Hemophilia is a genetic disorder that inherited by X-linked recessive pattern. A daughter needs 2 genes to have the disease(or 1 gene to become carrier) but a son only needs to get 1 defect genes from his mother(X gene in male must come from mother). If Xh defected gene and X normal genes, the punnett square would be:
Father(XY)
X Y
Mother Xh XhX XhY ------>XhX= carrier , XhY= sick
(Xh X) X XX XY ------>healthy
