1038/hdy.2014.106 | bibcode = 2015Hered.114..327T }}</ref><ref>{{cite journal | vauthors = Peer K, Taborsky M | title = Outbreeding depression, but no inbreeding depression in haplodiploid Ambrosia beetles with regular sibling mating | journal = Evolution; International Journal of Organic Evolution | volume = 59 | issue = 2 | pages = 317–23 | date = February 2005 | pmid = 15807418 | doi=10.1554/04-128| s2cid = 198156378 }}</ref><ref>{{cite journal | vauthors = Gulisija D, Crow JF | title = Inferring purging from pedigree data | journal = Evolution; International Journal of Organic Evolution | volume = 61 | issue = 5 | pages = 1043–51 | date = May 2007 | pmid = 17492959 | doi = 10.1111/j.1558-5646.2007.00088.x | s2cid = 24302475 }}</ref>

Inbreeding is a technique used in [[selective breeding]]. For example, in [[livestock breeding]], breeders may use inbreeding when trying to establish a new and desirable [[Phenotypic trait|trait]] in the stock and for producing distinct families within a breed, but will need to watch for undesirable characteristics in offspring, which can then be eliminated through further selective breeding or [[culling]]. Inbreeding also helps to ascertain the type of gene action affecting a trait. Inbreeding is also used to reveal deleterious recessive alleles, which can then be eliminated through [[assortative mating|assortative breeding]] or through culling. In [[plant breeding]], [[inbred line]]s are used as stocks for the creation of [[Hybrid (biology)|hybrid]] lines to make use of the effects of [[heterosis]]. Inbreeding in plants also occurs naturally in the form of [[self-pollination]].

Inbreeding can significantly influence [[gene expression]] which can prevent inbreeding depression.<ref name="Gene-Expression Changes">{{cite journal | title = Gene-Expression Changes Caused by Inbreeding Protect Against Inbreeding Depression in Drosophila | pmc=3430533 | pmid=22714404 | doi=10.1534/genetics.112.142687 | volume=192 | issue=1 | year=2012 | journal=Genetics | pages=161–72 | vauthors=García C, Avila V, Quesada H, Caballero A}}</ref>