François Jacob is renowned for many scientific contributions, including the discovery that the genes of a bacterium are arranged in a ring. His findings concerning the reproductive behaviour of bacteria were also of great significance. He discovered how, in the presence of lactose, Eschericia coli synthesises the enzyme beta galactosidase which in turn hydrolyses lactose into glucose and galactose. Besides the structural genes that act as encoders for enzymes, there are also regulator genes which serve to encode a repressor that allows or prevents enzyme synthesis.

This model serves as a paradigm: messages transmitted by the genes are directly controlled by the gene substance DNA through the “loop-like” action of protein. These findings opened the vast field of genetically-transmitted diseases to biological and medical research.

For these discoveries, François Jacob shared the 1965 Nobel Prize for Physiology or Medicine with Jacques Monod and André Lwof. He was 45 years old.

François Jacob dedicated the second half of his scientific career to the study of genetically-transmitted diseases, using a new experimental model, the eucaryote, in order to study embryo development in mice and to explain teratocarcinoma. Although his experimental research — based on the hypothesis that cancer was caused by the deregulation of genetic messages — would ultimately fail, as have all other fundamental forms of cancer research to date, perhaps one of the sparks he lit will some day illuminate the mystery.

François Jacob is a member of the French Academy and of the Academy of Sciences.