Chapter 4, Problem 8P

Two genes interact to produce various phenotypic ratios among ${\text{F}}_{\text{2}}$ progeny of a dihybrid cross. Design a different pathway explaining each of the ${\text{F}}_{\text{2}}$ ratios below, using hypothetical genes $\text{R}$ and $\text{T}$ and assuming that the dominant allele at each locus catalyzes a different reaction or performs an action leading to pigment production. The recessive allele at each locus is null (loss-of-function). Begin each pathway with a colorless precursor that produces a white or albino phenotype if it is unmodified. The ratios are for ${\text{F}}_{\text{2}}$ progeny produced by crossing wild-type ${\text{F}}_{\text{1}}$ organisms with the genotype $\text{RrTt}$.

$\frac{\text{9}}{\text{16}}$ dark blue: $\frac{\text{6}}{\text{16}}$ light blue: $\frac{\text{1}}{\text{16}}$ white

$\frac{\text{12}}{\text{16}}$ white: $\frac{\text{3}}{\text{16}}$ green: $\frac{\text{1}}{\text{16}}$ yellow

$\frac{\text{9}}{\text{16}}$ green: $\frac{\text{3}}{\text{16}}$ yellow: $\frac{\text{3}}{\text{16}}$ blue: $\frac{\text{1}}{\text{16}}$ white

$\frac{\text{9}}{\text{16}}$ red: $\frac{\text{7}}{\text{16}}$ white

$\frac{\text{15}}{\text{16}}$ black: $\frac{\text{1}}{\text{16}}$ white

$\frac{\text{9}}{\text{16}}$ black: $\frac{\text{3}}{\text{16}}$ gray: $\frac{\text{4}}{\text{16}}$ albino

$\frac{\text{13}}{\text{16}}$ white: $\frac{\text{3}}{\text{16}}$ green