Hardy–Weinberg: calculating carrier frequency
An autosomal recessive disorder affects 1 in 10,000 people in a population at Hardy–Weinberg equilibrium. Approximately what percentage of the population are heterozygous carriers?
Answer C: explanation for every choice
A
This is q², the frequency of affected individuals, not carriers.
B
This is q, the frequency of the recessive allele. It is not a genotype frequency.
C
Correct. q² = 1/10,000, so q = 0.01 and p ≈ 0.99. Carrier frequency 2pq ≈ 2(0.99)(0.01) ≈ 0.0198, or about 2%.
D
This is roughly p², the homozygous dominant frequency.
TakeawayFor rare recessive traits, carrier frequency ≈ 2q. Start from q² = disease prevalence.
Equation usedHardy–Weinberg
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