Hardy-Weinberg Equilibrium Calculator

Category: Biology
- March 22, 2025
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Calculate genotype and allele frequencies using the Hardy-Weinberg principle (p² + 2pq + q² = 1).

Input Type

Genotype Counts

Display Options

About Hardy-Weinberg Equilibrium

The Hardy-Weinberg principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.

The Hardy-Weinberg Equation

For a genetic locus with two alleles (A and a) with frequencies p and q respectively:

  • p + q = 1 (allele frequencies sum to 1)
  • p² + 2pq + q² = 1 (genotype frequencies sum to 1)
  • Where:
    • p² = frequency of genotype AA (dominant homozygous)
    • 2pq = frequency of genotype Aa (heterozygous)
    • q² = frequency of genotype aa (recessive homozygous)
Assumptions of Hardy-Weinberg Equilibrium

For a population to remain in Hardy-Weinberg equilibrium, the following conditions must be met:

  1. No mutation: The gene of interest does not mutate
  2. No gene flow: No migration of individuals into or out of the population
  3. Random mating: Individuals pair without preference for genotype
  4. No natural selection: All genotypes have equal fitness
  5. Infinite population size: To minimize the effects of genetic drift
Testing for Hardy-Weinberg Equilibrium

The Chi-Square test is commonly used to determine if observed genotype frequencies differ significantly from those expected under Hardy-Weinberg equilibrium.

The formula for the Chi-Square test is:

χ² = Σ (Observed - Expected)²/Expected

If the calculated Chi-Square value exceeds the critical value for the appropriate degrees of freedom (typically 1 for a two-allele system), the population is considered not to be in Hardy-Weinberg equilibrium.

Applications

Hardy-Weinberg equilibrium is used in:

  • Population genetics to estimate allele frequencies
  • Forensic science for DNA profiling and matching
  • Medical genetics to study disease prevalence
  • Conservation biology to assess genetic diversity
  • Evolutionary studies to identify selection pressures

What Is the Hardy-Weinberg Equilibrium Calculator?

The Hardy-Weinberg Equilibrium Calculator is an interactive tool that helps you analyze genetic variation within a population. Using a simple set of inputs, it allows you to determine allele and genotype frequencies, and assess whether a population is in genetic equilibrium. If you're specifically interested in calculating allele frequencies, you might also want to check out our Allele Frequency Calculator.

This calculator is based on the Hardy-Weinberg principle, a foundational concept in genetics that states allele and genotype frequencies will remain constant across generations in the absence of evolutionary forces.

Hardy-Weinberg Equation: \( p^2 + 2pq + q^2 = 1 \)

Where:

  • \( p \) = frequency of the dominant allele (A)
  • \( q \) = frequency of the recessive allele (a)
  • \( p^2 \) = expected frequency of homozygous dominant (AA)
  • \( 2pq \) = expected frequency of heterozygous (Aa)
  • \( q^2 \) = expected frequency of homozygous recessive (aa)

How to Use the Calculator

Using the calculator is simple. Follow these steps to get accurate results:

  • Select Input Type: Choose whether to enter genotype counts or an allele frequency.
  • Enter Your Data:
    • If using genotype counts, input the number of individuals for AA, Aa, and aa.
    • If using allele frequency, enter the frequency of the dominant allele (p) between 0 and 1.
  • Choose Display Options: You can opt to show a chi-square test and data visualizations like charts and a Punnett square.
  • Click “Calculate”: The calculator processes your input and displays allele frequencies, expected genotype frequencies, and an optional chi-square test to assess equilibrium.
  • Click “Reset”: Use this to clear all fields and start over.

Key Features

  • Supports input by genotype counts or allele frequency.
  • Displays calculated allele frequencies (p and q).
  • Shows expected genotype frequencies under equilibrium.
  • Includes optional chi-square test to evaluate genetic equilibrium.
  • Visual charts for easier understanding of results.
  • Punnett square display for allele combinations.

Why Use This Calculator?

This tool is useful for students, educators, and researchers who want to explore or teach population genetics. It simplifies the process of applying the Hardy-Weinberg equation and helps you visualize what the results mean for a population’s genetic structure.

It can be used in:

  • Classroom settings for teaching biology or genetics
  • Research to test genetic variation and stability
  • Conservation planning for maintaining genetic diversity
  • Medical genetics to explore disease-related gene frequencies

Frequently Asked Questions (FAQ)

What does it mean if a population is in Hardy-Weinberg equilibrium?

It means the population’s allele and genotype frequencies are stable from one generation to the next, indicating no evolutionary forces are acting on the gene in question.

What if my chi-square test shows a deviation?

If the p-value is less than 0.05, the population likely deviates from Hardy-Weinberg equilibrium. This could suggest factors like selection, mutation, or non-random mating are influencing the population.

Can I use this calculator without genotype counts?

Yes. You can enter a dominant allele frequency (p), and the calculator will estimate genotype frequencies and build a model based on a sample size of 100.

Do I need to be an expert in genetics to use this?

No. The tool is designed for anyone interested in understanding basic genetic patterns. Just input your data and let the calculator do the rest.

Is the chi-square result always required?

No. You can choose to hide the chi-square section if you're only interested in the allele and genotype frequencies.