Question

Assertion :$H{b}^{c}H{b}^{S^C}$,is homozygous condition of sickle cell anaemia. Reason: It occurs due to substitution of glutamic acid by valine at 6th position of $\beta$-chain of haemoglobin.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Sickle cell disease is a genetic disease which is caused due to molecular mutation of gene Hb on chromosome 11 which produces the beta chain of adult hemoglobin.The mutated gene Hbs produces sickle cell haemoglobin.

The 6th amino acid in the beta chain of normal haemoglobin is glutamic acid, in sickle cell haemoglobin this amino acid is replaced by valine. The children that are homozygous produce rigid chains. When oxygen level of the blood drops below a certain level, RBC undergoes sickling. Such cells do not transport oxygen efficiently, they are removed by spleen causing severe anaemia.Sickle cell is an autosomal linked disease in which both male and female progenies can be equally affected.

So, the correct option is 'Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion'