The human male never passes on the gene for haemophilia to his son. Why?

Explanation

The gene responsible for haemophilia is located on X-chromosome and males have only a single copy of X-chromosome with no alternative normal allele. Thus, the father passes only Y-chromosome to his sone and not the haemophilic X-chromosome.
Therefore, in this way, the human male can never pass on the gene for haemophilia to his son.