Practice question

Interaction yielding 13:3 ratio characterized as dominant suppression where dominant allele at suppressor locus prevents expression of dominant allele at hypostatic pigment locus. Epistatic suppressor S- yields suppressed phenotype despite functional color allele B- present, so genotypes S-B- 9 plus S-bb 3 plus ssbb 1 all similar suppressed, totaling 13, leaving only ssB- 3 expressing color, giving 13 suppressed :3 colored. This dominant inhibitor acting epistatically over hypostatic gene classic in white leghorn chicken feathers, certain grains, demonstrates regulatory suppression mechanism rather than substrate limitation, distinguished from other epistatic ratios.