Sickle-cell anemia is a disease that alters the structure of hemoglobin, and in turn, can cause severe health problems in individuals if left untreated

Question

The disease is expressed in homozygous recessive individuals, whereas the heterozygous condition usually does not result in any symptoms of the disease. Sickle-cell anemia primarily affects Africans and Caucasians of Mediterranean descent. Typically, when a disease occurs only in the homozygous recessive condition, the incidence of the gene in the population is predicted to decline overtime, particularly when it can be detected either phenotypically or by genetic testing. In East Africa, the disease still occurs in about 40% of the population. Give an explanation for why the incidence of the disease has remained so high in African populations.

Answer 1

The explanation appears to be linked to a more devastating disease in Africa: malaria. Malaria is a disease that kills millions of individuals worldwide. The disease is spread by the bite of mosquitoes, which transmit microorganisms in their saliva into individuals whose blood they drink. The transferred microorganisms seek out red blood cells to infect. Apparently, the malarial parasites can use only healthy, normal-shaped red blood cells. Individuals with sickle-shaped red blood cells are protected from malaria. Thus, the sickle-cell gene has remained in African populations because it confers resistance to the more devastating malarial parasites.