Individuals that are heterozygous for sickle-cell anemia are more resistant to malaria than those that do not have a sickle-cell allele. Why does the sickle-cell allele not become fixed in the population?
A)Individuals homozygous for the sickle-cell allele do not have the same resistance to malaria.
B)Individuals that are homozygous without the sickle-cell allele produce more offspring than those with the sickle-cell allele.
C)Individuals that are homozygous for the sickle-cell allele have sickle-cell anemia, and are at a fitness disadvantage.
D)Individuals heterozygous for the sickle-cell allele die earlier than either of the homozygous individuals.
E)Analysis indicates the allele is becoming fixed in the population.

Question

Quizplus · Accepted Answer

Individuals that are homozygous for the sickle-cell allele have sickle-cell anemia, which is a serious medical condition that reduces their fitness and can even lead to death. This means that they are at a significant disadvantage compared to heterozygotes or individuals without the allele. As a result, natural selection acts against the homozygous sickle-cell allele, preventing it from becoming fixed in the population. While heterozygotes have the advantage of resistance to malaria, it is not enough to outweigh the negative effects of being homozygous for the sickle-cell allele.

Individuals That Are Heterozygous for Sickle-Cell Anemia Are More Resistant