Question

African American populations have a relatively high incidence of sickle cell disease. The reason for this is:

1) mutations that occurred after they arrived in the U.S.
2) the US is becoming increasingly a malarial zone
3) forced migration
4) sickle cell disease is advantageous in early life

Answer 1

African Americans have a higher incidence of sickle cell disease due to the historical prevalence of malaria in Africa. The sickle cell trait provides natural resistance to malaria, increasing the chances of survival and passing on the trait.

Step-by-step explanation:

African Americans have a relatively high incidence of sickle cell disease due to the historical prevalence of malaria in Africa. Malaria is caused by a parasite that is transmitted through mosquito bites, and individuals with the sickle cell trait have some natural resistance to malaria. Therefore, in regions where malaria is common, having the sickle cell trait provides a survival advantage and increases the chances of passing on the trait to future generations.

The allele (S) for sickle-cell anemia found in African descended people in the Western Hemisphere is believed to have come from West Africa as a result of the slave trade, not as a new mutation or increased malarial regions in the U.S. As a result, the protective anti-malarial effects of having just one copy of the mutant gene have kept the allele relatively common among people of African descent, despite the potential for severe disease in the case of homozygous individuals.