Assertion : Only a boy child could be born with a substitution of...

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 an abnormal haemoglobin called haemoglobin-S. As found out by Ingram (1958), haemoglobin-S differs from normal haemoglobin-A in only one amino acid $-6^{\text{th }}$ amino acid of $\beta$-chain, glutamic acid, is replaced by valine due to substitution (transversion)$of \mathrm{T}$ by A in the second position of the triplet codon (CTC) which is changed to CAC in the $\beta$-haemoglobin gene situated on chromosome 11.