Question

Red eye color in fruit flies is dominant over white eyes. If eye color is X-linked,
what results do you expect to see if you cross a true-breeding red-eyed female
(genotype: XW+/XW+) with true-breeding a white-eyed male (XW/Y)?
Select one:
a. All offspring will have white eyes.
b. 100% of females will have red eyes, 0% of males will have red eyes.
c. All offspring will have red eyes.
d. 50% of females will have red eyes, 50% of males will have red eyes.

Answer 1

Answer:

C All fruit flies have red eyes.

Explanation:

See the image below

Since R (red) is dominant over r (white), then every fruit fly with R will have red eyes.

(The genotypic ratio indicate that 2 of the 4 boxes are XRXr and the other 2 boxes are XRY. While the phenotypic ratio indicate that 2 of the 4 boxes are red eye females and the other two boxes are red eye males. And since there's only 2 females and 2 males in total, everyone have red eyes.)