Thomas Hunt Morgan

Thomas Hunt Morgan (1866-1945), American biologist and geneticist, who discovered how genes are transmitted through the action of chromosomes, confirming the laws of heredity (see Mendel's Laws) of the Austrian botanist Gregor Mendel and laying the foundation for modern experimental genetics.

Born in Lexington, Kentucky, and educated at the State College of Kentucky, Morgan studied embryology at Johns Hopkins University, where he received his Ph.D. in 1891. As professor of experimental zoology at Columbia University from 1904 to 1928, he was at first critical of Mendelian theory, which had not been physically demonstrated. Performing breeding experiments and cytological analyses on the vinegar fly, Drosophila melanogaster, Morgan and his graduate students Alfred Henry Sturtevant, Calvin Blackman Bridges, and Hermann Joseph Muller revealed that chromosomes behave very similarly to the ways in which Mendel believed genes segregate and become randomly assorted. Discovering also that genes for many character traits are arranged in a linear fashion on each chromosome, Morgan and his coworkers created linear chromosome maps in which each gene is assigned to a specific position. This work resulted in The Mechanism of Mendelian Heredity (1915), an influential book that was an important step in the development of modern genetics.

Morgan continued his experimental work, demonstrating in Theory of the Gene (1926) that genes are held together in different linkage groups, and that alleles (pairs of genes affecting the same trait) interchange, or cross over, in the same linkage group. In 1933 Morgan won the Nobel Prize for physiology or medicine.