341lecture13oct7sakai

341lecture13oct7sakai - Cell Biology 341 Last lecture:...

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Cell Biology 341 Weds, October 7, 2009 Today: Negative and positive regulation of procaryotic operons How do proteins bind specific DNA sequences? Bring two #2 pencils to the exam this Friday, Oct 9 Office hours this week: Thurs 2-4 pm Last lecture: The small subunit of a ribosome initiates translation by binding a consensus sequence in a procaryotic mRNA, or the 5′-cap on a eucaryotic mRNA Monocistronic versus polycistronic mRNAs Three binding sites for tRNA, the A, P and E sites, are involved in 4 steps of elongation Elongation factors use 2 GTP/peptide bond for accuracy and rearrangements Began chapter 7: Unique cell types are generated by expression of specific sets of genes A group of procaryotic genes is often arranged in an operon, with a single shared promoter
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turn off gene expression in procaryotes Repressor does not bind tryptophan, cannot bind operator Repressor binds tryptophan and binds operator (allosteric) When [tryptophan] (Trp) is high , repressor protein binds Trp. This conformation can bind to the operator DNA, blocking the binding of RNA polymerase There are five genes in the trp operon [tryptophan]
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This note was uploaded on 12/05/2009 for the course BIO 341 taught by Professor Noris during the Fall '09 term at Rhode Island.

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341lecture13oct7sakai - Cell Biology 341 Last lecture:...

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