Question

which allele combination represents a female who is heterozygous for a sex-linked trait?

• \\(x^r y\\)
• \\(x^r y\\)
• \\(x^r x^r\\)
• \\(x^r x^r\\)

Explanation:

Identify female sex chromosomes

Females have two X chromosomes (\(XX\)), while males have one X and one Y chromosome (\(XY\)). Therefore, the combination must contain two X chromosomes.

Identify heterozygous state

A heterozygous individual has two different alleles for a given gene. For a sex-linked trait on the X chromosome, this means having one dominant allele and one recessive allele, represented as \(X^R X^r\).

Evaluate the options

• \(X^R Y\): Male with a dominant allele.
• \(X^r Y\): Male with a recessive allele.
• \(X^R X^r\): Female with two different alleles (heterozygous).
• \(X^R X^R\): Female with two identical dominant alleles (homozygous dominant).

Answer:

• (A) \(X^R Y\)
• (B) \(X^r Y\)
• (C) \(X^R X^r\) (Correct answer)
• (D) \(X^R X^R\)