Allele Frequency Calculator

The allele frequency calculator helps you determine the frequency of alleles in a population and calculate carrier probabilities for genetic traits. This tool is based on the Hardy-Weinberg equilibrium equation, a fundamental principle in population genetics.

Understanding Allele Frequency

Allele frequency describes how often a particular variant of a gene (allele) occurs in a population. This information is crucial for:

• Calculating carrier probabilities for genetic diseases
• Understanding genetic diversity in populations
• Predicting inheritance patterns
• Assessing genetic disease risk

The Hardy-Weinberg Equation

The Hardy-Weinberg equation is the foundation of population genetics:

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

Where:

• ( p ) = frequency of the dominant (healthy) allele
• ( q ) = frequency of the recessive (mutant) allele
• ( p^2 ) = frequency of homozygous dominant individuals (AA)
• ( 2pq ) = frequency of heterozygous individuals (Aa) - carriers
• ( q^2 ) = frequency of homozygous recessive individuals (aa) - affected individuals

Common Recessive Diseases and Their Frequencies

Here are some examples of recessive genetic diseases and their frequencies in different populations:

Disease	Prevalence
Albinism	1 in 10,000 (general population)
Cystic fibrosis	1 in 2,500 (Caucasian population)
Sickle cell anemia	1 in 600 (African-American population)
Tay Sachs	1 in 3,600 (Ashkenazi Jewish population)
Phenylketonuria	1 in 15,000 (Caucasian population)

How to Use the Calculator

1. Enter the frequency of the disease in the population as a decimal number
   • For example, if a disease affects 1 in 2,500 people, enter 0.0004 (1/2500)
2. Click “Calculate” to see the results
3. The calculator will show:
   • Healthy allele frequency (p)
   • Mutant allele frequency (q)
   • Carrier frequency (2pq)
   • Carrier ratio (1 in X people)

Important Notes

• Different populations may have different allele frequencies for the same traits
• Carrier frequency is typically much higher than disease frequency
• This calculator assumes the population is in Hardy-Weinberg equilibrium
• Results are theoretical and may vary in real populations

Applications

The allele frequency calculator is useful for:

• Genetic counselors assessing inheritance risk
• Researchers studying population genetics
• Students learning about genetic inheritance
• Healthcare providers discussing genetic disease risk

Limitations

Remember that this calculator:

• Assumes random mating in the population
• Doesn’t account for new mutations
• Assumes no selection pressure
• Works best for large populations
• Provides theoretical probabilities

Note: This calculator is for educational purposes only. For medical advice about genetic conditions, please consult a healthcare professional or genetic counselor.

References

1. Hardy, G.H. (1908). “Mendelian proportions in a mixed population”
2. Weinberg, W. (1908). “Über den Nachweis der Vererbung beim Menschen”
3. National Human Genome Research Institute - Population Genetics