Hemophilia is a sex-linked recessive trait which means that the males having one altered copy of the gene is enough to cause the medical condition( as they have only one X chromosomes and females have two)
In this case the genotype of father and son is such that they are affected by hemophilia.The son has mother's X chromosome and father's Y chromosome.
XhY is the genotype of father and son. As mother would be heterozygous because she is not affected, her genotype will be XHXh.
Just as tubes within the stems and leaves of plants transport water, arteries and veins within animals transport blood with the required nutrients for our bodies.
