Labrador retrievers may be black, brown, or golden in color (see the chapter opening photograph). Although each color may breed true, many different outcomes occur if numerous litters are examined from a variety of matings, where the parents are not necessarily true-breeding. The following results show some of the possibilities. Propose a mode of inheritance that is consistent with these data, and indicate the corresponding genotypes of the parents in each mating. Indicate as well the genotypes of dogs that breed true for each color.

(a) black x brown (b) black x brown (c) black x brown (d) black x golden (e) black x golden all black 1/2 black 1/2 brown 3/4 black 1/4 golden all black 4/8 golden 3/8 black (1) black x golden (g) brown x brown (h) black x black 1/8 brown 2/4 golden 1/4 black 1/4 brown 3/4 brown 1/4 golden 9/16 black 4/16 golden 3/16 brown