Question

Question 1:

You are a population geneticist interest in the frequency of the sickle-cell allele in a small town in Sudan. From hospital records you know that people in the previous generation had 4% incidence of sickle-cell anemia. Assuming Hardy-Weinberg equilibrium, what is the expected frequency of the sickle-cell allele in the current generation, and what is the predicted frequency of heterozygotes in the population?

Question 2:

Answer 1

1. If 4% of the population have sickle cell anemia, then 4 individuals in 100 are having the sickle cell anemia. Sickle cell anemia is a recessive disorder and hence the q² value = 4/100 = 0.04 and q=0.2. The frequency of recessive allele in this population is 0.2 which is the expected frequency of the sickle cell allele in the current generation and the dominant allele frequency is p = 1-0.2 = 0.8. The predicted frequency of heterozygotes in the generation = 2pq = 2 x 0.8 x 0.2 = 0.32.

2. If the mother has an X-linked recessive disease and father is a normal person, then a cross between them will produce all diseased male and all carrier females. Hence for the child to be normal, without symptoms, the egg from the mother should be fertilised with the sperm of the father that has X chromosome in it instead of the Y chromosome. It produces a heterozygotic female who has no symptoms but is a carrier. Hence the child should be a girl.

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