In fruit flies, males are determined by the presence of an X and Y chromosome; females are determined by two X chromosomes. The gene for eye color is located on the X chromosome and is absent from the Y chromosome. The allele for white eyes is recessive and the allele for red eyes is dominant. If a red-eyed male is mated with a white-eyed female, what is the probability that their male offspring will be white-eyed?

Question

Quizplus · Accepted Answer

Since the gene for eye color is located on the X chromosome and males inherit their X chromosome from their mothers, all male offspring will inherit their X chromosome from the white-eyed female. Given that the white eye allele is recessive and present on the mother's X chromosome, and males only have one X chromosome, all male offspring will express the white-eyed phenotype.

In Fruit Flies, Males Are Determined by the Presence of an X