Travel and Academics

In 1891, Morgan took up the position of a professor of biology at Bryn Mawr College, after which he went to Europe for further studies. He went first to Germany and then to Naples, Italy where he studied at the famous zoological station. He met Hans Driesch, the philosopher scientist who believed in vitalism. Morgan, however, favoured a mechanistic view of biological problems. Morgan returned to the United States in 1904 and accepted a professorship at Columbia University, which he continued till 1928. It was during this period that Mendel’s law of inheritance was rediscovered and re-examined and the science of genetics began to establish itself.

Chromosome Theory

While at Columbia University, Morgan undertook a series of experiments on breeding to assess the role of genes in heredity. He chose the fruit fly (Drosophila–melanogaster) for his experiments because it had a short life cycle and could be bred in the laboratory itself. It multiplied in no time and its cells possessed only four pairs of chromosomes. By following the generations he discovered numerous cases of mutations which he crossbred with normal ones. The percentages of normal and mutant offsprings were in accordance with Mendel’s Law of Inheritance. Morgan showed that the various characteristics were indeed linked, that is inherited together as though the genes involved occurred on the same chromosome. From this he postulated that all sex-linked characters were associated as a unit on a single chromosome in the nucleus of the original cell. He called these characters linkage groups. Morgan used the term gene to represent each character unit. He also discovered that genes are positioned on a single line on chromosomes. By 1911, the first chromosome maps for fruit flies were drawn up. In 1915, Morgan and his assistants published The Mechanism of Mendelian Heredity to describe the system of genes. His book "Theory of the Gene (1926)", established, extended and completed the Mendelian system as far as the eye and the microscope could carry it. It would be another quarter of a century before molecular biology, advanced by men like Crick and Watson would carry genetic research a step further.

In 1941, Morgan retired as head of his department at California Institute of Technology. But he continued work on embryology and tried to find out why spermatozoon of the common sea squirt (hermaphroditic–containing both sperm and eggs) never fertilized its own egg but fertilized eggs of all other sea squirts. Morgan died on December 4, 1945 at Pasadena California.

Thomas Hunt Morgan was born on September 25, 1866, in Lexington, Kentucky to Charlton and Ellen Morgan. He was descended on both sides from English Cavalier stock. He entered the State College of Kentucky in 1886, and later studied at John Hopkins University where he took up both physiology and morphology. In 1890, he received his doctorate for a paper on the embryology and phylogeny of sea spiders.

Morgan’s chromosome theory of heredity was the most outstanding biological principle advanced since Darwin’s theory of evolution and Mendel’s preliminary Law of Inheritance. His theory provided a physical basis to Mendel’s generic theory and opened out possibilities of controlled evolution that was later introduced by Hermann J. Muller. The future role of genetics in the field of was also considerably enchanted as a result of Morgan’s pathbreaking discovery. He was awarded the Nobel Prize in physiology and Medicine in 1933 for his significant contribution in establishing the new genetics, that was to revolutionise man’s understanding of biological behaviour.

Morgan was driven by an incessant curiosity to find out the exact role of genes in the perpetuation of hereditary characteristics. Blessed with sharp analytical abilities, he devised his own experimental methods to find an answer to an age old and vexing questions. His power of observation and his crusading zeal was so great that he was known as the Grand Old Man of genetics – a man who advanced the cause of genetics immensely for future mankind. He founded the Kerckoff Laboratories of Biological Sciences at the California Institute of Technology that became a Mecca for all genetic scientists world over.