Solutions For An Introduction to Genetic Analysis Chapter 6 Problem 46P

The true genetic basis for the cross of true-breeding brown dogs with true-breeding white dogs is a modified ratio of 12:3:1. It shows that two independently assorting genes are involved. Here the white color blocks the expression of color of the other gene. When pure breeding dogs were mated, the F₁ generation would be heterozygous (W/w) with 3 black and 1 brown, in which black is dominant over brown (B/b). In F_2, the progeny are in the ratio of 12:3:1

W/W; B/B (White dog) X w/w; b/b (brown dog)

Parental generation W/W; B/B X w/w; b/b

↓

F₁ generation W/w; B/b (heterozygous) X W/w; B/b

F₂ generation