Question

If a son is haemophilic, from where has he got the defective gene, father or mother?

Answer 1

From mother
1. Haemophilia is a sex-linked recessive trait that shows a criss-cross inheritance pattern of transmission. Thus the transmission of the gene occurs from mother to son.
2. It occurred due to the absence of an essential factor necessary for blood clotting, thus even a minor injury can lead to profuse bleeding.