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) Other male-specific factors influence eye color in flies.
E) Other female-specific factors influence eye color in flies.

Question

Quizplus · Accepted Answer

In fruit flies, eye color is determined by a gene on the X chromosome. Since males only have one X chromosome, they inherit the eye color gene from their mother. If the mother has the red-eye allele, then the male offspring will have red eyes. However, if the mother has the white-eye allele, then the male offspring will have white eyes since they do not inherit a second copy of the X chromosome to mask the effect of the white-eye allele. Females, on the other hand, have two X chromosomes and inherit one from each parent. This means that if they inherit the white-eye allele on one X chromosome, they can still have red eyes if they inherit the red-eye allele on the other X chromosome. Thus, both red- and white-eyed female offspring are possible.

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