Allele Frequency Calculator

In genetics, allele frequency measures how common a gene variant is within a population — a key calculation in evolutionary biology, population genetics, and Hardy-Weinberg analysis. Enter your population data using genotype counts (AA, Aa, aa), phenotype counts, or genotype percentages into the Allele Frequency Calculator to find the frequency of p (dominant allele) and frequency of q (recessive allele). Secondary outputs include total population size and the Hardy-Weinberg expected counts for each genotype.

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Results

Frequency of p (dominant allele)

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Frequency of q (recessive allele)

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Total population size

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Hardy-Weinberg AA expected

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Hardy-Weinberg Aa expected

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Hardy-Weinberg aa expected

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Results Table

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Frequently Asked Questions

What is allele frequency?

Allele frequency is the relative proportion of a specific allele (gene variant) in a population. It's expressed as a decimal between 0 and 1, where p represents the frequency of the dominant allele and q represents the frequency of the recessive allele.

How do you calculate P and Q allele frequency?

From genotype counts: p = (2×AA + Aa) / (2×N) and q = (2×aa + Aa) / (2×N), where N is total population. From phenotype data with Hardy-Weinberg assumption: q = √(recessive frequency) and p = 1 - q.

What is the Hardy-Weinberg equation?

The Hardy-Weinberg equation is p² + 2pq + q² = 1, where p² represents AA frequency, 2pq represents Aa frequency, and q² represents aa frequency. This equation predicts genotype frequencies in populations that are not evolving.

What do P and Q mean in allele frequency?

P represents the frequency of the dominant allele in a population, while Q represents the frequency of the recessive allele. Since these are the only two alleles for a given gene, p + q always equals 1.

How to calculate minor allele frequency?

Minor allele frequency (MAF) is the frequency of the less common allele in a population. Calculate both p and q, then the MAF is whichever value is smaller. MAF is important in genetics research and disease association studies.

When can I use Hardy-Weinberg equilibrium assumptions?

Hardy-Weinberg equilibrium applies when there's no mutation, migration, selection, or non-random mating, and the population is large. While real populations rarely meet all conditions perfectly, it provides a useful baseline for comparison.

What's the difference between genotype and phenotype frequency calculations?

Genotype frequency uses actual counts of AA, Aa, and aa individuals to directly calculate allele frequencies. Phenotype frequency uses observable traits (dominant vs recessive) and requires Hardy-Weinberg assumptions to estimate underlying genotype frequencies.