What is allele frequency?
Allele frequency (or gene frequency) represents the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. In simpler terms, it shows how common a specific trait or gene variant is within a group of organisms sharing a common gene pool.
Hardy-Weinberg equilibrium context
In population genetics, allele frequencies are heavily utilized to check if a population is evolving. According to the Hardy-Weinberg Principle, in the absence of evolutionary influences (like natural selection, mutations, or genetic drift), allele frequencies will remain constant from generation to generation.
By Convention, we denote the dominant allele frequency as p and the recessive allele frequency as q. Under perfectly stable conditions, p + q = 1.
How to calculate allele frequency
If you know the phenotypic or genotypic counts for a given trait in your population, calculating the underlying allele mathematical frequencies is straightforward.
- Count the number of Homozygous Dominant individuals (AA)
- Count the number of Heterozygous individuals (Aa)
- Count the number of Homozygous Recessive individuals (aa)
Input these raw population numbers into our calculator to dynamically generate precise p and q frequencies.
Allele frequency formula
Because standard diploid organisms carry two copies of each gene (two alleles), the total number of alleles is exactly twice the number of individuals measured.
p = [ (2 × AA) + Aa ] / (2 × Total Population)
q = [ (2 × aa) + Aa ] / (2 × Total Population)