François Jacob, Lysogeny, and the Development of the Operon Model

This article summarizes the fundamental contribution of Francois Jacob in the field of molecular biology. Jacob was one of the handful of scientists who initiated the revolution in biology that took place in the second half of the 20th century. In their landmark publication of 1961, entitled "Genetic Regulatory Mechanisms in the Synthesis of Proteins", François Jacob and Jacques Monod presented a model for the regulation of gene expression deduced from genetic and biochemical studies. They proposed that a new class of genes, regulatory genes, would code for repressors that bind to operator sequences upstream of operons. The impact of the operon model was great: gene expression varies constantly and is under the direct control of proteins, two ideas that were revolutionary at the time they were proposed. It was also rapidly shown that in most organisms, except bacteria, co-regulated genes are not usually grouped together on the genome.