PASADENA, Calif.--Norman Horowitz, a geneticist best known for his work on the "one-gene, one-enzyme" hypothesis and the experiments aboard the Viking lander to search for life on Mars in 1976, died on Wednesday, June 1, at his home in Pasadena. He was 90.
A pioneer of the study of evolution through biochemical synthesis, Horowitz was a professor of biology at the California Institute of Technology for many years. After a distinguished career studying the genetics of the red bread-mold Neurospora crassa, he began collaborating with the Jet Propulsion Laboratory in 1965 after becoming interested in the biochemical evolution of life and its possible applications to the search for life on other worlds. He spent five years as chief of JPL's bioscience section.
Horowitz was a member of the scientific teams for both the Mariner and Viking missions to Mars. On the Viking mission, he and two collaborators designed an instrument capable of detecting any biochemical evidence of life on the planet. The results of the experiment were negative at the two Viking sites, but this information in itself was a robust scientific result that continues to inform current efforts in astrobiology to this day.
Horowitz is most renowned in the field of biochemistry for his 1945 thought experiment on biochemical evolution. The paper, published in the Proceedings of the National Academy of Sciences, is today considered the origin of the study of evolution at the molecular level. Horowitz also performed a seminal experiment that led to the widespread acceptance of the one-gene, one-enzyme hypothesis that, until the early 1950s, was considered a radical theory of the way that life carries on its chemistry. Horowitz and a colleague used mutations to disprove an alternative interpretation that was gaining credence at the time, thereby indirectly strengthening the one-gene, one-enzyme hypothesis.
A native of Pittsburgh, Horowitz earned his bachelor's degree at the University of Pittsburgh, and then came to Caltech in 1936 for graduate study in the comparatively new division of biology, founded by famed geneticist Thomas Hunt Morgan. After completing his doctorate in 1939 under embryologist Albert Tyler, Horowitz became a postdoctoral researcher at Stanford University, in the laboratory of George W. Beadle.
When Beadle became chair of the Caltech biology division in 1946, Horowitz returned to his alma mater as a faculty member, and stayed at the Institute for the remainder of his career. He was the biology division chair from 1977 to 1980, and became a professor emeritus in 1982. His contributions to the division also included the endowment of the Horowitz Lecture Series.
He was a member of the National Academy of Sciences and the American Academy of Arts and Sciences. His honors included a 1998 medal from the Genetics Society of America. He was also the author of a 1986 book titled To Utopia and Back: The Search for Life in the Solar System.
Horowitz is survived by a daughter, Elizabeth Horowitz of Berkeley, and a son, Joel Horowitz of Iowa City, Iowa and Evanston, Illinois. He has two grandchildren, Katharine of Minneapolis, Minnesota, and Daniel of Davis, California. He was married to Pearl (née Shykin) Horowitz, who died in 1985. Horowitz funded the Pearl S. Horowitz Book Fund at Caltech in her honor.
