Question

Explain why the sickle-cell gene does not benefit anyone in the United States, but if may be very advantageous to someone living in rural Zambia, Africa.

Answer 1

• Sickle cell anemia is a genetic disease that slightly alters the structure of hemoglobin, the oxygen carrying protein in red blood cells. This modified hemoglobin, when not carrying oxygen, tends to clump with other deoxygenated hemoglobin, deforming red blood cells and causing blood to clot throughout the body. T
• he disease is prevalent in Africa where incidence of malaria is high because sickle cell anemia imparts some resistance to malaria. Because the United States does not have a problem with malaria, the incidence of sickle cell anemia has decreased in the African-American population.
• Since sickle cell anemia is only advantageous in regions where incidence of malaria is high, it occurs less often in populations rarely exposed to malaria. For millions of years, whenever malaria swept through an area of Africa, those with sickle cell trait had a greater chance of survival than those without the trait. Those with sickle cell trait perpetuated the disease.
• For instance, in the United States, where malaria is not a problem, only 8% of the African-American population has sickle cell trait, and 0.25% have full blown sickle cell anemia.Sickle cell anemia and even sickle cell trait are enough of a disadvantage in malaria-free parts of the world4that their frequency of incidence decreases.