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Genetics of Viruses and Bacteria . Ch 18. Operon – consists of the operator, the promoter, and the genes Operator – “switch” controls transcription …repressor binding site Repressor – binds to operator and controls transcription by blocking the attachment of RNA Polymerase to the promoter.
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Operon – consists of the operator, the promoter, and the genes Operator – “switch” controls transcription …repressor binding site Repressor – binds to operator and controls transcription by blocking the attachment of RNA Polymerase to the promoter
Corepressor – cooperates w/ repressor to switch the operon off. (*tryptophan controls the regulation of the gene by binding to the repressor when tryptophan is present….p338 Fig 18.19) Repressible enzymes – anabolic…build or synthesize end products from raw materials *Make end product if needed and suspend production if already present. *Tryptophan is a repressible operon usually on but can be repressed/inhibited when tryptophan binds to the repressor. http://highered.mcgraw-hill.com/olc/dl/120080/bio26.swf
Inducible enzymes- catabolic….break down into simpler molecules, inactivates the repressor. *lactose is an inducible operon….usually off but when stimulated/induced lactose binds to the repressor and mRNA is transcribed *present only when substrate is present.
http://vcell.ndsu.nodak.edu/animations/lacOperon/movie-flash.htmhttp://vcell.ndsu.nodak.edu/animations/lacOperon/movie-flash.htm http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter12/animation_quiz_3.html http://www.sumanasinc.com/webcontent/animations/content/lacoperon.html http://highered.mcgraw-hill.com/olc/dl/120080/bio27.swf http://phsgirard.org/APbiology/Chapter18/LacOperon.mov