Alfred Sturtevant

Alfred Sturtevant was an American geneticist who, in 1911 while still an undergraduate working in Thomas Hunt Morgan laboratory, constructed the first genetic map of a chromosome, using the frequency with which different traits were inherited together in the fruit fly Drosophila melanogaster to infer the relative positions of the genes responsible for them along the chromosome. His method rested on the insight that genes located closer together on a chromosome are less likely to be separated by the crossing-over that occurs during the formation of egg and sperm cells, so that the rate of crossing-over between two genes could serve as a measure of the physical distance between them, a principle that remains foundational to genetic mapping. Sturtevant went on to make further contributions to genetics including identifying chromosomal inversions, describing the first known case of a single gene mutation affecting behavior, and analyzing unequal crossing-over. He earned his doctorate under Morgan at Columbia University in 1914 and spent most of his career at the California Institute of Technology from 1928 onward, where he led an influential genetics research group. He received the National Medal of Science in 1967 for his career-long contributions to genetics.