Question

Short / Long answer type questions.
Why does the son of a carrier mother and a normal father suffer from hemophilia whereas the son of a hemophiliac father and normal mother would not?

Answer 1

Cross A	X${}^h$	X
X	XX${}^h$ (carrier daughter)	XX (normal daughter)
Y	X${}^h$Y (hemophilic son)	XY (normal son)

Cross B	X	X
X${}^h$	XX${}^h$ (carrier daughter)	XX${}^h$ (carrier daughter)
Y	XY (normal son)	XY (normal son)

The given situation is true because hemophilic is X-linked inheritance. Son receives the X chromosome from his mother. Therefore carrier mother, who herself is not suffering from the disease because of its recessive condition, will pass on the traits to her son. Whereas normal mother will not pass any traits.