Chapter 4, Problem 17P

The coat color in mink is controlled by two codominant alleles at a single locus. Red coat color is produced by the genotype ${\text{R}}_{\text{1}}{\text{R}}_{\text{1}}$, silver coat by the genotype ${\text{R}}_{\text{1}}{\text{R}}_{\text{2}}$, and platinum color by ${\text{R}}_{\text{2}}{\text{R}}_{\text{2}}$. White spotting of the coat is a recessive trait found with the genotype ss. Solid coat color is found with the S– genotype.

a. What are the expected progeny phenotypes and proportions for the cross Ss ${\text{R}}_{\text{1}}{\text{R}}_{\text{2}}$ * ss ${\text{R}}_{\text{2}}{\text{R}}_{\text{2}}$?

b. If the cross Ss ${\text{R}}_{\text{1}}{\text{R}}_{\text{2}}$ * Ss ${\text{R}}_{\text{1}}{\text{R}}_{\text{1}}$ is made, what are the progeny phenotypes, and in what proportions are they expected to occur?

c. Two crosses are made between mink. Cross $\text{1}$ is the cross of a solid, silver mink to one that is solid, platinum. Cross $\text{2}$ is between a spotted, silver mink and one that is solid, silver. The progeny are described in the table below. Use these data to determine the genotypes of the parents in each cross.