In Drosophila, the genes for body coloration and eye size are on different chromosomes.Normal-colored bodies are dominant to ebony-colored (very dark) bodies, and normal-sized eyes are dominant to eyelessness.Line A is true breeding for normal bodies and normal eyes, whereas line B is true breeding for ebony bodies and eyelessness.From an F₂ cross between lines A and B, 800 flies are scored.How many F₂ flies are expected to have normal body color and to be eyeless?

Question

Quizplus · Accepted Answer

From the cross F₂, the expected ratio is 1:1:1:1 for normal body:normal body & eyeless:ebony body:ebony body & eyeless. Thus, out of 800 flies, 200 are expected to be normal body & eyeless. Therefore, the number of F₂ flies expected to have normal body color and to be eyeless is 1/4th of 200 which is 50. Therefore, the best choice is (C) 150.

In Drosophila, the Genes for Body Coloration and Eye Size