Suppose that in humans the ability to roll the tongue (R) is dominant to being unable to roll it (r), and having freckles (F) is dominant to having no freckles (f). If a woman heterozygous for both traits married a man with no freckles who couldn't roll his tongue, what is the probability that they would have a freckled, tongue-rolling child?

1/4

Explanation:

A heterozygous woman for both traits (RrFf) marries with a man with no freckles (ff) who can't roll his tongue (rr).

The cross is: RrFf X rrff.

The woman can produce the gametes RF, Rf, rF and rf

The man can only produce rf gametes.

The possible offspring that can arise from the combination of those gametes is:

1/4 RrFf Freckled, tongue-rolling 1/4 Rrff Freckled, unable to roll tongue 1/4 rrFf Not freckled, tongue-rolling 1/4 rrff Not freckled, unable to roll tongue