308 Lecture 17

308 Lecture 17 - Transcription: Prokaryotes E. coli RNA...

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1 Transcription: Prokaryotes Learning Objectives Define levels of control of gene expression Define transcriptional machinery Discuss the organization of bacterial genes Describe the process of promoter recognition by E. coli RNAP including the role of specific subunits and the cis -elements that are involved Explain the factors that affect the strength of a promoter E. coli RNA polymerase
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2 Gene expression Process in which information carried by a gene is converted into observable product Transcription First step in gene expression - process where one strand of a DNA molecule is used as a template for synthesis of a complementary RNA, mRNA, which carries information for a specific protein = RNA like =coding =sense
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3 1cell system (Bacteria): Has to survive and reproduce Gene expression regulation - to adjust to changes in its nutritional environment - to enable cell growth and cell division Multi-cellular organism: Has to survive and reproduce but also to grow and develop; different parts of the body – different function Gene expression regulation during: Development (time) Tissue differentiation (space and “space/time combo”) Stress (as a response to environmental stress- induction) Gene expression and changes in gene expression are controlled - regulated
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4 Prokaryotes: transcription initiation is controlled transcription and translation occur in the same compartment Regulation of Gene Expression: Pro mRNA is polycistronic, without introns and has short half-life
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5 Regulation of Gene Expression: Eu Gene expression can be regulated at various levels in Eukaryotes In Eu, transcription initiation is most important level of regulation as well
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6 Transcription (general) Similar process to DNA synthesis Enzyme – multisubunit complex Enzyme produces nucleotide strand in 5’ to 3’ direction Mg 2+ is a co-factor (necessary to add to buffers for in vitro transcription) Both DNA strands could be templates for RNA synthesis
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7 genes a, d, e genes b, c, f, g
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8 However, there are some important differences : Enzyme is RNA polymerase (RNAP) RNAP does not require a primer Promoter sequences (binding sites for RNAP) are
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308 Lecture 17 - Transcription: Prokaryotes E. coli RNA...

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