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.
[6] His work exploited the giant polytene chromosomes in the salivary glands of Drosophila and other Dipteran larvae.
[7] Painter was elected to the United States National Academy of Sciences in 1938 and the American Philosophical Society in 1939.
[8][9] Painter joined the faculty at the University of Texas in 1916 and, except for military duty during World War I, stayed there his whole career.
[11] He had tried to count the tangled mass of chromosomes he could see under a microscope in spermatocytes in slices of testicle and arrived at the figure of 24.