When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?
A) The gene involved is on the Y chromosome.
B) The gene involved is on the X chromosome.
C) The gene involved is on an autosome, but only in males.
D) Eye color in flies is a multifactorial trait.

Question

Quizplus · Accepted Answer

The gene involved in determining eye color in flies is on the X chromosome. Since males only have one X chromosome, they will express whichever allele is present on that single chromosome. If the allele for white eyes is present on that X chromosome, the male will have white eyes. In contrast, females have two X chromosomes, so they can potentially have two different alleles for eye color.

When Thomas Hunt Morgan Crossed His Red-Eyed F1 Generation Flies