Question

The human male never passes on the gene for haemophilia to his son .justify the statement

Answer 1

It is a X-linked recessive disease that shows crisscross inheritance. The haemophilic father passes the gene of haemophilia to carrier daughter. ... As it is a X linked disorder and father (human male) always gives his Y chromosome to son, so father can never transmit the gene of haemophilia to his son

Answer 2

Haemophilia is a disorder in which blood fails to clot. It  is a X-linked recessive disease that shows crisscross inheritance. The haemophilic father passes the gene of haemophilia to carrier daughter. In turn, the carrier daughter transmits the haemophilic gene to her son.  As it is a X linked disorder and father (human male) always gives his Y chromosome to son, so father can never transmit the gene of haemophilia  to his son