In a population of 200 individuals, 72 are homozygous dominant (AA), 96 are heterozygous (Aa) and the rest are homozygous recessive (aa). What is the frequency of the recessive allele (a)?
Answer
0.4
The correct answer is 0.4 — Thus the frequency of allele a is 0.4.
Step-by-step solution
- Calculate the number of aa individuals: 200 - 72 - 96 = 32.
- Count the total number of alleles in the population: 2 × 200 = 400.
- Count the number of a alleles: each aa contributes 2 a alleles (2 × 32 = 64) and each Aa contributes 1 a allele (96). Total a alleles = 64 + 96 = 160.
- Allele frequency of a = (total a alleles) / (total alleles) = 160 / 400 = 0.4.
- Thus the frequency of allele a is 0.4.
Common mistake: Forgetting to double count the a alleles in homozygous recessive individuals.
Concept tested: Allele frequency calculation
Published · How this solution was prepared and checked
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