- Person
- François Jacob
- Lived
- 1920–2013
- Field
- Molecular biology
- From
- French
The story
Every cell in a body carries the same genes, yet cells use them very differently, and a bacterium can change which proteins it makes as its surroundings change. In the 1950s nobody knew how a cell decided which genes to use. At the Pasteur Institute in Paris, François Jacob, a former Free French medical officer who had been badly wounded in Normandy in 1944, had been studying bacteria and the dormant viruses that hide inside them. In 1958 he noticed a striking parallel between his results and those of his colleague Jacques Monod, who was studying how the bacterium E. coli digests milk sugar.
E. coli makes the enzymes for using lactose only when lactose is present. Jacob and Monod worked out why. The genes for those enzymes sit together in a unit they called an operon, next to a stretch of DNA that acts as a switch. A separate regulator gene makes a repressor protein that sits on the switch and blocks the genes. When lactose arrives, a form of it binds to the repressor, which lets go, and the genes are read. When the sugar is used up, the repressor returns and the genes fall silent.
In 1961 they published the model, distinguishing structural genes, which carry the recipe for a protein, from regulatory genes, which decide when it is made. They also proposed that each gene’s instructions are carried to the cell’s protein factories by a short-lived messenger RNA, which Jacob helped to demonstrate that year with Sydney Brenner and Matthew Meselson. In 1965 Jacob, Monod and André Lwoff shared the Nobel Prize in Physiology or Medicine for discoveries concerning the genetic control of enzyme and virus synthesis.
Gene regulation has since grown into one of the largest fields of biology. It explains how a single fertilised egg develops into many kinds of cell, how cells respond to hormones and drugs, and how cancer can begin when growth genes are switched on at the wrong time. The lac operon switch itself became a standard tool for making bacteria produce useful proteins on demand.
Why it matters
The operon model gave biology its first understanding of how genes are controlled, knowledge now used to study development, cancer and inherited disease and to make bacteria produce medicines.
About François Jacob
Free French war hero and Pasteur Institute biologist who showed how genes are switched on and off and helped discover messenger RNA, the basis of mRNA medicine. Nobel Prize 1965.
More about François Jacob
Sources
- François Jacob, Biographical NobelPrize.org
- François Jacob (1920–2013) The Embryo Project Encyclopedia, Arizona State University
- François Jacob Wikipedia
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.