MICRO CH10and12

MICRO CH10and12 - +October 5, 2010 Selected topics from...

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+October 5, 2010 Selected topics from chapter 10 and 12 Chapter 10- Molecular Regulation Regulating Gene Expression Microbes respond to changing environment Alter growth rate Alter proteins produced Must sense their environment Receptors on cell surface Must transmit information to chromosome Alter gene expression Change transcription rate Change translation rate Sensing the Environment Two- component signal transduction 1 Sensor kinase protein in CM Binds to signal Food Chemical cue Activates itself via phosphorylation 2. Cytoplasmic response regulator Takes phosphate from sensor Binds chromosome Alters transcription rate of multiple genes
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Altering Transcription Rates Sigma (σ) factor guides RNA polymerase to initiate transcription at promoter Proteins can help guide sigma factor to promoter Acitvator binds to DNA sites next to promoter Increases frequency of that gene’s transcription Proteins can block sigma factor from binding Repressor Binds to DNA sites next to promoter o Operator Lowers frequency of that gene’s transcription The amount of an enzyme in the cell can be controlled by decreasing (repression) or increasing (induction) the amount of mRNA that encodes the enzyme For negative control of transcription the regulatory molecule is called a Repressor protein and it functions by inhibiting mRNA synthesis The E. coli lac Operon Lactose (milk sugar) is used as nutrient source Cannot pass through cell membrane Lactose permease allows entry Disaccharide lactose must be cleaved into monosaccharides to be digested Beta-galactosidaes cleaves lactose People also make b-galactosidase If not, person is lactose-intolerant The lacZ encodes b-galactosidase
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The lacY encodes lactose permease Need both proteins to digest lactose
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This note was uploaded on 02/23/2012 for the course BIOL 2051 taught by Professor Brininstool during the Fall '07 term at LSU.

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MICRO CH10and12 - +October 5, 2010 Selected topics from...

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