D? Freckles are small, spots of a skin pigment called melanin. Most fair-skinned, red-haired people have them. Freckles are controlled primarily by the MC1R gene. Freckles are a dominant trait: parents who have freckles tend to have children with freckles. Bill and Barb both have freckles. Yet of their four children, one child does not have freckles! What must be the genotypes of Bill and Barb?
A) BB and BB
B) BB and Bb
C) Bb and Bb
D) Bb and bb

Question

D? Freckles are small, spots of a skin pigment called melanin. Most fair-skinned, red-haired people have them. Freckles are controlled primarily by the MC1R gene. Freckles are a dominant trait: parents who have freckles tend to have children with freckles. Bill and Barb both have freckles. Yet of their four children, one child does not have freckles! What must be the genotypes of Bill and Barb?
 A) BB and BB 
 B) BB and Bb 
 C) Bb and Bb 
 D) Bb and bb