Human hair color is a classic, if oversimplified, example of recessive epistasis. red hair is caused by a recessive allele r. however, if an individual has a dominant r allele, they may have either brown or blonde hair depending on whether they have a dominant b allele (which causes brown hair), or are homozygous for a recessive b allele (which causes blonde hair). the b and r loci are on located on different chromosomes. if a couple with genotypes bb; rr and bb; rr have children, what hair colors and in what proportions are expected among their children?