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Marshall Warren Nirenberg helped crack the genetic code, showing experimentally which sequences of RNA nucleotides correspond to which amino acids — the discovery that explained, at the molecular level, how genes actually build proteins. The work earned him a share of the 1968 Nobel Prize in Physiology or Medicine alongside Har Gobind Khorana and Robert Holley, and he and Khorana were jointly awarded Columbia University's Louisa Gross Horwitz Prize that same year.