operon


operon
/op"euh ron'/, n. Genetics.
a set of two or more adjacent cistrons whose transcription is under the coordinated control of a promoter, an operator, and a regulator gene.
[1960-65; < F opéron, equiv. to opér(er) to work, OPERATE + -on -ON1]

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Genetic regulatory system of single-celled organisms (prokaryotes) and their viruses, in which genes coding for functionally related proteins are clustered along the DNA, enabling their expression to be coordinated in response to the cell's needs.

By providing a means to produce proteins only when and where they are required, the operon allows the cell to conserve energy. A typical operon consists of a group of structural genes that code for enzymes involved in a metabolic pathway, such as the biosynthesis of an amino acid. A single unit of messenger RNA is transcribed from the operon and is then translated into separate proteins. Operons are controlled by various regulatory elements that respond to environmental cues. The operon system was first proposed by François Jacob and Jacques Monod in the early 1960s.

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      genetic regulatory system found in bacteria and their viruses in which genes coding for functionally related proteins are clustered along the DNA. This feature allows protein synthesis to be controlled coordinately in response to the needs of the cell. By providing the means to produce proteins only when and where they are required, the operon allows the cell to conserve energy (which is an important part of an organism's life strategy).

      A typical operon consists of a group of structural genes that code for enzymes involved in a metabolic pathway, such as the biosynthesis of an amino acid. These genes are located contiguously on a stretch of DNA and are under the control of one promoter (a short segment of DNA to which the RNA polymerase binds to initiate transcription). A single unit of messenger RNA (mRNA) is transcribed from the operon and is subsequently translated into separate proteins.

 The promoter is controlled by various regulatory elements that respond to environmental cues. One common method of regulation is carried out by a regulator protein that binds to the operator region, which is another short segment of DNA found between the promoter and the structural genes. The regulator protein can either block transcription, in which case it is referred to as a repressor (repression) protein; or as an activator protein it can stimulate transcription. Further regulation occurs in some operons: a molecule called an inducer can bind to the repressor, inactivating it; or a repressor may not be able to bind to the operator unless it is bound to another molecule, the corepressor. Some operons are under attenuator control, in which transcription is initiated but is halted before the mRNA is transcribed. This introductory region of the mRNA is called the leader sequence; it includes the attenuator region, which can fold back on itself, forming a stem-and-loop structure that blocks the RNA polymerase from advancing along the DNA.

      The operon theory was first proposed by the French microbiologists François Jacob (Jacob, François) and Jacques Monod (Monod, Jacques) in the early 1960s. In their classic paper they described the regulatory mechanism of the lac operon of Escherichia coli, a system that allows the bacterium to repress the production of enzymes involved in lactose metabolism when lactose is not available.

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Universalium. 2010.

Look at other dictionaries:

  • Operon — Opéron Un opéron est un groupement de gènes et de séquences régulatrices du génome des procaryotes chez qui cette organisation est principalement rencontrée. Les gènes concourent à la réalisation d une même fonction physiologique et sont… …   Wikipédia en Français

  • opéron — [ ɔperɔ̃ ] n. m. • 1961; de opérer ♦ Biol. Ensemble de gènes contigus sur le chromosome, dont les fonctions sont reliées et qui est une unité coordonnée de transcription régulée par un effecteur protéique. ● opéron nom masculin Groupe de gènes de …   Encyclopédie Universelle

  • operon — OPERÓN s.m. (biol.) Amsamblu de gene structurale a căror expresie fenotipică este controlată de un operator; unitate genetică a cărei expresie fenotipică este reglată de un represor. [< fr. opéron, it. operone]. Trimis de LauraGellner,… …   Dicționar Român

  • operon — operon. См. транскриптон. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • operón — (en biología molecular) segmento de ADN formado por un gen operador y uno o más genes estructurales con funciones relacionadas, controlado por el gen operador junto con un gen regulador. Diccionario ilustrado de Términos Médicos.. Alvaro Galiano …   Diccionario médico

  • Operon — Operon, mehrere Strukturgene umfassende Funktionseinheit in Protocyten, die ein gemeinsames mRNA Molekül bildet, deren Gene also entweder alle aktiv oder inaktiv sind und die unter der Kontrolle eines ⇒ Operators steht …   Deutsch wörterbuch der biologie

  • operon — opèrōn m <G operóna> DEFINICIJA biol. jedinstvo gena operatora i strukturnih gena kojima on upravlja; pod kontrolom je fizioloških stanja u staničnoj plazmi ETIMOLOGIJA lat. operator + on …   Hrvatski jezični portal

  • operon — [äp′ə rän΄] n. [< L operare, to work (see OPERATE) + ON] a cluster of genes, with related functions acting as a coordinated unit controlled by a regulatory gene …   English World dictionary

  • Operon — A typical operon In genetics, an operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single regulatory signal or promoter.[1][2] The genes are tr …   Wikipedia

  • Operón — Un Operón se define como una unidad genética funcional formada por un grupo o complejo de genes capaces de ejercer una regulación de su propia expresión por medio de los sustratos con los que interaccionan las proteínas codificadas por sus genes …   Wikipedia Español


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