Question

Assertion: Only a boy child could be born with a substitution of glutamic acid by valine on 6^th codon of β-chain of haemoglobin.

Reason: The gene for the above mutation is found on Y-chromosome.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

Correct option (d)

Explanation:

Sickle cell anaemia is an autosomal recessive hereditary disorder in which the erythrocytes become sickle-shaped under oxygen deficiency as during strenuous exercise and at high altitudes. The disorder or disease is caused by the formation of abnormal hemoglobin called haemoglobin-S. As found out by Ingram (1958), haemoglobin-S differs from normal haemoglobin- A in only one amino acid-6^th amino acid of β-chain, glutamic acid, is replaced by valine due to substitution (transversion) of T by A in the second position of the triplet codon (CTC) which is changed to CAC in the B-haemoglobin gene situated on chromosome 11.