Lecture 15 BILD1 SP10

Lecture 15 BILD1 SP10 - Announcements NOTICE! SECTION A03...

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1 Announcements NOTICE! SECTION A03 with TA Jonathon Chang Cancelled this week, Tues. May 25th, 5-5:50 PM No Class, Sections, OHs on Mon. May 31st see website for make-up TA hours (Fri. May 28th-Wed. June 2nd) Final Exam Preparation EXTRA OFFICE HOURS next week (see website) REVIEW SESSION Wed. June 9, 6:00-8:00 PM, Ledden Auditorium 216 Please ±ll in your online CAPE evaluations Figure 17.25 TRANSCRIPTION DNA RNA polymerase transcript RNA PROCESSING Exon Poly-A pre-mRNA Intron NUCLEUS Cap INITIATION COMPLEX CYTOPLASM mRNA Growing polypeptide Ribosomal subunits Aminoacyl-tRNA synthetase Amino acid tRNA AMINO ACID ACTIVATION Activated amino acid TRANSLATION Anticodon A CC AAA UGGUUUAUG U AC E A Ribosome 5 5 3 Codon A gene is a region of DNA whose ±nal product is either a polypeptide or an RNA molecule Lecture 15 Regulation of Gene Expression Bacteria regulate their gene expression in response to environment E. coli , a bacteria that lives in human colon – Can tune its metabolism to the changing environment and food sources
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2 Metabolic control on two levels Feedback Inhibition Adjust activity of metabolic enzymes already present Figure 18.2 Enzyme 1 Enzyme 2 Enzyme 3 Enzyme 4 Enzyme 5 Tryptophan Precursor Gene 2 Gene 1 Gene 3 Gene 4 Gene 5 Gene Expression Regulate transcription of genes encoding metabolic enzymes DNA proteins Protein Protein levels Operons: The Basic Concept Bacterial genes are often clustered into regulated operons Operons contain: 1. Operator , an “on-off” switch - turned OFF by repressor 2. Promoter , to initiate transcription 3. Cluster of genes for metabolic enzymes that act at different steps in same pathway Repressible and Inducible Operons: Two Types of Negative Gene Regulation • In a repressible operon – Binding of a speci±c repressor protein to the operator shuts off constitutive transcription • In an inducible operon – Binding of an inducer to an innately active repressor inactivates the repressor and turns on transcription Repressible and Inducible Operons: Two Types of Negative Gene Regulation • In a repressible operon – Binding of a speci±c repressor protein to the operator shuts off constitutive transcription • In an inducible operon – Binding of an inducer to an innately active repressor inactivates the repressor and turns on transcription
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3 The trp repressible operon: regulated synthesis of repressible enzymes Figure 18.3 Genes of operon Inactive repressor Protein Operator Polypeptides that make up enzymes for tryptophan (Trp) synthesis Promoter RNA pol Promoter operon 5’ 3’ mRNA 5’ trpD trpE trpC trpB trpA trpR DNA mRNA E D C B A IF Tryptophan absent, THEN repressor inactive, operon ON Need Trp Synthesis Enzymes!
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Lecture 15 BILD1 SP10 - Announcements NOTICE! SECTION A03...

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