Question

If a child has blonde hair and both of her parents have brown hair, what does that tell you about the allele for blonde hair?

Answer 1

Answer:

The blonde hair would be the recessive trait and both the parents must be heterozygous dominant.

For instance, let us consider B and b the alleles of the gene responsible for the color of the hairs.

B is the dominant allele which codes for the brown color whereas b is recessive allele which codes for blonde hairs.

The phenotype of both the parents is a brown color, that is, dominant trait. They genotype would be Bb.

The cross would produce offspring with three possible types of genotypes BB, Bb, and bb in the ratio 1:2:1.

The offspring with BB and Bb genotype would have brown hair color and the offspring with bb would have blonde hair color.

Answer 2

This shows that the allele for blonde hair was hte recessive gene and therefore that child has a type of  genetic mutation, just like any child with red hair and green eyes