Ochoa, Severo, oh CHOH uh, say VAY roh (1905-1993), a Spanish-born American scientist, suceeded in producing a nucleic acid by artificial means. Nucleic acids are complex chemicals found in the cells of all living things that play vital roles in heredity and cell development. Ochoa's work led to understanding the processes by which nucleic acids are made in nature. For this work, Ochoa shared the 1959 Nobel Prize for physiology or medicine with American Arthur Kornberg.