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 both normal body color and normal eyes? A) 3 B) 50 C) 150 D) 450 E) 600

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Since the genes are on different chromosomes, they will assort independently according to Mendel's law of independent assortment. Both traits are dominant, so the F1 generation from true-breeding parents (one with normal traits and the other with recessive traits) will all have normal body color and normal eyes. In the F2 generation, the expected ratio for each trait is 3:1 (dominant to recessive). Therefore, for two traits, the expected ratio is 9:3:3:1. Since 9 out of 16 flies will have both dominant traits, and there are 800 flies in total, $800 \times \frac{9}{16} = 450$ flies are expected to have both normal body color and normal eyes.

In Drosophila, the Genes for Body Coloration and Eye Size