Assertion (A) : Haemophilia is a recessive sex linked disease.
Reason (R ) : Haemophilia occurs due to mutation of a structural gene on chromosome 15.

Options

A. If both assertion and reason are true reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Answer

C

Explanation

Assertion is true but reason is false.
Haemophilia (also known as bleeder disease) is an popular example of sex linkde inheritance in human beings. Haemophilia is either of two hereditary disorders in which the blood clots very slowely, due to a deficiency of either of two coagulation factors - haemophilia A, due to deficiency of factor VII (antihaemophilic factor) , or haemophilia B, due to deficiency of factor IX (Christmas factor). The patient may experience prolonged bleeding following any injury or wound, and in severe cases there is spontaneous bleeding into muscles and joints. Haemophilia is controlled by a sex-linked gene, which means that it is almost exclusively restricted to males,women can carry the disease - and pass it on to their sons - without being affcted themselves. The genes encoding factors factors VIII and IX have been used in gene therapy trials for haemophilia.
Mutation of a structural gene on chromosome 15 is the molecular basis of Marfan syndrome. This disease is due to domiant mutation resulting in the production of abnormal from of connective tissues and characteristic extreme looseness of joints.