Question

Sickle-cell anaemia is

• A. caused by substitution of valine by glutamic acid in the beta globin chain of haemoglobin
• B. caused by a change in a single base pair of DNA
• C. characterised by elongated sickle like-RBCs with a nucleus
• D. an autosomal linked dominant trait

Answer 1

Answer: (B)

Sickle-cell anaemia is an autosomal recessive disorder, where RBCs because sickle-shaped. It is due to the abnormal haemoglobin and homozygous genotype $H{b}^S\text{-}H{b}^S.$ This disease is caused by a single gene which in heterozygous condition causes moderate sickling (sickle-cell trait) and In homozygous condition causes severe effect (sickle-cell anaemia).