Balancing selection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone. Balancing selection is rare compared to purifying selection.[1] It can occur by various mechanisms, in particular, when the heterozygotes for the alleles under consideration have a higher fitness than the homozygote.[2] In this way genetic polymorphism is conserved.[3]
Evidence for balancing selection can be found in the number of alleles in a population which are maintained above mutation rate frequencies. All modern research has shown that this significant genetic variation is ubiquitous in panmictic populations.
There are several mechanisms (which are not exclusive within any given population) by which balancing selection works to maintain polymorphism. The two major and most studied are heterozygote advantage and frequency-dependent selection.
^Charlesworth, Deborah; Willis, John H. (November 2009). "The genetics of inbreeding depression". Nature Reviews Genetics. 10 (11): 783–796. doi:10.1038/nrg2664. ISSN 1471-0064. PMID 19834483. S2CID 771357.
^King, R.C.; Stansfield, W.D.; Mulligan, P.K. (2006). A dictionary of genetics (7th ed.). Oxford: Oxford University Press. p. 44.
^Ford, E.B. (1940). "Polymorphism and taxonomy". In J. Huxley (ed.). The New Systematics. Oxford: Clarendon Press. pp. 493–513.
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Balancingselection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the...
years or exists as a selective by-product. The balancingselection hypothesis suggests that balancingselection, an evolutionary mechanism, has allowed for...
bimodal distribution of trait values. Finally, balancingselection can occur through frequency-dependent selection, where the fitness of one particular phenotype...
United States. Balancingselection may act upon ospC or a nearby sequence to maintain the genetic variety of B. burgdorferi. Balancingselection is the process...
HLA-B HLA-DRB1 loci alone. Some polymorphism may be maintained by balancingselection. A rule of thumb that is sometimes used is to classify genetic variants...
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gene remains in two species, likely due to strong pathogen-mediated balancingselection by pathogens that can infect both species. Birth-and-death evolution...
Beck, Jonathan A.; Poulter, Mark; Campbell, Tracy; et al. (2003). "Balancingselection at the prion protein gene consistent with prehistoric kurulike epidemics"...
Emerson JJ, Cardoso-Moreira M, Borevitz JO, Long M (June 2008). "Natural selection shapes genome-wide patterns of copy-number polymorphism in Drosophila...
pp. 82–116. Mead S, Stumpf MP, Whitfield J, et al. (April 2003). "Balancingselection at the prion protein gene consistent with prehistoric kurulike epidemics"...
population size, but by any factor that affects evolvability, including balancingselection, cryptic genetic variation, phenotypic plasticity, and robustness...
biologists for explanation. Most posit balancingselection (see polymorphism (biology)), which is any natural selection process whereby no single allele is...
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majority of human loci. This is consistent with a heterozygous or balancingselection coefficient for these loci. In addition, some HLA loci are among...
continued presence of the O alleles is hypothesized to be the result of balancingselection. Both theories contradict the previously held theory that type O...
Unckless RL, Howick VM, Lazzaro BP (January 2016). "Convergent BalancingSelection on an Antimicrobial Peptide in Drosophila". Current Biology. 26 (2):...
alleles to approach fixation. Disassortative mating may result in balancingselection and the maintenance of high genetic variation in the population....
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