Hardy-Weinberg q²
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The Hardy-Weinberg q² calculator determines the frequency of the homozygous recessive genotype (aa) in a population using the formula q². This equation is part of the Hardy-Weinberg principle, which models allele and genotype distributions in populations under genetic equilibrium.
To use the calculator, input the frequency of the recessive allele (q). The result will show the expected proportion of individuals with the aa genotype. This is useful for population genetics studies, such as predicting recessive disease prevalence.
The calculation assumes no mutation, migration, natural selection, or other evolutionary forces. In real populations, factors like small size or non-random mating may invalidate results.
Practical example: if q = 0.3 (30% recessive alleles), the aa frequency is 0.09 (9%). This helps assess whether a genetic disorder aligns with Hardy-Weinberg expectations.
Frequently asked questions
What does the q² value represent in population genetics?
The q² value represents the frequency of the homozygous recessive genotype (aa) in a population under Hardy-Weinberg equilibrium.
Why must the population be in equilibrium to use this calculator?
Hardy-Weinberg equilibrium is required to ensure genotype frequencies are calculated accurately, without evolutionary pressures like selection or mutation.
How to convert the recessive allele frequency to a decimal?
If 30% of alleles are recessive, input q = 0.3 (or 30%). The calculator automatically converts and applies the q² formula.
Is there a limit for the q value?
No, as long as 0 ≤ q ≤ 1. Values outside this range are invalid in population genetics.
Can this calculator be used for recessive diseases?
Yes, it's particularly useful for predicting recessive disease frequencies in populations under ideal equilibrium conditions.