Genetic admixture

Genetic admixture is the presence of DNA in an individual from a distantly-related population or species, as a result of interbreeding between populations or species who have been reproductively isolated and genetically differentiated.[1][2] Admixture results in the introduction of new genetic lineages into a population. It has been known to slow local adaptation by introducing foreign, unadapted genotypes (known as genetic pollution). It also prevents speciation by homogenizing populations and increasing heterozygosity.

Examples

Climatic cycles facilitate genetic admixture in cold periods and genetic diversification in warm periods.[3] Natural flooding can cause genetic admixture within populations of migrating fish species.[4] Genetic admixture may have an important role for the success of populations that colonise a new area and interbreed with individuals of native populations.[5]

Mapping

Admixture mapping is a method of gene mapping that uses a population of mixed ancestry (an admixed population) to find the genetic loci that contribute to differences in diseases or other phenotypes found between the different ancestral populations. The method is best applied to populations with recent admixture from two populations that were previously genetically isolated for tens of thousands of years, such as African Americans and European Americans (admixture of African and European populations). The method attempts to correlate the degree of ancestry near a genetic locus with the phenotype or disease of interest. Genetic markers that differ in frequency between the ancestral populations are needed across the genome.[6]

Admixture mapping is based on the assumption that differences in disease rates or phenotypes are due in part to differences in the frequencies of disease-causing or phenotype-causing genetic variants between populations. In an admixed population, these causal variants occur more frequently on chromosomal segments inherited from one or another ancestral population. The first admixture scans were published in 2005 and since then genetic contributors to a variety of disease and trait differences have been mapped.[7] These include hypertension, multiple sclerosis, BMI, and prostate cancer in African Americans. By 2010, high-density mapping panels had been constructed for African Americans, Latino/Hispanics, and Uyghurs.

See also

References
  1. Rius, M. and Darling, J.A. (2014). "How important is intraspecific genetic admixture to the success of colonising populations?". Trends in Ecology & Evolution. 29 (4): 233−242. doi:10.1016/j.tree.2014.02.003. PMID 24636862.CS1 maint: uses authors parameter (link)
  2. Yang, Melinda A.; Fu, Qiaomei (March 2018). "Insights into Modern Human Prehistory Using Ancient Genomes". Trends in Genetics. 34 (3): 184–196. doi:10.1016/j.tig.2017.11.008. PMID 29395378.
  3. Lv, X., Cheng, J., Meng, Y., Chang, Y., Xia, L., Wen, Z., Ge, D., Liu, S. and Yang, Q. (2018). "Disjunct distribution and distinct intraspecific diversification of Eothenomys melanogaster in South China". BMC Evolutionary Biology. 18 (1): 50. doi:10.1186/s12862-018-1168-3. PMC 5894153. PMID 29636000.CS1 maint: uses authors parameter (link)
  4. Jaisuk, C. and Senanan, W. (2018). "Effects of landscape features on population genetic variation of a tropical stream fish, Stone lapping minnow, Garra cambodgiensis, in the upper Nan River drainage basin, northern Thailand". PeerJ. 6: e4487. doi:10.7717/peerj.4487. PMC 5845392. PMID 29568710.CS1 maint: uses authors parameter (link)
  5. Kolbe, J.J., Larson, A., Losos, J.B. and de Queiroz, K. (2008). "Admixture determines genetic diversity and population differentiation in the biological invasion of a lizard species". Biology Letters. 4 (4): 434−437. doi:10.1098/rsbl.2008.0205. PMC 2610154. PMID 18492644.CS1 maint: uses authors parameter (link)
  6. Shriver, MD; et al. (April 2003). "Skin pigmentation, biogeographical ancestry and admixture mapping". Human Genetics. 112 (4): 387–99. doi:10.1007/s00439-002-0896-y. PMID 12579416.
  7. Winkler, C. A.; Nelson, G. W.; Smith, M. W. (2010). "Admixture mapping comes of age". Annu Rev Genom Hum Genet. 11: 65–89. doi:10.1146/annurev-genom-082509-141523. PMID 20594047.

Further reading
  • Balding (2007). "Glossary of Genetic Terms". Handbook of statistical genetics, Volume 1. ISBN 978-0-470-05830-5.
  • Foulkes (28 April 2009). "Glossary of Terms". Applied Statistical Genetics With R: For Population-based Association Studies. p. 250. ISBN 978-0-387-89553-6.
  • Stone; et al. (2007). "Glossary of Terms". Genes, culture, and human evolution: a synthesis. ISBN 978-1-4051-5089-7.
  • Kolbe JJ, Glor RE, Schettino LR, Lara AC, Losos AL, Losos JB (2004) Genetic Variation Increases during Biological Invasion by a Cuban Lizard. Nature 431: 171-181
  • Lenormand T (2002). Gene flow and the limits to natural selection. Trends in Ecology and Evolution. 17:183-189
  • Shriner 2013, "Overview of Admixture Mapping"
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