Definitions for lac operon
lac oper·on

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1. Lac operon

   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 bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of beta-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.Bacterial operons are polycistronic transcripts that are able to produce multiple proteins from one mRNA transcript. In this case, when lactose is required as a sugar source for the bacterium, the three genes of the lac operon can be expressed and their subsequent proteins translated: lacZ, lacY, and lacA. The gene product of lacZ is β-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose. lacY encodes Beta-galactoside permease, a membrane protein which becomes embedded in the cytoplasmic membrane to enable the cellular transport of lactose into the cell. Finally, lacA encodes β-galactoside transacetylase. It would be wasteful to produce enzymes when no lactose is available or if a preferable energy source such as glucose were available. The lac operon uses a two-part control mechanism to ensure that the cell expends energy producing the enzymes encoded by the lac operon only when necessary. In the absence of lactose, the lac repressor, lacI, halts production of the enzymes encoded by the lac operon. The lac repressor is always expressed, unless a co-inducer binds to it. In other words, it is transcribed only in the presence of small co-inducer molecules. In the presence of glucose, the catabolite activator protein (CAP), required for production of the enzymes, remains inactive, and EIIAGlc shuts down lactose permease to prevent transport of lactose into the cell. This dual control mechanism causes the sequential utilization of glucose and lactose in two distinct growth phases, known as diauxie.

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1. lac operon

   The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria. It consists of three adjacent structural genes, lacZ, lacY, and lacA. The genes encode β-galactosidase, lactose permease, and thiogalactoside transacetylase, respectively. In its natural environment, the lac operon allows for the effective digestion of lactose. The lactose permease, which sits in the cytoplasmic membrane, transports lactose into the cell. β-galactosidase, a cytoplasmic enzyme, subsequently cleaves lactose into glucose and galactose. However, it would be wasteful to produce the enzymes when there is no lactose available or if there is a more preferable energy source available, such as glucose. Gene regulation of the lac operon was the first genetic regulatory mechanism to be understood clearly and is one of the foremost examples of prokaryotic gene regulation. The lac operon is one of the most basic methods for explanation of how a repressor enzyme works within a cell on DNA and for that reason is discussed in many introductory molecular and cellular biology classes at universities. The lac operon uses a two-part control mechanism to ensure that the cell expends energy producing the enzymes encoded by the lac operon only when necessary. It achieves this primarily with the lac repressor, which halts the production in the absence of lactose, and EIIAGlc, which shuts down lactose permease when glucose is being transported into the cell. This dual control mechanism causes the sequential utilization of glucose and lactose in two distinct growth phases, known as diauxie.

U.S. National Library of MedicineRate this definition:0.0 / 0 votes

1. Lac Operon

   The genetic unit consisting of three structural genes, an operator and a regulatory gene. The regulatory gene controls the synthesis of the three structural genes: BETA-GALACTOSIDASE and beta-galactoside permease (involved with the metabolism of lactose), and beta-thiogalactoside acetyltransferase.

How to pronounce lac operon?

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Numerology

1. Chaldean Numerology

   The numerical value of lac operon in Chaldean Numerology is: 5

2. Pythagorean Numerology

   The numerical value of lac operon in Pythagorean Numerology is: 9

References

1. ^ Wikipedia
   https://en.wikipedia.org/wiki/Lac_Operon
2. ^ Wikidata
   https://www.wikidata.org/w/index.php?search=lac operon