Question

color blindness is an sex - linked recessive trait. (remember that means its on the x chromosome! females are xx and males are xy.) what is the possibility of having a colorblind child from a mother who is a carrier and a father who is normal?
all boys and 50% of the girls will be color blind
all girls and 50% of the boys will be color blind
all of the girls will be carriers, and 50% of the boys will be color blind
50% of the girls will be carriers, and 50% of the boys will be color blind
50% of the girls will be color blind and 50% of the boys will be color blind

Explanation:

Step1: Determine the genotypes

The mother is a carrier, so her genotype is $X^BX^b$. The father is normal, so his genotype is $X^BY$.

Step2: Set up the Punnett - square

The possible gametes from the mother are $X^B$ and $X^b$, and from the father are $X^B$ and $Y$. The Punnett - square has two rows (mother's gametes) and two columns (father's gametes).

Step3: Analyze the offspring genotypes

When we fill in the Punnett - square:

	$X^B$	$Y$
$X^b$	$X^BX^b$	$X^bY$

For daughters ($XX$), the genotypes are $X^BX^B$ (normal) and $X^BX^b$ (carrier), so 50% of daughters are carriers.
For sons ($XY$), the genotypes are $X^BY$ (normal) and $X^bY$ (color - blind), so 50% of sons are color - blind.

Answer:

D. 50% of the girls will be carriers, and 50% of the boys will be color blind