Question

which allele combination represents a female who is a carrier for an x - linked recessive disorder?
○ ( x^r x^r )
○ ( x^r x^r )
○ ( x^r y )
○ ( x^r y )

Explanation:

• For X - linked recessive disorders, females have two X chromosomes. A carrier has one normal (dominant, \(X^{R}\)) and one mutant (recessive, \(X^{r}\)) allele, so genotype \(X^{R}X^{r}\).
• \(X^{r}X^{r}\) is an affected female, \(X^{R}Y\) is a normal male, \(X^{r}Y\) is an affected male.

Answer:

A. \(X^{R}X^{r}\)