Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

3. Mutant gene

Explanation:

Haemophilia is a bleeding disorder that slows the blood clotting process. People with this condition experience prolonged bleeding or oozing following an injury, surgery or having a tooth pulled. The major types of this condition are haemophilia A (also known as classic haemophilia or factor VIII deficiency) and haemophilia B (also known as Christmas disease or factor IX deficiency).

Changes in the F₈ gene are responsible for haemophilia A, while mutations in the F₉ gene cause haemophilia B. Mutations in the F₈ or F₉ gene lead to the production of an abnormal version of coagulation factor VIII or coagulation factor IX or reduce the amount of one of these proteins. The altered or missing protein cannot participate effectively in the blood clotting process. As a result, blood clots cannot form properly in response to injury.