In sickle cell anaemia glutamic acid is replaced by valine. Which one of the following triplets codes for valine ?

Options

A. G G G
B. A A G
C. G A A
D. G U G

Answer

D

Explanation

The sickle-cell anaemia is caused by the substitution of glutamic acid (Glu) by valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule. The substitution of amino acid in the globin protein results due to the single base substitution at the sixth condon of the beta globin gene from GAG to GUG. The mutant haemoglobin molecule undergoes polymerisation under low oxygen tension causing the change in the shape of the RBC from biconcave disc to elongated sickle like structure.