Sickle cell anaemia has not been eliminated from African population as
Sickle cell anaemia has not been eliminated from African population as
The correct option is D It provides immunity against malaria.
Sickle cell anaemia is caused by a missense mutation in the Hbb gene that codes for β chain. Replacement of A by T at the 17th nucleotide of the Hbb gene changes the codon GAG (glutamic acid) to GTG (which encodes valine). The mutated allele Hbs encodes the abnormal haemoglobin molecules which stick to one another and cause stiffness and sickle shape of red blood cells. The sickle-shaped RBC block and damage the vital organs and tissue. The hemoglobin-Beta gene is located on chromosome 11 and the heterozygotes have normal RBCs which means that disease is governed by the recessive gene. Option A is incorrect. The homozygotes for Hbs do not survive which means that homozygous state is fatal; option C is incorrect. The heterozygotes, HbbHbs, show increased resistance to malaria and therefore, have the survival advantage in regions where malaria is a common disease. That’s why sickle cell anaemia has not been eliminated from African population who reside in malaria-prone area. This makes option D correct answer.
Sickle cell anaemia is caused by a missense mutation in the Hbb gene that codes for β chain. Replacement of A by T at the 17th nucleotide of the Hbb gene changes the codon GAG (glutamic acid) to GTG (which encodes valine). The mutated allele Hbs encodes the abnormal haemoglobin molecules which stick to one another and cause stiffness and sickle shape of red blood cells. The sickle-shaped RBC block and damage the vital organs and tissue. The hemoglobin-Beta gene is located on chromosome 11 and the heterozygotes have normal RBCs which means that disease is governed by the recessive gene. Option A is incorrect. The homozygotes for Hbs do not survive which means that homozygous state is fatal; option C is incorrect. The heterozygotes, HbbHbs, show increased resistance to malaria and therefore, have the survival advantage in regions where malaria is a common disease. That’s why sickle cell anaemia has not been eliminated from African population who reside in malaria-prone area. This makes option D correct answer.
