At a biological level, ?A?S heterozygotes suffer fewer cases of malaria than ?A?A homozygotes, and when they do get malaria, their disease is less severe. What is the biological explanation for the heterozygous advantage?
A) The ?A?A homozygotes have a shortened average life span of their red blood cells, and the shorter RBC life spans interrupt the developmental cycle of Plasmodium larvae by causing the parasites to mature and reproduce rapidly.
B) The ?A?S heterozygotes have a shortened average life span of their red blood cells, and the shorter RBC life spans interrupt the developmental cycle of Plasmodium larvae by preventing many of the immature parasites from reaching maturity.
C) The sickle-cell shape of the RBCs in ?A?S heterozygotes causes the Plasmodium larvae to become stuck in the RBC aggregates, which prevents reproduction.
D) The anemia associated with SCD makes the ?A?S heterozygotes less attractive to mosquitoes, so they experience fewer mosquito bites and less opportunity for infection by Plasmodium larvae.
E) The ?A?S heterozygotes are bitten by mosquitoes less frequently, and when they are infected, the sickle-cell shape of the RBCs in ?A?S heterozygotes causes the Plasmodium larvae to become stuck in the RBC aggregates, which prevents reproduction.
B
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