Sickle Cell Anemia is caused by having two copies of the recessive h allele. The

Question

Sickle Cell Anemia is caused by having two copies of the recessive h allele. The dominant allele H produces normal-shaped red blood cells. You are an Evolutionary Geneticist studying Sickle cell Anemia in a remote village in the Congo region of Africa. You sample all of the people living in the village and there are 200 people.

You determine that 80 people have full Sickle Cell Anemia. Using what you know of the Hardy-Weinberg Equilibrium Theory, and assuming this population is in Hardy-Weinberg Equilibrium, answer the following questions.

1. What is the observed frequency of the (hh) genotype in this population? (show all work)

2. What is the predicted frequency of the sickle cell allele (h) in this population? (show all work)

3. What is the predicted frequency of the homozygous genotype (HH) in this population? (show all work)

4. What is the predicted frequency of the heterozygous genotype in this population? (show all work)

Explanation / Answer

According to Hardy-Weinberg equilibrium the equation would be p² + 2pq + q² = 1, where p and q are two different alleles governing the phenotype. In this case we may rewrite it as H2 + 2Hh + h2. Since there are 80 phenotypes which are homozygous recessive, h2 = 80/200 = 0.4. Thus h = Sqrt of 0.4 = 0.6. Since the frequency of both the alleles should add up to 1. H + h = 1, H = 1 - 0.6 = 0.4. Therefore,

1. Frequency of hh = 0.4

2. 0.6 (Sqrt of 0.4)

3. HH = 0.2

4. heterozygous genotype will be 2Hh = 0.5

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