Genetic admixture

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Genetic admixture occurs when two or more previously isolated and genetically differentiated populations begin interbreeding.[1] 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.[2] Natural flooding can cause genetic admixture within populations of migrating fish species.[3] Genetic admixture may have an important role for the success of populations that colonise a new area and interbreed with individuals of native populations.[4]

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 (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.[5]

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.[6] 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

Notes

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. 
  2. ^ 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. 
  3. ^ 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. 
  4. ^ 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. 
  5. ^ Shriver MD, Mark D, et al. 2003. Skin Pigmentation, biogeographical ancestry and admixture mapping. Hum. Genet. 112, 387-399 (2003)
  6. ^ 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 0-470-05830-7. 
  • Foulkes. "Glossary of Terms". Applied Statistical Genetics With R: For Population-based Association Studies. p. 250. ISBN 0-387-89553-1. 
  • Stone; et al. (2007). "Glossary of Terms". Genes, culture, and human evolution: a synthesis. ISBN 1-4051-5089-0. 
  • 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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