Allele Frequency Calculator
Determine the frequency of dominant and recessive alleles within a population. Enter the observed count of homozygous dominant, heterozygous, and homozygous recessive genotypes.
Genotype Counts
Input the number of individuals observed for each genotype.
Allele Frequencies
Expert Tip
By definition, the sum of allele frequencies $p + q$ must always equal exactly $1.0$. If the population is in Hardy-Weinberg equilibrium, the expected genotype frequencies will match $p^2$, $2pq$, and $q^2$.
Methodology & Equations
Allele Frequency Math
In diploid organisms, each individual carries two alleles per gene. The allele frequencies ($p$ for dominant allele $A$ and $q$ for recessive allele $a$) are calculated as:
Genotypic Frequencies
Genotypic frequency is the proportion of a specific genotype in the population:
- f(AA) = observed Homozygous Dominant / Total Population
- f(Aa) = observed Heterozygous / Total Population
- f(aa) = observed Homozygous Recessive / Total Population
How to Calculate Allele Frequencies: Step-by-Step
Allele frequency calculations show how common a specific variant of a gene (an allele) is within a population. Below is a practical step-by-step example:
Determine the Total Allele Pool
Because every diploid organism carries 2 alleles for each gene, multiply the total population size (N) by 2. For example, if your population has 100 individuals, the total allele pool size is 200 alleles.
Count the Target Alleles
To find the count of dominant alleles (A), count 2 for every homozygous dominant individual (AA) and 1 for every heterozygous individual (Aa).
Formula: Count(A) = (2 × N_AA) + N_Aa
Divide by the Total Allele Pool
Divide your allele count by the total allele pool to get the frequency.
Formula: p = Count(A) / (2 × N)
Related Calculators
View All Biology Tools →Hardy-Weinberg Equilibrium
Calculate expected genotype frequencies and test for equilibrium.
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Predict genotypic and phenotypic ratios of offspring for a single gene.
Punnett Square Calculator
Generate 2x2 Punnett squares and calculate genotypic probabilities.