This was a problem from my school. I think I'm pretty sure that I'm right but I just want to be sure.

 

Say there's this guy named Bob with hemophilia. He marries with a woman named Cathy and they have six children, three of them are daughters and three of them are sons. None of them has hemophilia. The daughters, in order from their age, are Jessica, Ellie, and Lauren. Jessica marries with a guy and have two sons with hemophilia and two daughters with no hemophilia. Ellie also marries with a guy and have one son who is also hemophilia. Lauren marries with a guy and among their four children, she has one son with hemophilia and three daughters who are healthy. Bob and Cathy's sons also marry and have children and but none of their children has hemophilia.

 

Questions: Is the trait sex-linked or autosomal? And is it dominant or recessive?

 

In my opinion, because that Bob has hemophilia but none of his children has any and only his grandsons from their daughter has hemophilia, this trait is sex-linked. Of course, hemophilia is a sex-linked trait anyway. But is it dominant or recessive? Well, it is recessive because say, it's dominant then the daughters who would receive the dominant traits from their father and recessive one from their mother would be also affected. But this is not the case here so it has to be recessive.

Haemophilia a hereditary x-linked recessive illness.

my sister has haemophilia, had two blood transfusions and is finally recuperating alright.

 

oh, and what tesseract said, but shouldn't that be obvious?