LacOperon

LacOperon - Transcriptional Regulation Regulation of Gene...

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1 1 Transcriptional Regulation 2 Regulation of Gene Expression • Transcriptional inhibition/enhancement • mRNA degradation/stabilization • Translational inhibition/enhancement • Protein degradation/stabilization • Inhibition/stimulation of protein function 3 The Lac Operon: A Model of Transcriptional Regulation 4 Lactose Metabolism Adapted from Fig 19.2
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2 5 Jacob and Monot: β -galactosidase expression is induced by the presence of lactose in bacterial growth media 6 β -Galactosidase Induction is Affected by Mutations in Five Complementation Groups Gene: Protein/Phenotype lacZ : Encodes β -galactosidase lacY : Encodes permease (originally thought to encode transacetylase) lacI : Inhibits lacZ, Y and A expression when lactose is absent lacO : Mutations in O are similar in effect to mutations that inactivate the ability of LacI to regulate Z, Y , and A expression lacP : Required for lacY, Z, and A expression 7 LacZ ,Y, and A are Located on a Polycistronic (Polygenic) mRNA Fig 19.4 Lac operon polycistronic mRNA 8 What is an Operon? • A system of gene regulation where multiple genes are under control of a single promoter • Consists of a polycistronic mRNA and its regulatory elements • Genes in an operon typically function in a common metabolic pathway
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3 9 Polycistronic mRNAs Exhibit Polarity • A mutation in a gene encoded by a polycistronic mRNA will often block translation of downstream genes in the same RNA molecule
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LacOperon - Transcriptional Regulation Regulation of Gene...

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