Question

Thalassemia and sickle cell anaemia are caused due to a problem in globin molecule synthesis. Select the correct statement.
A. Sickle cell anemia is due to a quantitative problem of globin molecules.
B. Both are due to qualitative defects in globin chain synthesis.
C. Both are due to a quantitative defect in globin chain synthesis.
D. Thalassemia is due to less synthesis of globin molecules.

Answer 1

For better understanding, let us understand the first meaning of qualitative and quantitative. Qualitative means the product is changed whereas quantitative means change in amount like increased or decreased production.

Complete answer:
Sickle cell anemia is an autosomal disease. The red blood cells formed due to low oxygen availability changes the shape of itself to sickle-shaped due to the presence of a defective gene. When these red blood cells which contain haemoglobin face oxygen tension then their haemoglobin start to aggregate together and start forming stiff fibres. These fibres change their shape to sickle. Due to this these sickle shaped cells can not be passed through the capillaries and get stuck. The genetic reason for causing sickle cell anemia is due to substitution of glutamic acid by valine at the sixth position in the beta globin chain of haemoglobin. This leads to single base substitution and results in the change of biconcave red blood cells into sickle shaped.
Thalassemia is the defect of the alpha or beta globin chain of haemoglobin. In thalassemia the red blood cells synthesis becomes abnormal leading to decreased synthesis of the globin chains. Thalassemia is a quantitative problem as less globin molecules are synthesized.

Hence the correct answer is option D i.e. Thalassemia is due to less synthesis of globin molecules.

Note:- Thalassemia can be of two types based on the defect in which chain i.e. alpha thalassemia and beta thalassemia. These chains are basically affected by the mutations. Thalassemia is an inherited disease i.e parents must be carriers for it to occur.