Question

(a) Write two closely linked genes that control \(\alpha\)-thalassemia.
(b) Differentiate between thalassemia and sickle cell anaemia on the basis of their effect on globin molecule of Haemoglobin.

Hint:

Thalassemia affects the quantity of globin chains, while sickle cell anaemia affects the quality of the globin molecule due to structural change.

Answer 1

(a) The two closely linked genes that control \(\alpha\)-thalassemia are \(HBA1\) and \(HBA2\), which are present on chromosome 16.
(b)

• Thalassemia: Caused by deletion or mutation of globin genes, leading to reduced or absent synthesis of one of the globin chains. The structure of the globin molecule is normal, but the quantity is insufficient.
• Sickle Cell Anaemia: Caused by a point mutation in the \(\beta\)-globin gene, resulting in abnormal hemoglobin (HbS). The globin molecule becomes deformed under low oxygen conditions, causing sickling of RBCs.