The text notes that an alternate allele of the hemoglobin gene can cause sickle-cell anemia when a person is homozygous for this allele, but that a person who is heterozygous for the allele actually can derive a benefit from it–protection from malaria. In the United States, 8 percent of African Americans are carriers for the sickle-cell allele, while in central Africa the figure is 20 percent. What could account for this difference? Assess. Answer:
The difference could be accounted for by the prevalence of malaria disease in central Africa. Heterozygous carriers of the disease are resistant to malaria. Furthermore, there is a at leasr a 25% chance that the heterozygous trait is passed on to the next generation. Malaria is more prevalent in central Africa than in America. African Americans are not as exposed to malaria as central Africans are. Therefore, the sickle-cell trait is being faced out gradually in African Americans.
Central Africans on the other hand are continually exposed to the disease. The trait therefore persists in their genome. More malaria resistant individuals are born. Unfortunately, they are heterozygous carriers of the sickle-cell trait. When two heterozygous individuals produce offsprings, there is a 25% chance that a one of them is a homozygous for sickle-cell disease. Therefore, the trait persists in central Africans.Order now