Question

The son of a haemophilic man may not get this genetic disorder. Mention the reason.

Answer 1

The son of a haemophilic man may not get the genetic disorder haemophilia because haemophilia is a sex-linked recessive disorder caused by a defective gene located on the X chromosome. Since a male has one X and one Y chromosome (XY), a haemophilic man has the defective gene on his single X chromosome. However, he passes his Y chromosome, not his X chromosome, to his sons. Therefore, sons do not inherit the defective X chromosome from their father and hence will not have haemophilia. Instead, the haemophilic father passes his defective X chromosome to all his daughters, who then become carriers of the disorder but typically do not show symptoms because they have a second normal X chromosome. Thus, the inheritance pattern explains why a haemophilic father cannot pass the disorder directly to his sons, but can pass the carrier status to his daughters.