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.
