chapter 18 weinstein

chapter 18 weinstein - Chapter 18 Regulation of Gene...

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1 Chapter 18 Regulation of Gene Expression • Regulation of Bacterial operons • Regulation of Eukaryotic gene expression • Development gene regulation • Gene expression related to Cancer Fig. 18.2 REGULATION OF GENE EXPRESSION IN BACTERIA Definitions structural gene - gene that codes for a protein trpE trpE trpE gene trpE mRNA trpE protein operon - linked structural genes related functions (e.g. biochem. pathway) single promoter controls transcription single messenger RNA is produced that encodes multiple proteins (polycistronic) -allows coordinated regulation of pathway 18.3 operator - transcriptional regulatory sequence located between promoter and structural genes binding site for a regulatory protein ( repressor ) Promoter operator structural gene repressor operator - transcriptional regulatory sequence located between promoter and structural genes binding site for a regulatory protein ( repressor ) if repressor is bound , transcription is off if repressor is not bound , transcription occurs example of negative control of gene expression Promoter operator structural gene Promoter operator structural gene mRNA repressor
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2 repressor is always produced, at low level repressor gene is not linked to operon allosteric protein controlled by key metabolites 18.3 Tryptophan (trp) operon when trp is absent : cells must express operon to survive trp repressor is inactive when trp is present : expression of operon is unnecessary save energy – turn if off trp binds to repressor, activates it Fig. 18.3 - Trp operon Trp absent, repressor inactive, operon on Trp present, repressor active, operon off Lac operon under negative and positive control Logic behind control circuit: Lactose isn’t made by the cell, its taken up from outside If there is none in the environment, there is no need to make the stuff to get it Lac operon under negative and positive control Logic behind control circuit: when lactose is absent : expression of operon is unnecessary
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This note was uploaded on 11/29/2010 for the course BIO 113 taught by Professor Swenson during the Fall '08 term at Ohio State.

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chapter 18 weinstein - Chapter 18 Regulation of Gene...

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