Allele Frequency Calculator

Category: Biology
- March 11, 2025
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Enter Population Counts

For a single gene with two alleles (A and a)

Allele Frequency Results

Population Statistics
Sample Size (N):
100
Number of Alleles:
200
Frequency of A (p)
0.45
Frequency of a (q)
0.55
Genotype Frequencies
AA (p²):
0.2025
Aa (2pq):
0.4950
aa (q²):
0.3025
Genotype Distribution
AA
20.3%
Aa
49.5%
aa
30.3%

Hardy-Weinberg Equilibrium Check

The observed genotype frequencies match the expected Hardy-Weinberg frequencies within a margin of error of 0.01.

Chi-square test: χ² = 0.042, p > 0.05. The population appears to be in Hardy-Weinberg equilibrium.

About Allele Frequencies

  • For a diploid gene locus with two alleles (A and a), the Hardy-Weinberg principle states that p² + 2pq + q² = 1
  • p represents the frequency of the dominant allele A, and q represents the frequency of recessive allele a
  • p + q = 1, meaning the allele frequencies must sum to 1
  • p² represents the frequency of homozygous dominant (AA)
  • 2pq represents the frequency of heterozygous (Aa)
  • q² represents the frequency of homozygous recessive (aa)
  • A population in Hardy-Weinberg equilibrium is not evolving and shows no genetic drift, selection, mutation, or migration

Allele Frequency Calculator

The Allele Frequency Calculator is a tool used in genetics to determine allele and genotype frequencies in a population. It applies Hardy-Weinberg principles to analyze inheritance patterns, selection effects, and genetic variation over generations.

Key Hardy-Weinberg Equilibrium Equations:

For a single gene with two alleles, A and a:

\[ p + q = 1 \]

\[ p^2 + 2pq + q^2 = 1 \]

Where:

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

In selection studies, the allele frequency over generations is affected by fitness values:

\[ p' = \frac{p(w_{AA}p + w_{Aa}q)}{\bar{w}} \]

Where \( w_{AA}, w_{Aa}, w_{aa} \) represent the fitness of each genotype, and \( \bar{w} \) is the mean population fitness.

How to Use the Calculator

This calculator offers three ways to determine allele frequencies:

  • Genotype Counts: Enter the number of individuals with AA, Aa, and aa genotypes to calculate allele frequencies.
  • Known Frequencies: If you already know one value (e.g., \( p, q, p^2, q^2, 2pq \)), use this mode to find missing frequencies.
  • Population Genetics: Enter selection coefficients and track allele evolution over multiple generations.

Once you've entered the necessary values, click "Calculate" to see results, including Hardy-Weinberg equilibrium verification and allele frequency trends.

Why This Calculator is Useful

This tool is valuable for:

  • Understanding Genetic Variation: Quickly assess allele distribution in populations.
  • Checking Hardy-Weinberg Equilibrium: Determine if a population is evolving or stable.
  • Studying Evolutionary Changes: Simulate selection effects over generations.
  • Population Genetics Research: Helps researchers, students, and educators analyze genetic inheritance models.

Frequently Asked Questions

What is an allele frequency?

An allele frequency represents the proportion of a specific allele in a population. It is calculated as:

\[ p = \frac{2(\text{AA}) + \text{Aa}}{2N} \]

where \( N \) is the total population size.

What does Hardy-Weinberg equilibrium mean?

A population is in Hardy-Weinberg equilibrium if allele and genotype frequencies remain constant from generation to generation, assuming no mutation, selection, migration, genetic drift, or non-random mating.

How can I determine if a population is in Hardy-Weinberg equilibrium?

Compare observed and expected genotype frequencies using a chi-square test:

\[ \chi^2 = \sum \frac{(O - E)^2}{E} \]

If the result is statistically insignificant (\( p > 0.05 \)), the population is likely in equilibrium.

What happens if a population is not in Hardy-Weinberg equilibrium?

Deviations indicate factors like natural selection, genetic drift, or non-random mating. This suggests the population is evolving.

What is the effect of natural selection on allele frequencies?

Selection alters allele frequencies based on genotype fitness. Favorable alleles increase in frequency over generations, while deleterious ones decrease.

Can allele frequencies change without selection?

Yes. Factors like genetic drift (random fluctuations), mutation, migration, and non-random mating can alter allele frequencies without selection.

Final Thoughts

The Allele Frequency Calculator is a powerful tool for understanding genetic variation and evolutionary processes. Whether analyzing population stability or tracking selection effects, this tool provides key insights into how genes spread over time.