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 support your answer.
Answer (2)
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
A couple with brown hair can have red-haired children if both parents carry the recessive allele for red hair. Using a Punnett square, we determine that the probability of having red-haired children is 25%. This aligns with the observed outcome of having three red-haired and two brown-haired children.
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