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Copyright 2009 Pearson Education, Inc. Chapter 17 Regulation of Gene Expression in Prokaryotes Copyright 2009 Pearson Education, Inc. Slide 2 Constitutive enzymes Adaptive enzymes Inducible Repressible Regulation, whether inducible or repressible, can be: Negative Positive Prokaryotes Respond to Environmental Conditions Slide 3 Copyright 2009 Pearson Education, Inc. Genes that code for related enzymes tend to be clustered together Under control of a single regulatory region Regulatory region is cis and located upstream The genes and the regulatory region are called an operon Operon Slide 4 Copyright 2009 Pearson Education, Inc. The Lac Operon - Inducible The Trp Operon - Repressible The Ara Operon positive and negative control Common Operons in Prokaryotes Slide 5 Copyright 2009 Pearson Education, Inc. Figure 17.1 The Lac Operon Slide 6 Copyright 2009 Pearson Education, Inc. Figure 17.2 Slide 7 Copyright 2009 Pearson Education, Inc. Figure 17.3 Slide 8 Copyright 2009 Pearson Education, Inc. Using a gratuitous inducer IPTG Isopropylthiogalactoside Constitutive mutants How was the operon discovered? Slide 9 Copyright 2009 Pearson Education, Inc. Figure 17.4 IPTG Slide 10 Copyright 2009 Pearson Education, Inc. Figure 17.5a Slide 11 Copyright 2009 Pearson Education, Inc. Figure 17.5b Slide 12 Copyright 2009 Pearson Education, Inc. Figure 17.5c Slide 13 Copyright 2009 Pearson Education, Inc. Figure 17.6 Two Constitutive Mutants Slide 14 Copyright 2009 Pearson Education, Inc. Figure 17.8 CAP Catabolite Activating Protein Slide 15 Copyright 2009 Pearson Education, Inc. Figure 17.9 cAMP Slide 16 Copyright 2009 Pearson Education, Inc. Figure 17.12a The Trp Operon Slide 17 Copyright 2009 Pearson Education, Inc. Figure 17.12b Slide 18 Copyright 2009 Pearson Education, Inc. Figure 17.12c Slide 19 Copyright 2009 Pearson Education, Inc. A type of repression where transcription is greatly reduced, but not necessarily entirely In the Trp Operon, a leader sequence is transcribed The mRNA can form one of two hairpins Terminator hairpin when tryptophan is present Antiterminator hairpin when tryptophan is absent Attenuation Slide 20 Copyright 2009 Pearson Education, Inc. Figure 17.13ab Slide 21 Copyright 2009 Pearson Education, Inc. Figure 17.13c Slide 22 Copyright 2009 Pearson Education, Inc. Figure 17.13d Slide 23 Copyright 2009 Pearson Education, Inc. Figure 17.15 The Ara Operon