In chickens, comb shape is determined by alleles at two loci (r, r and p, p). a walnut comb is produced when at least one dominant allele r is present at one locus and at least one dominant allele p is present at a second locus (genotype r_ a rose comb is produced when at least one dominant allele is present at the first locus and two recessive alleles are present at the second locus (genotype r_ pp). a pea comb is produced when two recessive alleles are present at the first locus and at least one dominant allele is present at the second (genotype rr if two recessive alleles are present at the first and at the second locus (rr pp), a single comb is produced. a walnut is crossed with a pea chicken and the offspring consists of 3/8 walnut, 3/8 pea, 1/8 rose and 1/8 single. what are the probable genotypes of the parents