Morgan, Thomas Hunt

Thomas Hunt Morgan (1866-1945) was an American evolutionary biologist, geneticist and embryologist. He acquired a Nobel prize in Physiology or Medicine in 1933 for his work in establishing the chromosomal theory of inheritance.
==Biography==
Thomas Hunt Morgan was born on September 25, 1866, at Lexington, Kentucky, U.S.A.. He studied at the University of Kentucky, where he obtained his B.C. degree. He continued with his studies at the John Hopkins University. In 1891 he became an Associate Professor of Biology at Bryn Mawr College for Women. In 1904 he became Professor of Experimental Zoology at Columbia University, New York. He remained at Columbia University until 1928, when he was appointed Professor of Biology and Director of the G. Kerckhoff Laboratories at the California Institute of Technology, at Pasadena.? During his later years he had his private laboratory at Corona del Mar, California. Thomas H. Morgan died on December 4, 1945.
==Experiments in embryology:==
During the period 1893–1910, T. H. Morgan focused on fundamental problems in embryology such as the formation of embryos from separated blastomeres and fertilization in nucleated and nonnucleated egg fragments. In this time Morgan was very sceptical with the Darwinian Theory of evolution and didn' t believe the mechanism of natural selection. He had also objections towards Mendelian and chromosome theories.
==Work on Drosophila Melanogaster:==
===Chromosomal theory of inheritance:===
Morgan had become interested in species variation, and in 1911, he established the "Fly Room" at Columbia University to determine how a species changed over time. He observed a small variation in Drosophila, which is known as the "white-eye" in single male flies. He bred these white-eyed male flie with normal, red-eyed, females.
He observed that the F1 generation of offsprings was uniformed and all the fruitflies were red-eyed. The F2 generation on the other hand again contained white-eyed males, but all the females were red-eyed. Morgan therefore proposed a theory about sex-linked characters (which were part of the chromosome X). He started to describe these hereditary units as genes. Based on this knowledge he verified the Mendelian and chromosome theories. Morgan quickly developed the Drosophila work into a large-scale theory of heredity. A particularly important part of his work describes the fact, that each of the Mendelian genes can be assigned a certain possition on the linear chromosome.
===Genetic linkage and crossing-over:===
Based on experiments with multiple-mutants, Morgans hypothesized that the amount of crossing over between linked genes differs and that crossover frequency might indicate the distance separating genes on the chromosome.The unit of measurement of gene linkage is therefore called the morgan. Morgan's student Alfred Sturtevand based on these discoveries created in 1913 a first genetic map.
===References:===
biography: Nobel Prize.org
Work: Britannica
: Wikipedia
: Thomas Hunt Morgan and Sex Linkage, Ilona Miko, Nature (2008)