Thirteen vital contributions to a field tht is now a cornerstone of the life sciences: Gregor Mendel's rules of heredity, Thomas Hunt Morgan's detection of chromosomal gene location, George Beadle and Edward Tatum's "one gene, one enzyme" concept, Barbara McClintock's discovery of transposons, the acceptance of DNA as the basis of genetic information, James Watson and Francis Crick's double helix, Marshall Nirenberg's genetic code, the discoveries of RNA, restriction enzymes, RNA splicing and RNA interference, Alec Jeffreys' DNA identification technique, and the Human Genome Project.