Question

Which of the following statements regarding selection is false?

Select one:

a. The frequency of the cystic fibrosis allele (r) will decrease in a population, but will not reach zero

b. The frequency of the sickle cell allele (s) is more common worldwide than the cystic fibrosis allele

c. In the United States, selection has a negative impact on rr but a positive impact on ss

d. Selection has a neutral impact on both RR and SS

e. all statements are true

answer is c

Answer 1

1. Answer: Option C is correct
Explanation:
Both Cystic fibrosis and Sickle cell anemia are autosomal recessive disorders.
Both of them are deleterious disorders. Hence, they are subjected to negative selection.

However, there is a heterozygote advantage for the sickle cell allele in African regions where the malarial disease is prevalent. i.e. HbA/HbS heterozygotes exhibit resistance to Malaria. Due to this selection pressure, the HbS allele is maintained in these population seven though it is a deleterious allele.

However, such a positive selection pressure does not exist in the US due to less prevalence of Malaria. As a result, both Cystic fibrosis and Sickle cell anemia are equally subjected to negative selection in the US.