Genotype Frequency Calculator

In genetics, a genotype is the specific combination of alleles an organism carries for a given trait — and the Genotype Frequency Calculator tells you how common each combination is within a population. Select your calculation method: enter allele frequencies (p and q) directly, or input observed genotype counts (AA, Aa, aa) along with total population size. The calculator returns the frequency of each genotype — AA (homozygous dominant), Aa (heterozygous), and aa (homozygous recessive) — plus the derived allele frequencies p and q.

Results

AA Genotype Frequency

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Aa Genotype Frequency

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aa Genotype Frequency

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Allele A Frequency (p)

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Allele a Frequency (q)

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Total Population

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Frequently Asked Questions

What is the Hardy-Weinberg equilibrium principle?

Hardy-Weinberg equilibrium states that allele and genotype frequencies remain constant in a population from generation to generation, provided certain conditions are met (no mutations, no selection, no migration, large population size, and random mating).

How do you calculate genotype frequencies from allele frequencies?

If p is the frequency of allele A and q is the frequency of allele a, then the genotype frequencies are: AA = p², Aa = 2pq, and aa = q². Remember that p + q = 1.

What does it mean if p + q doesn't equal 1?

If p + q doesn't equal 1, there may be an error in your data entry or the population may have more than two alleles at this locus. In a two-allele system, the frequencies must sum to 1.

How do you calculate allele frequencies from genotype counts?

To find p: count all A alleles (2×AA + Aa) and divide by total alleles (2×N). To find q: count all a alleles (2×aa + Aa) and divide by total alleles (2×N), where N is the total number of individuals.

What is the difference between homozygous and heterozygous genotypes?

Homozygous genotypes have two identical alleles (AA or aa), while heterozygous genotypes have two different alleles (Aa). Homozygous dominant is AA, homozygous recessive is aa.

Can this calculator be used for populations not in Hardy-Weinberg equilibrium?

This calculator shows expected frequencies under Hardy-Weinberg conditions. Real populations may deviate due to factors like inbreeding, population structure, or natural selection, but it provides a useful baseline for comparison.

What sample size is needed for accurate genotype frequency calculations?

Larger sample sizes provide more accurate estimates. Generally, you want at least 30-50 individuals for basic calculations, though hundreds or thousands give more reliable results for population genetics studies.

How do you interpret the calculated frequencies?

Frequencies range from 0 to 1, where 1 means 100% of the population has that genotype. The three genotype frequencies (AA, Aa, aa) should always sum to 1.0 in a complete analysis.