A woman with hemophilia and a man without get married. What are the chances that their first child will have hemophilia?

Since hemophilia is a sex-linked recessive trait carried on the X chromosome, we can determine the probability of their child having hemophilia (denoted by H) based on the inheritance pattern.

Since the woman has hemophilia (H), she must have two copies of the affected gene (XH XH). The unaffected (healthy) man will have two normal copies of the X chromosome (XH Y).

When they have children:

- All of their sons (XY) will be healthy (XH Y) because they will receive one unaffected X chromosome from their father.

- All of their daughters (XX) will be carriers (XH XH) like their mother, as they will receive one affected X chromosome from her.

Therefore, there is a 0% chance that their first child, regardless of gender, will have hemophilia.