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

The explanation is that the gene involved is on the X chromosome. Since males only have one X chromosome, if that X chromosome carries the white-eye allele, they will display the white-eye phenotype. Females, on the other hand, have two X chromosomes, so even if one carries the white-eye allele, they may still have a dominant red-eye allele on the other X chromosome and display the red-eye phenotype.

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