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CHAPTER 14 GENE REGULATION IN BACTERIA AND BACTERIOPHAGES



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PowerPoint Presentation Materials to accompany Genetics Analysis and Principles Robert J Brooker CHAPTER 14 GENE REGULATION IN BACTERIA AND BACTERIOPHAGES Copyright The McGraw Hill Companies Inc Permission required for reproduction or display INTRODUCTION The term gene regulation means that the level of gene expression can vary under different conditions Genes that are unregulated are termed constitutive They have essentially constant levels of expression Frequently constitutive genes encode proteins that are necessary for the survival of the organism The benefit of regulating genes is that encoded proteins will be produced only when required Copyright The McGraw Hill Companies Inc Permission required for reproduction or display 14 2 INTRODUCTION Gene regulation is important for cellular processes such as 1 Metabolism 2 Response to environmental stress 3 Cell division Regulation can occur at any of the points on the pathway to gene expression Refer to Figure 14 1 Copyright The McGraw Hill Companies Inc Permission required for reproduction or display 14 3 Figure 14 1 14 4 14 1 TRANSCRIPTIONAL REGULATION The most common way to regulate gene expression in bacteria is at the transcriptional level The rate of RNA synthesis can be increased or decreased Transcriptional regulation involves the actions of two main types of regulatory proteins Repressors Bind to DNA and inhibit transcription Activators Bind to DNA and increase transcription Negative control refers to transcriptional regulation by repressor proteins Positive control to regulation by activator proteins Copyright The McGraw Hill Companies Inc Permission required for reproduction or display 14 5 Small effector molecules affect transcription regulation However these bind to regulatory proteins and not to DNA directly In some cases the presence of a small effector molecule may increase transcription These molecules are termed inducers They function in two ways Bind activators and cause them to bind to DNA Bind



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