François Jacob, Andre Michael Lwoff, and Jacques Lucien Monod Biography

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World of Scientific Discovery on François Jacob, Andre Michael Lwoff, and Jacques Lucien Monod

Jacob, Lwoff, and Monod are best known for their explanation of gene expression; that is, whether a gene is "on" and its instructions are carried out by the cell's ribosomes, or whether it is "off" and ignored. For their work, they received the 1965 Nobel Prize for physiology or medicine.

François Jacob was born in June 1920 in Nancy, Meurthe-et-Moselle, France. He intended to be a surgeon, but injuries he sustained during World War II prevented this, and he switched to research. He received his M.D. in 1947 from the University of Paris and his Doctor of Science in 1954 from the Sorbonne. He then joined the faculty of the Pasteur Institute, becoming head of the Department of Cellular Genetics in 1960. He became a professor of cellular genetics at the College de France in 1964.

Andre Lwoff was born on May 8, 1902, in Ainay-le-Château, Allier, France. After undergraduate studies and a brief period in medical school, he went into laboratory work at the Pasteur Institute in 1921. He eventually obtained medical and doctoral degrees. Active in the underground Resistance during World War II, he became professor of microbiology at the University of Paris in 1959 and headed the Cancer Research Institute in Villejuif in 1968.

Jacques Monod was born on February 9, 1910, in Paris. His scholarly father encouraged Monod's interest in biology, and from his secondary teachers, he developed a love for the arts. His mother was an American. Monod graduated from the University of Paris in 1931, joined its faculty in 1934, and received his doctorate there in 1941. After World War II, while active in the underground Resistance, Monod joined the Pasteur Institute.

The three researchers based their work on the findings of American geneticist George Wells Beadle that gene-directed enzymes affect biochemical processes. Jacob's experiments with E. coli showed that the medium in which the bacteria are grown affects the type and amount of enzymes the bacteria produce (induction). From this, the three scientists proposed that the bacteria regulate enzyme production. If grown in the sugar glucose, the bacteria produce very little of the enzyme -galactosidase, because they do not require it for metabolizing glucose. But if they grow in lactose, E. coli bacteria produce much more -galactosidase, which they need to metabolize lactose.

To explain how the bacteria regulate enzyme production, the scientists theorized that there are three types of genes, a gene being a deoxyribonucleic acid (DNA) triplet or triplet cluster. An operon is a gene cluster composed of two types of genes: Z (structural) genes, which carry the instructions for protein production, such as for the -galactosidase, and O (operator) genes, which control whether the Z genes' instructions are carried to the cell's ribosomes for protein production. The third type, called R (regulator) genes, instruct production of proteins that control the activity of other genes. In E. coli, when lactose is not present, an R gene instructs production of a repressor protein that binds to the O gene, turning the gene "off" by preventing it from being copied by ribonucleic acid (RNA). When lactose is present, the repressor binds to it rather than the O gene. This allows the O gene to turn the Z gene "on." Research showed the theory to be correct.

Andre Lwoff is noted for other research as well. He discovered that, in some protozoa, genes are expressed outside of the cell nucleus as well as within it. He showed how viral DNA incorporates itself into bacterial DNA so that it is replicated when the bacterial cell prepares to divide. He also showed that ultraviolet radiation changes passive viral DNA into an active state within its bacterial host. His numerous honors include membership in the National Academy of Sciences of the USA. Lwoff died in 1994.

Jacques Monod is also known for his 1970 book Chance and Necessity, which showed by biochemical evidence how all life, including human, stems from the random chance of mutation and the necessity of Darwinian natural selection. Monod died in 1976.