Painter, Theophilus Shickel
PAINTER, THEOPHILUS SHICKEL
(b. Salem, Virginia, 22 August 1889; d. Fort Stockton, Texas, 5 October 1969)
Painter is best known for introducing the use of the giant salivary gland chromosomes of the fruit fly, Drosophila melanogaster, into cytogenetic studies. With this material he was able to demonstrate in 1933 what until then had been only an assumption: that Mendelian genes could be identified with specific bands on physical structures in cell nuclei, the chromosomes.
The son of the Reverend Franklin Verzelius Newton Painter, professor of modern languages at Roanoke College, Virginia, and Laura Shickel, Painter received his early education from tutors. He entered Roanoke College in 1904 and received the B.A. in 1908. He then went to Yale on a fellowship in chemistry but soon found biology more to his liking. Working under A. Petrunkevitch and R. G. Harrison, Painter received the Ph.D. in 1913, then studied during 1913–1914 under Theodor Boveri at Würzburg. Returning to Yale in 1914, he served as an instructor in zoology for two years (1914–1916); during the summers of 1914 and 1915 he was an instructor in the invertebrate zoology course at the Marine Biological Laboratory, Woods Hole, Massachusetts. In 1916 he accepted a post as adjunct professor of zoology at the University of Texas, beginning a long and distinguished association with that university. In 1922 he was promoted to full professor and in 1939 became a distinguished professor in the graduate school. From 1944 to 1946 he was acting president of the university and from 1946 until 1952 was president. In 1952 he resigned the presidency to return to fulltime teaching and research. In 1966 he retired but continued his research and participated regularly in graduate seminars until his death.
By the 1930’s most geneticists were convinced that Mendel’s genes had an actual physical existence and were arranged in a linear fashion on the cell’s chromosomes (the common analogy was to beads on a string). At that time, however, there was no direct proof for the validity of this assumption. The linkage maps for Drosophila prepared by T. H. Morgan, C. B. Bridges, and their associates between 1915 and 1925 were only formalisms derived almost wholly from analysis of crossover frequencies (that is, breeding data). Positions on these maps represented only relative distances between the various genes. Several studies in the 1920’s had suggested that a point-by-point correspondence between linkage maps and the structure of actual chromosomes could be determined. In 1929, however, Painter and H. J. Muller (both at the University of Texas) cast doubt on this idea by showing that while the linear sequence determined by crude cytological methods and that determined by crossover data were the same, the spatial correspondences were not. That is, there appeared to be long areas of the chromosome in which no crossovers occurred, and other, shorter areas where a great deal seemed to occur.
The major problem in determining the correspondence between linkage maps and the structure of chromosomes was the small size of the latter. Workers before the 1930’s studied various types of somatic (body) or oögonial cells, in which the chromosomes were so small that detailed observation, particularly of the banding pattern, was impossible. Larger chromosomes had been observed in the 1880’s and, in the 1920’s, in salivary gland cells of young larval dipterans; but these cells had been found difficult to work with and observational studies with them had not been carried very far. In 1930 Painter found that if older larvae (almost ready to pupate) were used, large and easily observable chromosomes could be obtained. They offered ideal material for the study of small chromosomal segments and thus for the detection of modifications of chromosomal structure that could be correlated with variations in linkage maps. Painter’s paper of December 1933 established a method that made possible the detailed analysis of Drosophila and other insect chromosomes and provided the long-awaited confirmation of the chromosomal theory of heredity—the idea that genes are located on chromosomes.
In addition to studying the chromosomes of insects, Painter pioneered in the structural analysis of human chromosomes. He provided new techniques for studying human karyotypes (the full complement of chromosomes from a species, observed in squash or other preparations) and suggested ways of relating chromosomal aberrations to disease. He was also interested in the relationship of heterochromatin and chromosome puffing to ribonucleic acid (RNA) synthesis, and at the time of his death he was studying the nucleic acids found in the royal jelly of the honeybee. It was Painter’s original count of the human karyotype, in 1929 and subsequently, that established the erroneous total of 48 chromosomes (rather than 46), believed for many years to be the actual number for the human species.
Painter was a member of the U.S. National Academy of Sciences (1938), the American Philosophical Society (1939), the American Society of Zoologists, the American Genetics Society, the American Society of Naturalists, and Sigma Xi. He received the David Girard Elliott Medal of the National Academy of Sciences (1934) in recognition of his work on the giant chromosomes of Drosophila, and the M. D. Anderson Award from the University of Texas, for his “scientific creativity and teaching” (1969). He was also awarded an honorary D.Sc. from Yale (1936) and an LL.D. from Roanoke College (1942).
In 1917 Painter married Anna Mary Thomas, whom he had met at Woods Hole in 1914. They had four children.
Painter’s last scientific publication, “The Origin of the Nucleic Acid Bases Found in the Royal Jelly of the Honeybee,” appeared posthumously in Proceedings of the National Academy of Sciences…,64 (Sept. 1969), 64–66. His major work on the giant salivary gland chromosomes in Drosophila is “A New Method for the Study of Chromosome Rearrangements and Plotting of Chromosome Maps,” in Science,78 (1933), 585–586.
No full-scale biographical study exists, although presumably one will be issued by the National Academy of Sciences. My major sources of information have been a brochure from the University of Texas, announcing the M. D. Anderson Award in 1969 (supplied by Mrs. T. S. Painter), and several personal communications from Mrs. Painter in 1970.
Garland E. Allen