Operon

François Jacob and Jacques Monod, 1960

An operon is a functional unit of DNA, a section of DNA that contains, among other things, the information for the formation of a certain substance. Operons are mostly found in prokaryotes (e.g. bacteria), but also in some eukaryotes.

The functional unit of an operon consists of a promoter, operator(s) and several (structural) genes that code for proteins with typically related functions. Depending on the operon, various regulatory proteins can interact with the operators as repressors or activators. They thereby influence the transcription of the genes in the operon by switching them on or off. This functionality is controlled by ligands or effector molecules that are formed by the cell itself or are taken up by it. This can activate or inhibit the synthesis of the relevant mRNA (messenger RNA) and indirectly also the translation of the encoded proteins.

Operons also play an important role as tools for genetic engineering. Any gene can be placed under the control of the regulatory elements of an operon and can thus be specifically activated, e.g. in the case of the lac operon by adding the synthetic inducer IPTG (isopropyl-β-D-thiogalactopyranoside).