Question

There is a misconception that girls cannot inherit recessive X-linked disorders. Girls can in fact inherit these disorders, but at a lower rate than boys. The following choices give the genotypes for pairs of mothers and fathers. Which pair of parents could have a daughter with the recessive disorder a?
Choose one:a. XAXA × XAYb. XAXA × XaYc. XAXa × XAYd. XAXa × XaY

Answer 1

Answer:

d. $X^{A}X^{a}$ × $X^{a}Y$

Explanation:

Since the disorder is a recessive one, the daughter will need to inherit two recessive alleles, each one from the two parents in order for the disorder to manifest.

A cross between $X^{A}X^{a}$ and $X^{a}Y$ will yield the following offspring;

$X^{A}X^{a}$  female, carrier of disorder

$X^{a}X^{a}$ female, affected with disorder

$X^{a}Y$ male, affected with disorder

$X^{A}Y$ male, unaffected

Hence, the only parental pair that can have a daughter with the recessive disorder is $X^{A}X^{a}$ × $X^{a}Y$

The correct option is d.