Question

if brian has a son who is color - blind, what is known about the genotype of the sons mother? she must have at least one allele for color blindness. she must have two alleles for color blindness. she cannot be homozygous recessive for the gene for color blindness. she cannot be a heterozygous carrier of the gene for color blindness.

Explanation:

Step1: Understand color - blindness inheritance

Color - blindness is an X - linked recessive disorder. Males have one X and one Y chromosome (\(XY\)). A son gets his Y chromosome from his father (Brian) and his X chromosome from his mother.

Step2: Analyze the son's genotype

Since the son is color - blind (\(X^{b}Y\), where \(X^{b}\) is the recessive allele for color - blindness), the \(X^{b}\) must come from his mother.

Answer:

She must have at least one allele for color blindness.