Question

In humans, the allele for red hair, b, is recessive to the allele for brown hair, B. A man and his wife both have brown hair. They have five children, three of whom have red hair, while two have brown hair. Explain how this may happen, using a genetic diagram to explain your answer.

Answer 1

We know that the parents express as brown haired which means that they may have the genotypes BB and Bb. We know that for the children to express as red-haired, they must have two recessive genes. Because they get one gene from each parent, both parents must have one recessive gene.

      B     b
B   BB   Bb
b   Bb    bb