Chapter 3, Problem 19P

Four eye-color mutants in Drosophila—apricot, brown, carnation, and purple—are inherited as recessive traits. Red is the dominant wild-type color of fruit-fly eyes. Eight crosses (A through H) are made between parents from pure-breeding lines.

a. Which of these eye-color mutants are X-linked recessive and which are autosomal recessive? Explain how you distinguish X-linked from autosomal heredity.

b. Predict F₂ phenotype ratios of Crosses A, B, D, and G.