Jacques Monod in the context of "Indeterminism"

Regulation of gene expression, or gene regulation, includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are widely observed in biology, for example to trigger developmental pathways, respond to environmental stimuli, or adapt to new food sources. Virtually any step of gene expression can be modulated, from transcriptional initiation, to RNA processing, and to the post-translational modification of a protein. Often, one gene regulator controls another, and so on, in a gene regulatory network.

Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed. Although as early as 1951, Barbara McClintock showed interaction between two genetic loci, Activator (Ac) and Dissociator (Ds), in the color formation of maize seeds, the first discovery of a gene regulation system is widely considered to be the identification in 1961 of the lac operon, discovered by François Jacob and Jacques Monod, in which some enzymes involved in lactose metabolism are expressed by E. coli only in the presence of lactose and absence of glucose.

The lactose operon (lac operon) is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria. Although glucose is the preferred carbon source for most enteric bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of β-galactosidase. Gene regulation of the lac operon was the first genetic regulatory mechanism to be understood clearly, so it has become a foremost example of prokaryotic gene regulation. It is often discussed in introductory molecular and cellular biology classes for this reason. This lactose metabolism system was used by François Jacob and Jacques Monod to determine how a biological cell knows which enzyme to synthesize. Their work on the lac operon won them the Nobel Prize in Physiology in 1965.

Most bacterial cells including E. coli lack introns in their genome. They also lack a nuclear membrane. Hence the gene regulation by lac operon occurs at the transcriptional level, by controlling transcription of DNA.

François Jacob (French: [ʒakɔb]; 17 June 1920 – 19 April 2013) was a French biologist who, together with Jacques Monod, originated the idea that control of enzyme levels in all cells occurs through regulation of transcription. He shared the 1965 Nobel Prize in Medicine with Jacques Monod and André Lwoff.

Chance and Necessity: Essay on the Natural Philosophy of Modern Biology (French: Le Hasard et la Nécessité: Essai sur la philosophie naturelle de la biologie moderne) is a 1970 book by Nobel Prize winner Jacques Monod. Aimed at a general audience, the book describes the basic characteristics of life, reviews findings of modern biochemistry and molecular biology, and argues that life arose by blind chance guided by natural selection, could not have been predicted, and does not have a higher purpose. The author concludes that traditional philosophical or religious systems of value, explanation and meaning are untenable, and advocates for an "ethic of knowledge": committing to objectivity in the pursuit of knowledge.

According to the introduction, the book's title was inspired by a line attributed to Democritus, "Everything existing in the universe is the fruit of chance and necessity."