Sally has brown hair, which is a dominant trait and is represented by B. But she carries the recessive gene of blond hair represented by b. Her husband Tom has blond hair, which is a recessive trait and represented by bb. What percentage of their children will have blond hair?

50% of their children will have blond hair

Explanation:

Given,

Allele for brown hair is represented by "B" and it is a dominant trait

While Allele for blond hair is represented by "b" and it is a recessive trait.

Genotype of Sally when it is given that she carries the recessive gene of blond hair - Bb

Genotype of Sally's husband who has has blond hair, which is a recessive trait - bb

Bb x bb

Bb, Bb, bb, bb

Out of four offspring two will have blonde color hair,

Thus, 50% of their children will have blond hair