Monod

Jacques Lucien Monod (1910–1976) was a French biologist and a key figure in the founding of molecular biology. He shared the 1965 Nobel Prize in Physiology or Medicine with François Jacob and André Lwoff for discoveries concerning the genetic control of enzyme and virus synthesis.

In his collaboration with Jacob and Lwoff, Monod helped establish the operon model of gene regulation in bacteria, most famously illustrated by the lac operon in Escherichia coli. The model posits that a set of genes is regulated as a unit by a shared regulatory mechanism, allowing cells to respond to environmental changes. Monod and his colleagues demonstrated that gene expression could be induced or repressed, depending on the presence of regulatory proteins and small molecule effectors such as inducers and repressors, laying the foundation for understanding transcriptional control in living cells. He also contributed to the concepts of catabolite repression and the idea that regulation occurs at the level of enzyme synthesis.

Monod also formulated mathematical descriptions of microbial growth, most notably the Monod equation, mu = mu_max · S/(K_s + S), which relates growth rate to substrate concentration. In structural biochemistry, the Monod–Wyman–Changeux model of allostery described how proteins switch between active and inactive forms in response to ligand binding.

Beyond his experimental work, Monod authored Chance and Necessity (1970), a concise philosophical treatise arguing that life is shaped by chance and constrained by necessity. His work influenced microbiology, genetics, and philosophy of biology. The Institut Jacques Monod in Paris is named in his honor, reflecting his impact on the field.