Class lec ol 15-16 Gene reg

Class lec ol 15-16 Gene reg - GENE REGULATION Review of...

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GENE REGULATION Review of Gene Regulation Ref. Brock - figure - Regulation of enzyme synthesis is most important - Can make mRNA but not translate it - Less regulated is where you make the enzyme but you regulate its activity, if it is needed then it is available right away - Housekeeping genes not regulated (glucose breakdown genes, phosphofructokinase) Gene Regulation occurs at many levels - including Cell cycle Fig 6.2 o Not really controlling at the transcriptional level o E. coli Req’s 40 min to replicate its DNA and 20 min after termination of replication to prepare for division
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Slow growing =60 min Fast Growing cell cycle completed in 20 minutes 40 minutes for DNA replication 20 minutes for septum formation and cytokinesis look at timing-how can this happen? Second, third or fourth round of replication can begin before first round of replication is completed DNA replication Role of Ori C and DnaA - Ori C o Sequestering of hemimethylated OriC o GATC sited (in OriC not fully methylated) o Needs to be fully methylated for initiation to start - DnaA o Levels increase with respect to OriC but takes some time o Ensures DNA replication will not start prematurally Enzyme activity - Allosteric regulation - Covalent modification - Feed back inhibition o E.g. Phosphofructokinase (“key” enzyme in glycolysis) o Inhibited by ATP and citrate o Stimulated by ADP Levels of Regulation of Gene Expression - transcription initiation - transcription elongation - translation - posttranslation
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prokaryotes:
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eukaryotes:
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Three domains of life differ in genome structure and regulatory mechanisms used Regulation of Transcription Initiation induction and repression of enzyme synthesis constitutive genes always synthesized as housekeeping genes that are always expressed inducible genes β -Galactosidase an inducible enzyme that functions in a catabolic pathway reaction catalyzed is lactose hydrolysis into galactose and glucose level of enzyme rises (~3 vs. 3,000 molecules) in presence of inducer, a small effector molecule - adding lactose increases its expression - until lactose is added it is not active, but when lactose is added the activity greater increases - catabolic pathways mostly inducible - with a.a. biosynthetic pathways, if you add the a.a. then the expression goes down Induction and Repression of Enzyme levels-ref Brock - lactose enters the cell by lactose permease and then aldolactose causes gene expression of lac operon Control of Transcription Initiation by Regulatory Proteins Their activity is modulated by inducers, corepressors and inhibitors induction and repression occur because of the activity of regulatory proteins these proteins either inhibit transcription (negative control) or promote transcription (positive control) their activity is modulated by inducers, corepressors and inhibitors their end products are the corepressors for negative control Negative Control - animation regulatory protein (repressor) – found in two forms the active form that is
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Class lec ol 15-16 Gene reg - GENE REGULATION Review of...

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