[Campbell Biology P.335] What is the evolutionary explanation for the high frequency of the ... | Practice Question

What is the evolutionary explanation for the high frequency of the sickle-cell allele in populations of African descent?

  • A: The allele provides resistance to cystic fibrosis.
  • B: It is a neutral mutation that has drifted to high frequency by chance.
  • C: Heterozygotes have a reproductive advantage because they are more attractive mates.
  • D: Having one copy of the allele provides resistance to malaria.

Explanation

This is a classic example of heterozygote advantage. The text explains that 'having a single copy of the sickle-cell allele reduces the frequency and severity of malaria attacks.' In areas where malaria is common, this survival advantage for heterozygotes outweighs the disadvantage for homozygotes, maintaining the allele's high frequency in the population.