Despite causing a life-threatening disease, the sickle-cell allele in some areas of Africa has remained in high frequency in those populations because it protects against malaria. In the United States, malaria was eradicated shortly before World War II by eliminating the mosquito that spreads the disease. What is likely to happen to the frequency of the sickle-cell allele in African Americans living in the United States?
A) The frequency of the sickle-cell allele will decrease.
B) The frequency of the sickle-cell allele will not change.
C) The sickle-cell allele will disappear from the African American population.
D) The frequency of the sickle-cell allele will increase.
E) The normal allele will disappear from the African American population.

Question

Quizplus · Accepted Answer

The frequency of the sickle-cell allele is likely to decrease in the absence of selective pressure from malaria, which was the primary reason for its high frequency in Africa. In environments where malaria is not a threat, the disadvantageous effects of the sickle-cell allele (when inherited from both parents) are not offset by the protection against malaria, leading to a potential decrease in its frequency over time.

Despite Causing a Life-Threatening Disease, the Sickle-Cell Allele in Some