question_answer 63)

    It is said, that the harmful alleles get eliminated from population over a period of time, yet sickle-cell anaemia is persisting in human population. Why?                 

Answer:

                  Sickle-cell anaemia is an autosomal recessive disease caused by haemoglobins anoxygen carrying protein in blood cells. Despite the disease's lethal symptoms, it protects the carrier from malaria. Its allele are most common in the people of African descent (about 7% people of African descent carry anallele) and some other areas where malaria in prevalent. It provides the vital protection from malaria. Individuals with HbAS heterozygotes tend to survive better than individuals with HbSS (homozygotes) as they are not exposed to the same severity of risk.