🧬 Allele Frequency Calculator
Calculate allele frequencies from genotype counts
How to Use This Calculator
Enter Genotype Counts
Input the number of homozygous dominant (AA), heterozygous (Aa), and homozygous recessive (aa) individuals in your population.
Calculate Allele Frequencies
Click "Calculate Allele Frequencies" to see allele frequencies (p and q), observed and expected genotype frequencies, and Hardy-Weinberg equilibrium test results.
Review Results
Review allele frequencies (p and q), observed vs. expected genotype frequencies, and chi-square test results for Hardy-Weinberg equilibrium.
Interpret Results
Use allele frequencies for population genetics analysis. Chi-square test (χ² < 3.841) suggests Hardy-Weinberg equilibrium. Values ≥ 3.841 suggest evolutionary forces are acting.
Formula
p = (2×AA + Aa) / (2×total)
q = (2×aa + Aa) / (2×total)
p + q = 1
Expected: p² = AA, 2pq = Aa, q² = aa
Example: AA=360, Aa=480, aa=160, Total=1000
Step 1: Calculate p (allele A frequency)
p = (2×360 + 480) / (2×1000) = (720 + 480) / 2000 = 1200/2000 = 0.6
Step 2: Calculate q (allele a frequency)
q = (2×160 + 480) / (2×1000) = (320 + 480) / 2000 = 800/2000 = 0.4
Step 3: Verify p + q = 1
p + q = 0.6 + 0.4 = 1.0 ✓
Step 4: Expected genotype frequencies (Hardy-Weinberg)
Expected AA = p² = 0.6² = 0.36 (360 individuals)
Expected Aa = 2pq = 2×0.6×0.4 = 0.48 (480 individuals)
Expected aa = q² = 0.4² = 0.16 (160 individuals)
Since observed = expected, χ² = 0 → In equilibrium
About Allele Frequency Calculator
The Allele Frequency Calculator is an essential tool for genetics students, researchers, and biologists who need to calculate allele frequencies from genotype counts in populations. This calculator implements standard population genetics formulas to determine allele frequencies (p and q), expected genotype frequencies, and tests for Hardy-Weinberg equilibrium.
When to Use This Calculator
- Population Genetics: Calculate allele frequencies from genotype counts in populations
- Equilibrium Testing: Test if a population is in Hardy-Weinberg equilibrium
- Genetic Research: Analyze population genetic data and allele frequencies
- Evolutionary Studies: Study changes in allele frequencies over time
- Educational Use: Learn and understand allele frequency calculations
Why Use Our Calculator?
- ✅ Accurate Formulas: Uses standard allele frequency calculation formulas
- ✅ Equilibrium Testing: Automatically tests for Hardy-Weinberg equilibrium using chi-square
- ✅ Complete Analysis: Shows observed and expected genotype frequencies
- ✅ Easy to Use: Simple inputs for genotype counts
- ✅ Time Savings: Instant calculations eliminate manual math
Understanding Allele Frequencies
Basic Principle: Allele frequency (p and q) represents the proportion of a specific allele in a population. For a two-allele system, p + q = 1, where p is the frequency of allele A and q is the frequency of allele a. Allele frequencies are calculated from genotype counts using the formulas: p = (2×AA + Aa) / (2×total) and q = (2×aa + Aa) / (2×total).
Hardy-Weinberg Equilibrium: Under Hardy-Weinberg equilibrium, expected genotype frequencies are p² for AA, 2pq for Aa, and q² for aa. If observed frequencies match expected frequencies (χ² < 3.841), the population is in equilibrium. If not (χ² ≥ 3.841), evolutionary forces are acting on the population.
Applications: Allele frequencies are used in population genetics to study genetic variation, predict genotype frequencies, test for evolutionary forces, and analyze population genetic data.
Tips for Best Results
- Accurate Counts: Ensure genotype counts are accurate for reliable allele frequency calculations
- Large Populations: Allele frequencies are most accurate in large populations
- Verify p + q = 1: Allele frequencies must sum to 1 (or very close to 1)
- Chi-Square Interpretation: χ² < 3.841 suggests equilibrium (1 degree of freedom, p=0.05)
- Understand Limitations: Real populations rarely maintain perfect Hardy-Weinberg equilibrium
Frequently Asked Questions
What is allele frequency?
Allele frequency (p and q) represents the proportion of a specific allele in a population. For a two-allele system, p is the frequency of allele A and q is the frequency of allele a, and p + q = 1. Allele frequencies range from 0 to 1 and sum to 1.
How do I calculate allele frequency from genotype counts?
Use the formulas: p = (2×AA + Aa) / (2×total) and q = (2×aa + Aa) / (2×total). For example, with AA=360, Aa=480, aa=160, total=1000: p = (720+480)/2000 = 0.6, q = (320+480)/2000 = 0.4. The calculator does this automatically.
What does Hardy-Weinberg equilibrium mean?
Hardy-Weinberg equilibrium occurs when observed genotype frequencies match expected frequencies (p², 2pq, q²). If χ² < 3.841, the population is in equilibrium, suggesting no evolutionary forces. If χ² ≥ 3.841, evolutionary forces (mutation, migration, selection, drift, non-random mating) are acting.
Why do p and q must equal 1?
In a two-allele system, p + q = 1 because all alleles in the population must be either A or a. There are no other alleles, so the frequencies must sum to 1 (100%). If p + q ≠1, there may be an error in genotype counts or calculations.
What if my population is not in Hardy-Weinberg equilibrium?
If a population is not in Hardy-Weinberg equilibrium (χ² ≥ 3.841), it suggests evolutionary forces are acting: mutation, migration, selection, genetic drift, or non-random mating. This is normal for real populations—perfect equilibrium is rare. The deviation indicates active evolutionary processes.