Question

Sickle cell anemia is caused by a recessive mutant, s, at the hemoglobin (S) locus. You analyze the genotypes at the S-locus of 10,000 individuals of unknown geographic origin and find the following genotypic frequencies:

SS: 0.36

Ss: 0.48

ss: 0.16

Which of the following statements best explains these OBSERVED genotypic frequencies?

Group of answer choices

a.) There is inbreeding in this population.

b.) Ss genotypes have the highest fitness.

c.) The population is in Hardy-Weinberg equilibrium.

d.) SS genotypes have intermediate fitness.

e.) ss genotypes have the lowest fitness.

Answer 1

The best statement which explains these OBSERVED genotypic frequencies :-

(c) The population is in Hardy Weinberg Equilibrium.

There are three genotypes in the population :-

• Homozygous dominant (SS)
• Heterozygous (Ss)
• Homozygous recessive (ss)

Frequency of SS, p^2 = 0.36

p = √0.36 = 0.6

Frequency of ss, q^2 = 0.16

q = √0.16 = 0.4

Frequency of Ss = 0.48 and

2pq = 2 × 0.6 × 0.4 = 0.48

Here, p^2 + 2pq + q^2 = 0.36 + 0.48 + 0.16

= 1

Also p+q = 1.

Thus the population is in Hardy Weinberg Equilibrium.

? Inbreeding cannot be calculated from the above as expected and observed heterozygosity is required to calculate the Inbreeding coefficient.

?Options b, d , e are incorrect as there is nothing mentioned about the fittness of the genotype in the population.

Thus the correct answer is (d) The population is in Hardy Weinberg Equilibrium.