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IUB BIOL-L 211 - Transcriptional Regulation in Prokaryotes I

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BIOL-L211 Lecture 18 Outline of Last Lecture I. ElongationII. TerminationIII. Operons Outline of Current Lecture I. Alternative Sigma FactorsII. Fla/che OperonCurrent LectureTranscriptional Regulation in Prokaryotes I*Recall from previous lecture that promoters closer to consensus will be expressed at a higher level*I. Alternative Sigma FactorsA. Mechanism of Transcription Regulation1. Transcriptional regulation uses environmental factors to adjust gene expression 2. Recall sigma factors: the proteins that determine where RNA polymerase begins transcription by seeking specific promoter sequencesB. Alternative Sigma Factors can replace σ701. σ32: heat shock sigma2. σ28: motility sigma3. σ38: starvation sigmaC. These alternative factors prefer different promotersThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.D. Coordinates gene expression regulationE. Lytic bacteriophages utilize alternative sigma factors to control expression of genes in infected cellII. ArticleA. "How Illuminating" – The Economist, May 2011B. Bioluminescence: natural emission of light by a living organism (like fireflies or jellyfish)C. Three amino acids (Tyr66, Gly67, and Ser65) undergo a chemical reaction which produces light1. Structured in a beta barrel2. Chromophore (three amino acids) at center of barrelD. Luminous proteins can be used to track various cell activityIII. fla/che OperonA. One of the longest discovered operons that controls the synthesis of flagella1. Length means that entire operon is not always transcribed2. σD is at the end of the operon, and is thus transcribed infrequentlyB. σD: alternative sigma factor in transcription of the flagellin gene1. Flagella filament composed of flagellin C. Transcriptional fusion1. Used to confirm that flagellin was not always transcribed2. Process fuses a specific promoter to a "reporter gene"a. Reporter protein can be easily detected (like a fluorescent protein)b. Gene will be transcribed3. Flagellin gene promoter is placed in front of fluorescent gene4. Reporter indicates whether or not promoter is activated for transcription5. Further experimentation showed that moving σD to the front of the operon increased frequency of promoter


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