Alfred Henry Sturtevant  was an American geneticist. Sturtevant constructed the first genetic map of a chromosome in 1913. Alfred Henry Sturtevant was on November 21, 1891 born in Jacksonville, Illinois. Sturtevant was always interested in inheritance and genetics. Sturtevant received his Ph.D. degree from Columbia in 1914. He received the National Medical of Science in 1967 for his work on Drosophila genetics. 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 to research heredity. 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. He died on April 5, 1970 (aged 78).