At a Biological Level,βᴬβˢ Heterozygotes Suffer Fewer Cases of Malaria

question 20

Multiple Choice

At a biological level,βᴬβˢ heterozygotes suffer fewer cases of malaria than βᴬβᴬ homozygotes,and when they do get malaria,their disease is less severe.What is the biological explanation for the heterozygous advantage?

• A)The βᴬβᴬ 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 βᴬβˢ 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 βᴬβˢ heterozygotes causes the Plasmodium larvae to become stuck in the RBC aggregates and prevents reproduction.
• D)The anemia associated with SCD makes the βᴬβˢ heterozygotes less attractive to mosquitoes,so they experience fewer mosquito bites and less opportunity for infection by Plasmodium larvae.
• E)The βᴬβˢ heterozygotes are bitten by mosquitoes less frequently,and when they are infected,the sickle-cell shape of the RBCs in βᴬβˢ heterozygotes causes the Plasmodium larvae to become stuck in the RBC aggregates and prevents reproduction.

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