4. In areas of sub-Saharan Africa, equilibrium frequencies of the HbS allele rea

Question

4. In areas of sub-Saharan Africa, equilibrium frequencies of the HbS allele reach as
high as 0.2, this despite the fact that when homozygous, individuals suffer severe
anemia, and most die as young children.
a. Explain why this allele is maintained at such high frequency in this area.
b. Assuming the fitness of the HbS/HbS homozygotes is 0, what is the expected
relative fitness of the Hb+/Hb+ homozygotes at equilibrium?
c. What would you predict to be the equilibrium frequency of the HbS allele in the
United States? (assume a mutation rate of 1 x 10-7, and that heterozygotes have the
same fitness as the Hb+/Hb+ homozygotes).
d. HbS allele frequencies are not at this equilibrium in African American populations
in the United States, why?

5. What is the inbreeding coefficient for the offspring of a) a full sib mating, b) an uncle/niece mating, c)1st cousing mating? Explain why such close inbreeding in a generally outbred population may lead to decreased fitness.

Explanation / Answer

4. In areas of sub-Saharan Africa, equilibrium frequencies of the HbS allele reach as high as 0.2, this despite the fact that when homozygous, individuals suffer severe anemia, and most die as young children. a. Explain why this allele is maintained at such high frequency in this area. this allele is maintained at such high frequency in this area . because of epidemic of malaria and hetrozygotic advantage of sickle trait b. Assuming the fitness of the HbS/HbS homozygotes is 0, what is the expected relative fitness of the Hb+/Hb+ homozygotes at equilibrium? Hb+/Hb+ homozygotes normal one c. What would you predict to be the equilibrium frequency of the HbS allele in the United States? (assume a mutation rate of 1 x 10-7, and that heterozygotes have the same fitness as the Hb+/Hb+ homozygotes). due lack of malaria diseae d. HbS allele frequencies are not at this equilibrium in African American populations in the United States, why? because of operation of evolutionary forces 1.various kinds of mating patterns 2. migration 3. mutation and natural selection 4.genetic drift etc

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