What is the allele frequency?

Allele frequency is a measure of the relative frequency of an allele on a genetic locus in a population.

Usually it is expressed as a proportion or a percentage.

In population genetics, allele frequencies show the genetic diversity of a species population or equivalently the richness of its gene pool.

The frequencies of all the alleles of a given gene often are graphed together as an allele frequency distribution histogram.

Population genetics studies the different "forces" that might lead to changes in the distribution and frequencies of alleles - in other words, to evolution.

Besides selection, these forces include genetic drift, mutation and migration.