Question

1. a woman who has hemophilia marries a normal man.

how many children will have the disease? ____
what is the sex of the child with the disease? ____

Explanation:

Step1: Define genotype notation

Hemophilia is an X-linked recessive disorder. Let:

• $X^h$ = X chromosome with hemophilia allele
• $X^H$ = Normal X chromosome
• $Y$ = Y chromosome (no allele for this trait)

A woman with hemophilia has genotype $X^hX^h$; a normal man has genotype $X^HY$.

Step2: Set up Punnett square

	$X^h$	$X^h$
$Y$	$X^hY$	$X^hY$

Step3: Analyze offspring genotypes

• $X^HX^h$: Carrier female (no disease)
• $X^hY$: Affected male (has disease)

2 out of 4 (50%) offspring have the disease, all male.

Answer:

How many children will have the disease? 50% (or 1 out of every 2 children)
What is the sex of the child with the disease? Male