Comb shape in chickens represents one of the classic examples of gene interaction. two gene pairs interact to influence the shape of the comb. the genes for rose comb ( r) and pea comb ( p) together produce walnut comb. the fully homozygous recessive condition ( rrpp) produces the single comb. assume that a rose-comb chicken is crossed with a walnut-comb chicken and the following offspring are produced: 17 walnut, 16 rose, 7 pea, 6 single. (a) what are the probable genotypes of the parents? (b) give the genotypes of each of the offspring classes.