Question

The inheritance of eye color in Drosophila is controlled by genes on each of the fly's four chromosome pairs. One eye-color gene is on the fly's X chromosome, so the trait is inherited in a sex-linked manner. For this sex-linked trait, the wild-type (brick red) allele is dominant over the mutant vermilion (bright red) allele.
A homozygous wild-type female fly is mated with a vermilion male fly.

Predict the eye colors of F1 and F2 generations. (Assume that the F1 flies are allowed to interbreed to produce the F2 generation.)

all wild, all vermilion, 1/2 1/2, 3/4 1/4

F1 Females
F1 Males
F2 Females
F2 Males

Answer 1

Answer:

F1 Females  - all wild type

F1 Males  - all wild type

F2 Females  -  - all wild type

F2 Males - 1/2 wild type, 1/2 vermilion

Explanation:

The wild-type allele (Xᵛ⁺) is dominant over vermilion (Xᵛ), which is a sex-linked trait.

Female flies have two X chromosomes, male flies have one X and one Y chromosome.

A homozygous wild-type female fly (Xᵛ⁺Xᵛ⁺) is mated with a vermilion male fly (XᵛY).

The female parent can only produce Xᵛ⁺ gametes.

The male parent can produce either Xᵛ or Y gametes.

When gametes from both parents fuse, the F1 offspring will have the genotypes Xᵛ⁺Xᵛ (females with wild type eyes) and Xᵛ⁺Y (males with wild type eyes).

The F1 females can produce Xᵛ⁺ and Xᵛ gametes. The F1 males can produce Xᵛ⁺ and Y gametes.

When the F1 individuals interbreed, the gametes combine to give rise to the F2 offspring. The possible combination of gametes that will give the different genotypes and phenotypes in the F2 are:

• Xᵛ⁺Xᵛ⁺ females with wild type eyes
• Xᵛ⁺ Y males with wild type eyes
• Xᵛ Xᵛ⁺ females with wild type eyes
• Xᵛ Y males with vermilion eyes