Homozygotes with Two Sickle-Cell Alleles Are Selected Against Because of Mortality

Multiple Choice

Homozygotes with two sickle-cell alleles are selected against because of mortality. However, heterozygotes for sickle-cell allele experience little effects of sickle allele and are more likely to survive malaria. The net effect of this exposure produced evolutionary change in areas where malaria is endemic by ________.

A) causing sickle-cell allele
B) increasing sickle-cell allele frequency
C) distortion of red blood cells
D) increasing the number of infected mosquitoes