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:

• A carrier for an X - linked recessive disorder has one normal allele and one recessive allele. Females have two X chromosomes (\(XX\)).
• \(X^{R}X^{r}\): One normal (\(X^{R}\)) and one recessive (\(X^{r}\)) allele - carrier.
• \(X^{r}X^{r}\): Two recessive alleles - affected (not carrier).
• \(X^{R}Y\) and \(X^{r}Y\): Males (\(XY\)) - cannot be carriers (only one X chromosome).

Answer:

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