In central Africa, the frequency (percentage) of the sickle-cell gene, compared to the normal gene, has remained stable over the years because the sickle-cell gene protects against malaria. In the United States, malaria was eradicated shortly before World War II by eliminating the mosquito that spreads the disease. What has likely happened to the frequency of the sickle-cell gene in African Americans living in the United States since the elimination of malaria?
A) The sickle-cell gene has disappeared from the African American population.
B) The normal gene has disappeared from the African American population.
C) The frequency of the sickle-cell gene has increased.
D) The frequency of the sickle-cell gene has decreased.

Question

Quizplus · Accepted Answer

The sickle-cell gene confers a survival advantage in areas where malaria is prevalent, as carriers are less likely to suffer from severe forms of malaria. In the United States, where malaria has been eradicated, this advantage is no longer present, leading to a decrease in the selective pressure for the sickle-cell gene. Consequently, its frequency in the African American population is likely to have decreased over time.

In Central Africa, the Frequency (Percentage) of the Sickle-Cell Gene