The Sickle-Cell Anemia Allele, S, Experiences Strong Negative Selection Because

Multiple Choice

The sickle-cell anemia allele, S, experiences strong negative selection because of its deleterious effect on homozygotes, yet the allele is maintained at frequencies higher than expected because having only one copy can increase survival in areas where malaria is prevalent. This is an example of

A) heterozygote advantage.
B) antagonistic pleiotropy.
C) balancing selection.
D) a and c
E) a, b, and c