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

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. 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.

eron/movie-flash.htm hill.com/sites/ /student_view0/cha pter12/animation_quiz_3.html mations/content/lacoperon.html hill.com/olc/dl/120080/bio27.swf Operon.mov