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Lecture 18

Lecture 18 - Gene Expression - BIOL308.pdf
Lecture 18 - Gene Expression - BIOL308.pdf

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University of Waterloo
BIOL 308
Bruce Wolff

Lecture 18Remember in prokaryotes gene regulation allows a single cell to adjust to its environmentGenes encoding catabolic enzymes are off when not needed and only turned on when the substrate is presentProkaryotic genes are organized into operons also transcription and translation are coupledRapid response to changes in environment by rapd change in gene expressionExample after sensing lactose in their environment bacteria make 50000 copies of needed enzymes in 90 secondsGene expression in bacteria some useful terminologydistinctions similar in EuConstitutive genesContinuously expressed required for on going survival of the cell housekeeping genes Ie Those required for protein synthesis glucose metabolismutilization etcRegulated inducible genesExpression is regulated induced or suppressed as needed depending on the changes in environmentBacterial genes organized into operonsStructural genesRegulatory sequences binding sites for regulatory proteinsRegulatory genes regulatory proteins separateWhy do we have to learn about lac operon againBecause it shows basic concepts of regulation of gene expression at transcription initiation level in both Pro and EuThe facts we are going to learn from lac and other operonsKey regulators of transcription are sequencespecific DNA binding proteins1ProteinDNA or proteinproteinDNA interactions can either repress or activatetranscription2There is more then one regulatory proteininvolved in regulation of expression of a particular gene or an 3operon specific recruitment and involvement would depend on conditionsSome small moleculescan play key roles in gene expression by binding to regulatory proteinsand 4changing their conformationTwo types of transcription regulationInhibit transcription negative regulation1Regulatory proteins in active state turn off the expressionBinding siteoperator NOTES FROM LECTURES Page 1
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