Question

A dominant gene B is responsible for the wild type body color of Drosophila, its recessive allele b produces black body color. A test cross of a wild type female gave 52 black and 58 wild type in the $F_1$. If the wild type $F_1$ females are crossed with black $F_1$ males, what would be the expected genotypic ratio in the $F_2$.

• A. Heterozygous wild : Homozygous black = 1:1
• B. Homozygous wild : Heterozygous black = 1:1
• C. Homozygous wild : Heterozygous wild : Homozygous black = 1:2:1
• D. All heterozygous black

Answer 1

The correct option is A Heterozygous wild : Homozygous black = 1:1

All wild type females produced by test cross of wild type female would be heterozygous if the ratio is approximately 1:1. So when F1 generation heterozygous wild type female is crossed with the homozygous black male, heterozygous wild and homozygous black types would be produced in the ratio of 1:1.

So the correct answer is option A "Heterozygous wild : Homozygous black = 1:1"