Theophilus Painter

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Theophilus Shickel Painter (August 22, 1889 – October 5, 1969) was an American zoologist known for his work in identifying genes in fruit flies (Drosophila). He did so by applying the incredible detail that had just been discovered to be visible in the giant polytene chromosomes in the salivary glands of Drosophila and other Dipteran larvae.

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. He was, in succession, associate professor, professor and distinguished professor of zoology. He served as acting president (1944-1946) and president (1946-1952) of the University of Texas and retired from active teaching in 1966.

Painter is also known for his early study of human chromosomes. In 1921 he first gave the number 24 for the count of human meiotic chromosomes. 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. "I feel confident that this is correct," he said. Others later repeated his experiment in other ways and agreed the number was 24. If there were 24 chromosomes in spermatocytes, there must be an equal number contributed by the female and the human chromosome number must be 48. For over 30 years nobody disputed this 'fact.'

Then in 1955 Joe Hin Tjio, using better techniques, looked at the chromosomes in human somatic cells and plainly saw 46 chromosomes. Together with Albert Levan, Tjio published this revolutionary finding in early 1956, and the human chromosome number was finally revised. The wonder of Painter's work is not that it was in error but that, given the almost indecipherable mass of chromosomes he examined, he came so very close to the correct human chromosome number.