White (mutation)

"white" was the first sex-linked mutation ever discovered in "Drosophila melanogaster". In 1910 Thomas Hunt Morgan, (or, legend has it, his wife) collected a single male white-eyed mutant from a population of "Drosophila melanogaster" fruit flies, which usually have bright red eyes. Upon breeding this male with wild-type female flies he found that the offspring did not conform to the expectations of Mendelian inheritance. [ Morgan, TH: (1910) "Sex Limited Inheritance in Drosophila." "Science", 32(812):120-122] The first generation (the F1) produced 1,237 red-eyed offspring and three white-eyed flies, all males. The second generation (the F2) produced 2,459 red-eyed females, 1,011 red-eyed males, and 782 white-eyed males. Further experimental crosses led Morgan to the conclusion that this mutation was somehow physically connected to the "factor" that determined gender in Drosophila. Morgan named this trait "white", now abbreviated "w". [As the field of genetics developed, names for genes were italicized, and dominant alleles were capitalized while recessive alleles (such as "white") were made lower case. Names of commonly used mutations were shortened, and since "white" was one of the first named, it was shortened to a single letter.] Flies carrying the "white" allele are frequently used to introduce high school and college students to genetics. White-eyed flies are blind.

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