A 34-year-old, G, P0, presents for genetic counselling at 12 week's gestation. The patient has two sisters and a brother; her father has hemophilia. Her siblings are not affected, but she has a nephew that is:

Hemophilia is an X-linked recessive disease. These diseases are more common in men than in women. An affected male will not pass the diseases to his sons, but all daughters will be carriers. X-linked recessive diseases are transmitted from carrier women to affected men.