[Campbell Biology P.552] In a region where malaria has been completely eradicated, how would... | Practice Question

In a region where malaria has been completely eradicated, how would individuals who are heterozygous for the sickle-cell allele be selected?

  • A: They would be selected for, as they still retain some advantage over homozygous dominant individuals.
  • B: They would be selected against, due to the mild sickling effects they experience without the compensatory advantage of malaria resistance.
  • C: They would experience no selection pressure, as their sickle-cell trait is completely benign.
  • D: They would become the dominant genotype, as their trait allows for better oxygen transport.

Explanation

In a malaria-free region, the selective advantage of heterozygotes malaria resistance is removed. However, they still experience 'some sickling' which, while not causing full disease, represents a slight disadvantage in terms of red blood cell function compared to homozygous dominant individuals. Therefore, without the balancing selection from malaria, heterozygotes would be selected against.