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An allele [1] (or allelomorph) is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule. [2]Alleles can differ at a single position through single nucleotide polymorphisms (SNP), [3] but they can also have insertions and deletions of up to several thousand base pairs.
If (), (), and () are the frequencies of the three genotypes at a locus with two alleles, then the frequency p of the A-allele and the frequency q of the B-allele in the population are obtained by counting alleles. [2]
Population structure (also called genetic structure and population stratification) is the presence of a systematic difference in allele frequencies between subpopulations.In a randomly mating (or panmictic) population, allele frequencies are expected to be roughly similar between groups.
In other words, if the allele frequency of A equals 70%, the remaining 30% of the alleles must be a, because together they equal 100%. [5] For a gene that exists in two alleles, the Hardy–Weinberg equation states that (p 2) + (2pq) + (q 2) = 1. If we apply this equation to our flower color gene, then
Disruptive selection favors both extreme phenotypes while the moderate phenotype will be selected against. The frequency of both extreme alleles will increase while the frequency of the moderate allele will decrease, differing from the trend in directional selection in which only one extreme allele is favored.
Gene flow is the transfer of alleles from one population to another population through immigration of individuals. In population genetics, gene flow (also known as migration and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent ...
Nevertheless, the concept is still widely used in evolutionary genetics, e.g. to explain the persistence of deleterious alleles as in the case of spinal muscular atrophy, [5] [4] or, in theoretical models, mutation-selection balance can appear in a variety of ways and has even been applied to beneficial mutations (i.e. balance between selective ...
Fixed alleles were first defined by Motoo Kimura in 1962. [5] Kimura discussed how fixed alleles could arise within populations and was the first to generalize the topic. He credits the works of Haldane in 1927 [ 6 ] and Fisher in 1922 [ 7 ] as being important in providing foundational information that allowed him to come to his conclusion.