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
Sum of Alleles Rule
The sum of allele frequencies p + q must always equal 1.0 (100%).
Allele Frequency & Population Pool Reference Table
| Population Size (N) | Total Alleles (2N) | AA / Aa / aa Counts | p (Freq A) | q (Freq a) |
|---|---|---|---|---|
| 100 | 200 | 64 / 32 / 4 | 0.800 | 0.200 |
| 100 | 200 | 49 / 42 / 9 | 0.700 | 0.300 |
| 100 | 200 | 25 / 50 / 25 | 0.500 | 0.500 |
| 500 | 1,000 | 45 / 210 / 245 | 0.300 | 0.700 |
Calculation Methodology & Biological Principles
Allele Frequency Formulas
The factor of 2 accounts for diploid organisms carrying two alleles per locus.
Gene Pool Concepts
Allele frequencies measure microevolutionary shifts. Changes in p or q over time indicate active evolutionary forces such as genetic drift, natural selection, or migration.
Frequently Asked Questions
What is Allele Frequency? ▼
Allele frequency (gene frequency) represents the relative proportion of a specific gene variant (allele) at a locus in a population, expressed as a decimal or percentage.
How do you calculate p and q from genotype counts? ▼
For a diploid population with genotypes AA, Aa, and aa: p = (2*N_AA + N_Aa) / (2*N_total) and q = (2*N_aa + N_Aa) / (2*N_total), where p + q = 1.
Why does the allele pool size equal 2 * N? ▼
Diploid organisms carry two copies (alleles) of each somatic gene locus—one inherited from the mother and one from the father. Thus, a population of N individuals contains 2*N total alleles in its gene pool.
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