Question

if a woman is a carrier for a sex linked recessive trait of hemophilia and her husband has hemophilia, which of the following is true? make a punnett square!
50% of daughters and 50% of sons have hemophilia
100% of sons have hemophilia and 100% of daughters are carriers
all daughters will have hemophilia
all sons will have hemophilia

Explanation:

Step1: Define genotypes

Let $X^H$ = normal X chromosome, $X^h$ = X chromosome with hemophilia allele.
Carrier woman: $X^H X^h$, Affected man: $X^h Y$

Step2: Set up Punnett square

$$\begin{array}{c|cc} & X^H & X^h \\ \hline X^h & X^H X^h & X^h X^h \\ Y & X^H Y & X^h Y \\ \end{array}$$

Step3: Calculate offspring probabilities

• Daughters: $X^H X^h$ (carrier, 50%) and $X^h X^h$ (hemophilia, 50%)
• Sons: $X^H Y$ (normal, 50%) and $X^h Y$ (hemophilia, 50%)

Answer:

50% of daughters and 50% of sons have hemophilia