- The following genotypes were observed in a population
Genotype Number
HH 90
Hh 60
hh 50
Which of the following is the correct frequency of H allele and what will be the expected number of HH in the given population?
(1) 0.60 and 72 (2) 0.80 and 96
(3) 0.50 and 32 (4) 0.30 and 90
How to Calculate Allele Frequency and Expected Genotype Numbers: A Step-by-Step Guide
Population genetics relies on understanding how alleles and genotypes are distributed in a population. The Hardy-Weinberg principle provides a straightforward method for calculating allele frequencies and predicting expected genotype numbers. Let’s apply these concepts to a real example.
Given Data
| Genotype | Number of Individuals |
|---|---|
| HH | 90 |
| Hh | 60 |
| hh | 50 |
Step 1: Calculate the Frequency of the H Allele
To find the frequency of the H allele, use the following formula:
Frequency of H=2×Number of HH+Number of Hh2×Total individuals
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Number of HH = 90
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Number of Hh = 60
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Total individuals = 90 + 60 + 50 = 200
Frequency of H=2×90+602×200=180+60400=240400=0.60
Step 2: Calculate Expected Number of HH Individuals
Using Hardy-Weinberg equilibrium, the expected frequency of HH is p2, where p is the frequency of the H allele.
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p=0.60
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Expected frequency of HH (p2) = 0.602=0.36
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Expected number of HH = 0.36×200=72
Step 3: Match with the Correct Option
From the options provided:
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(1) 0.60 and 72
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(2) 0.80 and 96
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(3) 0.50 and 32
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(4) 0.30 and 90
The correct answer is (1) 0.60 and 72.
Why This Matters
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Genetic Counseling: Helps estimate carrier and disease frequencies.
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Population Genetics: Essential for studying genetic structure and detecting evolutionary changes.
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Research: Provides a baseline for comparing observed and expected genotype frequencies.
Conclusion
For the given population, the frequency of the H allele is 0.60, and the expected number of HH individuals is 72 under Hardy-Weinberg equilibrium.
Correct answer: (1) 0.60 and 72
