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
nice work!

Explanation:

Step1: Analyze the sex - linked inheritance

Since red - green color blindness is a sex - linked recessive trait. A color - blind son has the genotype \(X^{n}Y\). The son gets the \(Y\) chromosome from the father and the \(X^{n}\) chromosome from the mother.

Step2: Determine the mother's genotype

The mother has normal color vision. Since she donates an \(X^{n}\) to the son, her genotype must be \(X^{N}X^{n}\) (heterozygous carrier).

Step3: Determine the father's genotype

The father has normal color vision. Men have one \(X\) and one \(Y\) chromosome. Since he has normal color vision, his genotype is \(X^{N}Y\)

Answer:

The genotypes of the parents are \(X^{N}X^{n}\) (mother) and \(X^{N}Y\) (father)