Thomas Hunt Morgan Demonstrates Sex-Linked Inheritance; that Genes are Carried on Chromosomes

Around 1908 American geneticist Thomas Hunt Morgan of Columbia University started working on the fruit fly Drosophila melanogaster, and with his students mutated Drosophila through physical, chemical, and radiational means. In his "Fly Room" he began cross-breeding experiments to find inherited mutations, but with no significant success for two years. Finally in 1909, a series of heritable mutants appeared, some of which displayed Mendelian inheritance patterns, and in 1910 Morgan noticed a white-eyed mutant male among the red-eyed wild types. When white-eyed flies were bred with a red-eyed female their progeny were all red-eyed. A second generation cross produced white-eyed males—a sex-linked recessive trait, the gene for which Morgan named white. In discovering sex-linked inheritance Morgan was the first to link the inheritance of a specific trait definitively with a particular chromosome, demonstrating that genes are carried on chromosomes.

Morgan, "Sex-Limited Inheritance in Drosophila," Science 32 (1910) 120-22.

J. Norman (ed) Morton's Medical Bibliography 5th ed (1991) no. 245.2.