Question

Differentiate between the pattern of inheritance in humans of the blood diseases, haemophilia and thalassemia.

Answer 1

Mendelian disorders are genetic diseases that arise due to mutation or alteration in a single gene, such as haemophilia and thalassemia.

1. Haemophilia: Haemophilia is a genetic disorder in which the blood fails to clot properly because one of the clotting factors is defective. It is an X-linked recessive disorder and is therefore more common in males than in females. Males usually inherit it from a carrier mother and may become sterile. Females are rarely affected because both of their X-chromosomes must carry the defective gene for the disease to appear. This disorder results in excessive or spontaneous bleeding even after minor injuries.
2. Thalassemia: Thalassemia is an inherited autosomal recessive blood disorder. In this condition, abnormal haemoglobin is produced, which reduces the oxygen-carrying capacity of the blood. As a result, red blood cells are destroyed, leading to anaemia. Individuals with one affected parent become carriers of the disease. If both parents are carriers, there is a 25% chance that their child will suffer from thalassemia. It is a serious disorder that may shorten life expectancy, and its symptoms and severity vary depending on the type.