Question

red - green color blindness is a sex - linked recessive trait in humans. the normal, dominant allele is symbolized with x^{n}, and the recessive allele is symbolized with x^{n}. two people with normal color vision have a color - blind son. what are the genotypes of these parents?
○ x^{n}x^{n} and x^{n}y
○ x^{n}x^{n} and x^{n}y
○ x^{n}x^{n} and x^{n}y
○ x^{n}x^{n} and x^{n}y
○ x^{n}x^{n} and x^{n}y

Explanation:

Step1: Analyze the son's genotype

Since the son is color - blind, his genotype must be \(X^{n}Y\) (because males have one \(X\) and one \(Y\) chromosome, and the recessive allele \(X^{n}\) causes color - blindness).

Step2: Determine the mother's genotype

The mother has normal color vision but must have passed on the \(X^{n}\) allele to the son. So the mother's genotype is \(X^{N}X^{n}\) (a carrier, as she has one normal \(X^{N}\) and one recessive \(X^{n}\) allele).

Step3: Determine the father's genotype

The father has normal color vision. Since males have one \(X\) and one \(Y\) chromosome, and the normal allele is \(X^{N}\), the father's genotype is \(X^{N}Y\).

Answer:

\(X^{N}X^{n}\) and \(X^{N}Y\)