BIO 3570 Study Guide - Final Guide: Trp Operon, Lac Operon, Lambda Phage
15 Jan 2017
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Control of the expression of genes in prokaryotes (1) Initiation rate: number of syntheses of molecules of mrna units initiated by unit of time. This reflects the rate of formation of the rna polymerase/promotor complex. Consensus sequences: in the region of the promotor a) the tataat sequence situated at position -10 (10 nucleotide pairs upstream from the transcription starting site); b) ttgaca sequence situated in position -35. Proteins that change the affinity of rnap for the promotor. If the proteins increase the affinity of the polymerase activator; if they decrease the affinity of the polymerase repressors. Positive control: genes under positive control will not be expressed until the presence of an activator regulating protein. There"s still base levels of expression but when there"s an activator protein, the expression increases. Negative control: genes under negative control are expressed unless a repressor protein prevents their expression.
