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

d.
`X^(A)X^(a)` ×
`X^(a)Y`

Step-by-step 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.