Chapter 5, Problem 4EQ

As a hypothetical example, a trait in mice results in abnormally long tails. You initially have a true-breeding strain with normal tails and a true-breeding strain with long tails. You then make the following types of crosses:

Cross 1: When true-breeding females with normal tails are crossed to true-breeding males with long tails, all ${\text{F}}_{\text{1}}$ offspring have long tails.

Cross 2: When true-breeding females with long tails are crossed to true-breeding males with normal tails, all ${\text{F}}_{\text{1}}$ offspring have normal tails.

Cross 3: When ${\text{F}}_{\text{1}}$ females from cross 1 are crossed to true-breeding males with normal tails, all offspring have normal tails.

Cross 4: When ${\text{F}}_{\text{1}}$ males from cross 1 are crossed to true-breeding females with long tails, half of the offspring have normal tails and half have long tails.

Explain the pattern of inheritance of this trait.