Question

A boy suffers from haemophilia. What is true of the inheritance of this case?

विकल्प

• His mother could be normal (homozygous)

• His mother could be a carrier of this disorder

• He has inherited this disease from his father

• His maternal grandfather was normal

Answer 1

His mother could be a carrier of this disorder

Explanation:

Haemophilia is a sex-linked recessive disorder caused by a gene located on the X-chromosome. Since males have only one X-chromosome (XY), inheriting one defective X chromosome from their mother will cause the disease. The mother is usually a carrier of the disorder (heterozygous) and does not show symptoms, as females have two X-chromosomes (XX). The father cannot pass haemophilia to his son because he passes his Y-chromosome to male offspring, not his X. Therefore, the boy inherits the defective gene from his mother, who may be a carrier, while the maternal grandfather’s status is not necessarily normal or affected in this case.