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see nucleic acidnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
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The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a special regulating protein formed in bacterial cells that halts transcription, which is the synthesis of messenger ribonucleic acid (m-RNA) from a specific operon (a group of genes that carry out the synthesis of functionally related enzymes). The number of different repressors corresponds to the number of operons.

Unlike other proteins, a repressor present in a cell consists of ten to 20 molecules. The synthesis of m-RNA ceases when a repressor combines with an operator, which is the regulating part of an operon. An effector, for example, lactose in a lactose operon, interacts with a repressor to form a complex that inactivates and produces a reversible spatial change in a repressor molecule. This type of repressor can no longer combine with an operator and, as a result, m-RNA synthesis resumes.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


An end product of metabolism which represses the synthesis of enzymes in the metabolic pathway.
The product of a regulator gene that acts to repress the transcription of another gene.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
NFKB1 gene, central mediator of the proinflammatory immune response was expressed at significantly reduced levels in PMBC of BTB-infected animals and was hypothesized as key mediator of the gene repression detected in BTB infected group (24).
Lastly, de-regulation of Polycomb complexes has been shown to be the cause of several cancers and developmental disorders emphasising the importance of understanding Polycomb-mediated gene repression in development and disease.
The molecular aspects of the occurrence of somaclonal variation have not yet been fully investigated [1], but one of the most likely factors is gene repression. There are several factors that can result in gene repression such as DNA methylation, histone methylation, and histone deacetylation.
The presence of acetochlor resulted in an attenuation of this [T.sub.3]-mediated gene repression. Finally, Table 3 lists genes that are [T.sub.3] responsive during precocious metamorphosis but not affected by acetochlor exposure.
Studies can include cloning of receptor-regulated genes, analysis of mechanisms of gene repression by nuclear receptors, evaluation of the role of receptor phosphorylation in receptor signaling, development of novel model systems to study coactivators/corepressors, and creation of tissue-specific receptor knockouts in animals.