HO-16 - BIO 320 lecture 16 Reading: Chapter 17 Problems:...

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lactose permease (lacY) allolactose β -galactosidase (lacZ) glucose + galactose Different sigma proteins help RNA polymerase to recognize different promoters and express different sets of genes, depending on the bacterial cell's need to cope with a changing environment σ 70 normal (-35)TTGACA (-10) TATAAT σ 32 heat shock, stress (-39)CCCCC (-16) TATAAATA σ 54 low nitrogen levels (-26)GTGGC (-14) TTGCA sigma growth conditions promoter elements 1. Sigma proteins as transcriptional regulators BIO 320 Reading: Chapter 17 lecture 16 Problems: Question bank B Text 17.1, 5, 7, 8, 10, 12, 14, 17 Regulating gene expression in bacteria: the operon model Most cells contain a complete set of genes, but most genes are not expressed at the same level all the time. Gene expression is regulated in response to many different changes inside and outside the cell. Examples: nutrient availability the cell division cycle changing time of day various types of stress cell differentiation sensory experience; learning Mechanisms for gene regulation were first worked out in the bacterium E. coli. Coliform bacteria normally live in your gut - a niche where the type and amount of available nutrients can change rapidly. Their preferred carbon source is glucose, but they can respond to the appearance of a different nutrient by switching on genes encoding enzymes to metabolize it. Several different "switches" are used. 2. Coordinated gene regulation: inducible transcription in the lac operon of E. coli
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This note was uploaded on 06/03/2008 for the course BIO 320 taught by Professor N/a during the Spring '08 term at SUNY Stony Brook.

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HO-16 - BIO 320 lecture 16 Reading: Chapter 17 Problems:...

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