white, abbreviated w, was the first sex-linked mutation discovered, found in the fruit fly Drosophila melanogaster.

Upon crossing this male with wild-type female flies, they found that the offspring did not conform to the expectations of Mendelian inheritance.

Further experimental crosses led them to the conclusion that this mutation was somehow physically connected to the "factor" that determined sex in Drosophila.

The protein coded by the white gene functions as an ATP-binding cassette (ABC) transporter.

Drosophila melanogaster with the white eye mutation often experience an increased sensitivity to light and a decrease in visual acuity.