Allele Frequency Calculator
Find allele frequencies from allele counts.
Calculate the frequency of two alleles in a population.
How the Math Works
The Allele Frequency Calculator uses a fundamental principle of genetics: in a population at equilibrium, the frequencies of all alleles must sum to 1. For a gene with two alleles (A and a), we first calculate the frequency of allele A (denoted as p) by dividing its count by the total number of alleles (A + a). The frequency of allele a (q) is then simply 1 minus p, ensuring p + q = 1. This follows the Hardy-Weinberg principle, which states that allele frequencies remain constant across generations in the absence of evolutionary forces.
Practical Applications
To use this calculator, count how many times each allele appears in your sample (for diploid organisms, count both copies in each individual). Enter the count for allele A and allele a into the calculator. It will automatically compute p by dividing the A count by the total, and q by subtracting p from 1. For example, if you observe 150 A alleles and 50 a alleles in a population, p = 150/200 = 0.75 and q = 1 - 0.75 = 0.25. This calculation is essential for genetic research, breeding programs, and population genetics studies.
Day-to-Day Use
Understanding allele frequencies helps explain why certain genetic traits become more or less common in populations over time. For instance, if you're involved in agriculture, knowing allele frequencies can guide breeding decisions to develop crops with desirable traits like disease resistance or improved yield. In medicine, this knowledge helps assess how common genetic variants are that may affect drug metabolism or disease susceptibility in different populations. Even in ancestry testing, allele frequency comparisons across global populations help explain patterns of human genetic diversity and migration.
Worked example
60 A, 40 a → p = 0.6, q = 0.4.
FAQ
From genotypes?
Each individual carries two alleles; count them across all individuals.