Question :Sickle-cell anaemia as well as thalassemia are autosomal recessive diseases.Why are these diseases more common than expected in certain areas?

Question :Sickle-cell anaemia as well as thalassemia are autosomal rec

1.	Question :Sickle-cell anaemia as well as thalassemia are autosomal recessive diseases.Why are these diseases more common than expected in certain areas?
Answer» Solution : PERSONS heterozygous for sickle-cell trait and THALASSEMIA are more numerous in some African groups living in areas infested with malaria, because MALARIAL parasite is unable to survive in sickle-shaped RBCs or has chances of survival in thalassemic persons. So these HETEROZYGOTES are resistant to malaria and are favoured by natural SELECTION.