what is allele frequency

Allele frequency, also known as gene frequency, refers to 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. Allele frequency is calculated by dividing the number of times the allele of interest is observed in a population by the total number of copies of all the alleles at that particular genetic locus in the population. Allele frequencies can be represented as a decimal, a percentage, or a fraction. In population genetics, allele frequencies are used to describe the amount of variation at a particular locus or across multiple loci. The frequency of an allele is distinct from the genotype frequency, although they are related, and allele frequencies can be calculated from genotype frequencies. The frequencies of all the alleles of a gene must add up to one, or 100% . Changes in allele frequencies over time can indicate that genetic drift is occurring or that new mutations have been introduced into the population.