🧬 Hardy-Weinberg Calculator
Calculate allele and genotype frequencies in populations
Frequency of dominant allele A (0-1)
Frequency of recessive allele a (0-1), should equal 1-p
Enter to calculate expected genotype counts
How to Use This Calculator
Select Calculation Type
Choose whether you have allele frequencies (p and q) or genotype counts (AA, Aa, aa).
Enter Values
If using allele frequencies, enter p (frequency of A) and q (frequency of a). If using genotype counts, enter the number of AA, Aa, and aa individuals.
Optional: Enter Population Size
If calculating from allele frequencies, optionally enter population size to calculate expected genotype counts.
Calculate and Review
Click "Calculate" to see genotype frequencies, allele frequencies, expected counts, and Hardy-Weinberg equilibrium test results.
Formula
p + q = 1
p² + 2pq + q² = 1
where: p² = AA, 2pq = Aa, q² = aa
p = (2×AA + Aa) / (2×total), q = (2×aa + Aa) / (2×total)
Example 1: From allele frequencies (p = 0.6, q = 0.4)
Step 1: p² = 0.6² = 0.36 (36% AA)
Step 2: 2pq = 2 × 0.6 × 0.4 = 0.48 (48% Aa)
Step 3: q² = 0.4² = 0.16 (16% aa)
Step 4: Total = 0.36 + 0.48 + 0.16 = 1.00 ✓
Example 2: From genotype counts (AA=360, Aa=480, aa=160, Total=1000)
Step 1: p = (2×360 + 480) / (2×1000) = 1200/2000 = 0.6
Step 2: q = (2×160 + 480) / (2×1000) = 800/2000 = 0.4
Step 3: Expected AA = 0.6² × 1000 = 360
Step 4: Expected Aa = 2×0.6×0.4 × 1000 = 480
Step 5: Expected aa = 0.4² × 1000 = 160
Step 6: χ² = 0 (observed = expected) → In equilibrium
About Hardy-Weinberg Calculator
The Hardy-Weinberg Calculator is an essential tool for genetics students, researchers, and biologists who need to calculate allele and genotype frequencies in populations. This calculator implements the Hardy-Weinberg equilibrium principle, which describes how allele and genotype frequencies remain constant in a population from generation to generation in the absence of evolutionary influences.
When to Use This Calculator
- Population Genetics: Calculate allele and genotype frequencies in populations
- Equilibrium Testing: Test if a population is in Hardy-Weinberg equilibrium
- Predictive Analysis: Predict expected genotype frequencies from allele frequencies
- Genetic Research: Analyze population genetic data
- Educational Use: Learn and understand Hardy-Weinberg equilibrium principles
Why Use Our Calculator?
- ✅ Dual Calculation Modes: Calculate from allele frequencies or genotype counts
- ✅ Equilibrium Testing: Automatically tests for Hardy-Weinberg equilibrium using chi-square
- ✅ Expected Counts: Calculates expected genotype counts for given population size
- ✅ Accurate Formulas: Uses standard Hardy-Weinberg equilibrium equations
- ✅ Time Savings: Instant calculations eliminate manual math
Understanding Hardy-Weinberg Equilibrium
Basic Principle: The Hardy-Weinberg equilibrium states that allele and genotype frequencies in a population remain constant from generation to generation in the absence of evolutionary influences (mutation, migration, selection, genetic drift, non-random mating). The principle is expressed as p² + 2pq + q² = 1, where p and q are allele frequencies.
Assumptions: For Hardy-Weinberg equilibrium to hold, the population must be large, have random mating, no mutations, no migration, no selection, and no genetic drift. Real populations rarely meet all these conditions, making the equilibrium a theoretical baseline.
Applications: The Hardy-Weinberg principle is used in population genetics to test for evolutionary forces, predict genotype frequencies, estimate allele frequencies, and study genetic variation in populations.
Tips for Best Results
- Verify p + q = 1: Allele frequencies must sum to 1 (or very close to 1)
- Accurate Counts: Ensure genotype counts are accurate for reliable equilibrium testing
- Large Populations: Hardy-Weinberg applies best to large populations
- Chi-Square Interpretation: χ² < 3.841 suggests equilibrium (1 degree of freedom, p=0.05)
- Understand Limitations: Real populations rarely maintain perfect equilibrium
Frequently Asked Questions
What is Hardy-Weinberg equilibrium?
Hardy-Weinberg equilibrium is a principle in population genetics stating that allele and genotype frequencies remain constant from generation to generation in the absence of evolutionary influences. It's expressed as p² + 2pq + q² = 1, where p and q are allele frequencies.
How do I calculate genotype frequencies from allele frequencies?
Use the formulas: p² for homozygous dominant (AA), 2pq for heterozygous (Aa), and q² for homozygous recessive (aa). For example, if p=0.6 and q=0.4, then AA = 0.36, Aa = 0.48, and aa = 0.16.
How do I calculate allele frequencies 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.
What does it mean if a 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 on the population: mutation, migration, selection, genetic drift, or non-random mating. This is normal for real populations.
What assumptions does Hardy-Weinberg equilibrium require?
Hardy-Weinberg equilibrium requires: large population size, random mating, no mutations, no migration, no selection, and no genetic drift. These assumptions are rarely all met in real populations, making equilibrium a theoretical baseline.