French biochemist who, with François Jacob (1920– ), first proposed the concept of a functional gene cluster (operon) to explain how gene expression is regulated in microorganisms. For this work they were awarded the 1965 Nobel Prize for Physiology or Medicine.
Monod was born in Paris and graduated in science from the University of Paris in 1931, receiving his doctorate ten years later. He was appointed assistant professor of zoology (1934–45), during which time he spent a year at the California Institute of Technology working under the geneticist T. H. Morgan. During World War II he fought in the French Resistance and in 1945 joined the Pasteur Institute, becoming head of the cellular biochemistry department (1954) and ultimately its director in 1971.
Working with the bacterium Escherichia coli, Monod and Jacob investigated the genes that code for three enzymes required by the bacterium to utilize the sugar lactose, and in 1961 they proposed a cluster (operon) comprising five neighbouring genes – a regulator, an operator, and three structural genes. The regulator gene codes for a repressor protein. In the absence of lactose in the medium, this repressor binds to the adjacent operator gene, preventing transcription of the three structural genes. However, if present in the medium, lactose (acting as an inducer) binds to the repressor molecule so removing it from the operator and allowing transcription to proceed. Many examples of operons have been found in bacteria but not in higher organisms.
Monod's best-selling Le Hazard et la necessité (1970; translated as Chance and Necessity, 1971) expounded his belief that life arose from a chance assembly of molecules and is directed only by the forces of natural selection. Man alone must ‘choose between the kingdom and the darkness’.
Subjects: Contemporary History (Post 1945).