Can Female Flies Have White Eyes?

The white eye gene in fruit flies is located on the X chromosome. It is one of many sex-linked genes. Most are on the X chromosome, which is larger than the Y chromosome. Thomas Hunt Morgan first discovered the gene when he was studying the inheritance of eye color in fruit flies. However, the white eye gene is rare in natural populations. Females generally have red eyes.

Morgan’s first attempt to reproduce the white eye gene in female flies proved to be unsuccessful. The first test crossed a white-eyed male with a red-eyed female. This proved that the trait is X-linked. Females with two copies of the gene will develop the white eye phenotype.

The red-eyed flies have a red-eyed allele at the Near marker, while the white-eyed female flies carry the yellow-eyed allele at the far marker. The blue allele is located in close proximity to the eye color gene and “hitchhikes” with the red eye allele.

Morgan used his experiments to test the theory and he observed that the red-eyed female had a mutation in the fly eye color gene. These results led him to conclude that this gene was present on the X chromosome. Later, Calvin Bridges confirmed this by showing that the sex chromosomes do not separate during meiosis.