In natural selection, negative selection[1] or purifying selection is the selective removal of alleles that are deleterious. This can result in stabilising selection through the purging of deleterious genetic polymorphisms that arise through random mutations.[2][3]
Purging of deleterious alleles can be achieved on the population genetics level, with as little as a single point mutation being the unit of selection. In such a case, carriers of the harmful point mutation have fewer offspring each generation, reducing the frequency of the mutation in the gene pool.
In the case of strong negative selection on a locus, the purging of deleterious variants will result in the occasional removal of linked variation, producing a decrease in the level of variation surrounding the locus under selection. The incidental purging of non-deleterious alleles due to such spatial proximity to deleterious alleles is called background selection.[4] This effect increases with lower mutation rate but decreases with higher recombination rate.[5]
Purifying selection can be split into purging by non-random mating (assortative mating) and purging by genetic drift. Purging by genetic drift can remove primarily deeply recessive alleles, whereas natural selection can remove any type of deleterious alleles.[6]
Negative selection in haploid compared to diploid tissue
editThe idea that those genes of an organism that are expressed in the haploid stage are under more efficient natural selection than those genes expressed exclusively in the diploid stage is referred to as the “masking theory”.[7] This theory implies that purifying selection is more efficient in the haploid stage of the life cycle where fitness effects are more fully expressed than in the diploid stage of the life cycle. Evidence supporting the masking theory has been reported in the single-celled yeast Saccharomyces cerevisiae.[8] Further evidence of strong purifying selection in haploid tissue-specific genes, in support of the masking theory, has been reported for the plant, Scots Pine.[7]
See also
editReferences
edit- ^ Loewe L (2008). "Negative selection". Nature Education. 1 (1): 59.
- ^ Tien NS, Sabelis MW, Egas M (March 2015). "Inbreeding depression and purging in a haplodiploid: gender-related effects". Heredity. 114 (3): 327–32. doi:10.1038/hdy.2014.106. PMC 4815584. PMID 25407077.
- ^ Gulisija D, Crow JF (May 2007). "Inferring purging from pedigree data". Evolution; International Journal of Organic Evolution. 61 (5): 1043–51. doi:10.1111/j.1558-5646.2007.00088.x. PMID 17492959. S2CID 24302475.
- ^ Charlesworth B, Morgan MT, Charlesworth D (August 1993). "The effect of deleterious mutations on neutral molecular variation". Genetics. 134 (4): 1289–303. doi:10.1093/genetics/134.4.1289. PMC 1205596. PMID 8375663.
- ^ Hudson RR, Kaplan NL (December 1995). "Deleterious background selection with recombination". Genetics. 141 (4): 1605–17. doi:10.1093/genetics/141.4.1605. PMC 1206891. PMID 8601498.
- ^ Glémin S (December 2003). "How are deleterious mutations purged? Drift versus nonrandom mating". Evolution; International Journal of Organic Evolution. 57 (12): 2678–87. doi:10.1111/j.0014-3820.2003.tb01512.x. PMID 14761049.
- ^ a b Cervantes S, Kesälahti R, Kumpula TA, Mattila TM, Helanterä H, Pyhäjärvi T (August 2023). "Strong Purifying Selection in Haploid Tissue-Specific Genes of Scots Pine Supports the Masking Theory". Mol Biol Evol. 40 (8). doi:10.1093/molbev/msad183. PMC 10457172. PMID 37565532.
- ^ Gerstein AC, Cleathero LA, Mandegar MA, Otto SP (March 2011). "Haploids adapt faster than diploids across a range of environments". J Evol Biol. 24 (3): 531–40. doi:10.1111/j.1420-9101.2010.02188.x. PMID 21159002.
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