Evolution and gene frequencies — A/L Biology

How do I practise Evolution and gene frequencies?

1 question with a worked solution

1. In a population in Hardy-Weinberg equilibrium, the frequency of individuals affected by an autosomal recessive condition is 0.04. What is the frequency of heterozygous carriers in this population?
   1. A) 0.08
   2. B) 0.64
   3. C) 0.32
   4. D) 0.16
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   Correct answer: C) 0.32

   q² = 0.04 → q = 0.2. Since p + q = 1, p = 1 - 0.2 = 0.8. Frequency of heterozygous carriers (2pq) = 2 × 0.8 × 0.2 = 0.32 (32%).

   Show worked solution

   Step 1: Recessive phenotype frequency q² = 0.04. Step 2: Recessive allele frequency q = √0.04 = 0.2. Step 3: Dominant allele frequency p = 1 - q = 1 - 0.2 = 0.8. Step 4: Heterozygote carrier frequency = 2pq = 2(0.8)(0.2) = 0.32. Answer: 0.32.
   Modelled on: the A/L Biology examination pattern

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Where does Evolution and gene frequencies fit in the syllabus?

Year 1 · Term 2