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Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. Specifically, it is the fraction of all chromosomes in the population that carry that allele. Given the following: # a particular locus on a chromosome and a given allele at that locus # a population of ''N'' individuals with ploidy ''n'', i.e. an individual carries ''n'' copies of each chromosome in their somatic cells (e.g. two chromosomes in the cells of diploid species) # the allele exists in ''i'' chromosomes in the population then the allele frequency is the fraction of all the occurrences ''i'' of that allele and the total number of chromosome copies across the population, ''i/(nN)''. For a diploid population, this fraction is ''i/(2N)''. The allele frequency is distinct from the genotype frequency, although they are related, and allele frequencies can be calculated from genotype frequencies.〔 In population genetics, allele frequencies are used to describe the amount of variation at a particular locus or across multiple loci. When considering the ensemble of allele frequencies for a large number of distinct loci, their distribution is called the allele frequency spectrum. == Calculation of allele frequencies from genotype frequencies== The actual frequency calculations depend on the ploidy of the species for autosomal genes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Allele frequency」の詳細全文を読む スポンサード リンク
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