American Masters | Clip | DNA Discoveries Before Watson and Crick

James Watson and Francis Crick discovered DNA’s structure in 1953, but other scientists paved the way for them. Swiss chemist Friedrich Miescher isolated DNA in 1869, testing cell nuclei in pus. In 1944, Oswald Avery, Colin MacLeod and Maclyn McCarty’s study of pneumonia bacteria provided definitive evidence that DNA was the molecule of heredity.