Alfred H. Sturtevant

Sturtevant, Alfred H. (1891-1970) was an American geneticist and the first to discover the procedure for gene mapping. This ability to determine the positions of genes on a chromosome made possible the Human Genome Project, an attempt to identify and map the entire set of human chromosomes.

Alfred Henry Sturtevant entered Columbia University in New York City in 1908, already having a strong interest in genetics. There, he worked in the laboratory of geneticist Thomas Hunt Morgan, who was using fruit flies (Drosophila) to research heredity. Drosophila had been found to be an excellent subject for such study because their short lifespan and other attributes make the passing of hereditary traits easy to track.


Sturtevant's first achievement under Morgan was in measuring the relative distance between different genes, which he succeeded in doing by first calculating the frequency with which traits “crossed over.” This first occurrence of gene mapping proved that traits that occurred most frequently were linked to genes that were closest together. Sturtevant received his Ph.D. degree from Columbia in 1914.

While still at Columbia, Sturtevant also discovered the “position effect,” which proved that the placement of a gene on the chromosome determined its effect. Perfecting their techniques, Sturtevant and his colleagues were eventually able to map three of Drosophila 's four chromosomes, but the final one, incredibly small, remained a mystery. In 1951, Sturtevant had another success by mapping it himself.

From 1928 on, Sturtevant was at the California Institute of Technology, in Pasadena, where Morgan was establishing a biological sciences division. Sturtevant was the university's first genetics professor and in 1965 published A History of Genetics, a text that is still important today. Except for short periods as a visiting professor at several European and American universities, he remained at Caltech for the rest of his career and received the National Medal of Science in 1968 for his achievements.