Question

look at this cross: $x^b x^b$ x $x^b y$ what proportion/percent of the male children are colorblind?

Explanation:

Step1: Analyze Parental Genotypes

The mother's genotype is \( X^B X^B \) (homozygous dominant for normal vision), and the father's genotype is \( X^b Y \) (hemizygous for colorblindness, as colorblindness is X - linked recessive).

Step2: Determine Gametes

• Mother (\( X^B X^B \)) can only produce \( X^B \) gametes.
• Father (\( X^b Y \)) can produce \( X^b \) and \( Y \) gametes.

Step3: Predict Offspring Genotypes

For male children, they inherit the Y chromosome from the father and an X chromosome from the mother. Since the mother only gives \( X^B \), male children will have the genotype \( X^B Y \).

Step4: Determine Colorblindness in Males

Colorblindness (for X - linked recessive) in males requires the \( X^b \) allele. Since male children have \( X^B Y \), they do not have the \( X^b \) allele, so 0% of male children are colorblind.

Answer:

0% (corresponding to the option with "0%")