Question

Sickle cell anaemia is caused due to

• A. change of amino acid in alpha chain of haemoglobin
• B. change of amino acid in beta chain of haemoglobin
• C. change of amino acid in both alpha and beta chains of haemoglobin
• D. change of amino acid either alpha or beta chains of haemoglobin

Answer 1

The correct option is B change of amino acid in beta chain of haemoglobin

Sickle cell anaemia is caused due to defective haemoglobin production. Haemoglobin is made up of 4 polypeptide chains- 2 alpha chains and 2 beta chains. Each beta chain is made up of 141 amino acids. Glutamic acid at the $6^{\mathrm{th}}$ position of the beta globin chain is replaced by valine, which causes the change in the structure of haemoglobin.
Sickle cell anaemia is not caused by mutations in the alpha chain of haemoglobin. Change in either a (alpha) or b (beta) chains might lead to other disorders, but sickle cell anaemia is specifically caused due to change in amino acid sequence in the beta chain only. Hence, option a, c, and d are incorrect.