Biology And Biomedical Sciences BIOL 2960 Lecture 23: RNA elongation termination and the lac operon
29 Mar 2017
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Document Summary
Subunit binds to -10, -35 consensus sequences. Rna pol holoenzyme core and subunit. Promoter of different classes of genes are recognized by alternative subunits. Genes expressed only if alternative proteins are expressed in the cell. 1st nt is placed without a 3" oh still has 3 phosphates. Termination sequence g-c rich region followed by string of a"s in 3" utr. After transcription through 3"utr rna forms hairpin loop. Triggers release of a completed transcript and rna pol: rho dependent mechanism. Rho protein binds to rut site in 3" end of the rna. Acts as a helicase to disrupt the rna-dna hybrid. Regulation of transcription initiation: basal level the absence of both an activator and a repressor dna pol, only binds occasionally to the promoter. Repressor binding to the operator, blocks rna pol binding. High levels of expression: coli lac operon is regulated using a + and regulator. Allosteric effectors (inducers) bind to regulatory proteins, influencing dna binding.
