GeneRegulation160-page3 - the controller molecule binds to...

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Gene Regulation - 3 Regulatory Gene A regulatory gene codes for a repressor protein. The regulatory gene is located on the DNA some distance apart from the rest of the operon. Repressors typically work with controller molecules, which typically are substances in the cell. A repressor can be active when attached to its controller molecule or deactivated when attached to a controller molecule. In an inducible operon, the gene is normally "off". The repressor actively blocks the gene from transcription. When the controller molecule attaches to the repressor, it removes the repressor from the operator and transcription proceeds. In a repressible operon the gene is normally "on" and the gene is being transcribed. The repressor does not blocking gene transcription unless
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Unformatted text preview: the controller molecule binds to the repressor. When that happens, the repressor, with its controller attached, actively blocks transcription. Inducible Operon Repressible Operon We will look at two prokaryotic operons: the lactose operon, an inducible operon and the tryptophan operon, a repressible operon. The Lactose Operon – An Inducible Operon To get an idea of how genes get regulated, we will look at the Lactose operon, described by Jacob and Monod in E. coli . The lactose operon contains the three genes that code for the enzymes that degrade lactose. In the absence of lactose, the controller substance, the repressor inhibits transcription by blocking RNA polymerase from attaching to the promoter....
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This note was uploaded on 12/29/2011 for the course BIO 151 taught by Professor Edwards during the Spring '10 term at SUNY Stony Brook.

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