Theophilus Painter

Theophilus Shickel Painter (August 22, 1889 – October 5, 1969) was an American zoologist best known for his work on the structure and function of chromosomes, especially the sex-determination genes X and Y in humans. He was the first to discover that human sex was determined by an X/Y heteromorphic chromosomal pair mechanism. He also carried out work in identifying genes in fruit flies (Drosophila). His work exploited the giant polytene chromosomes in the salivary glands of Drosophila and other Dipteran larvae. Painter was elected to the United States National Academy of Sciences in 1938 and the American Philosophical Society in 1939.