François Jacob

François Jacob, born in 1920, French biologist and Nobel laureate. Jacob studied how deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) transfer genetic information (see Genetics) and researched the genetic control of embryonic growth (see Embryology). For his work on genetic control of enzymes and virus synthesis he was awarded the 1965 Nobel Prize in physiology or medicine, which he shared with French biologists Jacques Monod and Andre Michel Lwoff.

Jacob was born in Nancy, France. He was studying medicine at the University of Paris in 1940 when the German Army invaded France but was able to escape to England. He joined the Free French forces and fought with the Allied forces in North Africa and Normandy (Normandie). After World War II (1939-1945) Jacob returned to the University of Paris where he completed his medical degree in 1947. He then decided to pursue research rather than medical practice and went on to earn a B.S. degree in biology in 1951 and a D.Sc. degree in biology in 1954, both from the University of Paris. Since 1950 Jacob has been affiliated with the Pasteur Institute in Paris. He was appointed head of the institute's laboratory in 1956 and head of its Department of Microbial Genetics in 1960. In 1964 he was also named a professor of the College de France in Paris.

In 1961 Jacob and his Pasteur Institute colleague Monod described the operon model of gene regulation in one of the milestone papers of molecular biology. The operon model explains how cells manage to control the activities of their genes by turning them on and off at the appropriate times. Jacob and Monod distinguished two kinds of genes: structural and regulatory. The regulatory gene, essentially a switch that is turned on or off in response to local conditions, controls the related structural gene that transmits an organism's DNA, or hereditary material. Jacob and Monod saw in their model an explanation for why some cancers caused by viruses are activated after being dormant in the body. Under stable conditions, regulatory genes repress structural genes, but a disturbance can cause the regulatory genes to turn on the structural genes, thus initiating replication, or copying, of the DNA. Such replication, when uncontrolled, is cancer. Jacob and French bacteriologist Elie Wollman, also of the Pasteur Institute, showed that genetic recombination and replication occur in a similar manner in both bacteria and in humans.