Hemophilia is an X-linked recessive trait. A male with hemophilia has a daughter with hemophilia. What is/are the possible genotypes of the daughters’ mother?

Answer 1

Hi Janis, I recommend drawing a Punnett square for this question. Remember that males are represented as XY and females are represented as XX. For this question, let's represent the X-linked hemophilia trait with Xh (X, little h) and the normal trait with XH (X, big H). The male with hemophilia would then be XhY--he is a male (XY) and has hemophilia (Xh).

The fact that hemophilia is an X-linked recessive trait means that males with Xh will get hemophilia because they only have one X chromosome. Females, on the other hand, have two X chromosomes, so they need TWO Xh to get hemophilia, or XhXh.

Let's draw a Punnett square to represent the question. The father XhY is crossed with a mom to have a daughter with hemophilia, so the daughter's genotype is XhXh. For this to happen, the mom would have to be either XHXh (a carrier) or XhXh (affected by hemophilia).

Hope this helped!