Genetics: From Genes to Genomes

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The utilization of lactose by E. coli:A model system for gene regulation• The presence of lactose induces expression of the genesrequired for lactose utilization• Induction – stimulation of protein synthesis• Inducer – molecule that stimulates synthesis• Lactose – inducer of genes for lactose utilization• 1950s and 1960s – Golden era of bacterial genetics• Advantages of E. coli and lactose utilization system• Culture large numbers of bacteria allow isolation of rare mutants• Lactose genes not essential for survival (can use glucose as carbonsource)• Induction increases expression 1000-fold making mutant identificationeasy• Color changes using β-galactosidaseenzyme (e.g., OPNG, X-gal) Xmakemeasurement of expression levels efficient.Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display17-8
Coordinate repression and induction of three genesrevealed by studies of lactose-utilization mutants• Jacques Monod and Francois Jacob –Pasteur Institute in Paris• Proposed Operon Theory of gene regulation• Single signal can simultaneously regulate expressionof several genes that are clustered together on achromosome and involve the same process.• Because genes are clustered, they are transcribedtogether as single mRNA.• Clusters of genes are called Operons.Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display17-9
Page 1 and 2: Powerpoint to accompanyGenetics: Fr
Page 3: Outline of Chapter 17• There are
Page 6 and 7: Fig. 17.2Copyright © The McGraw-Hi
Page 10 and 11: The Operon Theory• The players•
Page 12 and 13: The Operon Theory• Induction• L
Page 14 and 15: Experimental evidence for repressor
Page 16 and 17: Inducer releases repressor to trigg
Page 18 and 19: Changes in the operator can alsoaff
Page 20 and 21: Three experiments elucidate cis and
Page 22 and 23: ConstitutiveInsert Figure 17.9chere
Page 24 and 25: Some positive regulators increasetr
Page 26 and 27: Many DNA-Binding proteins containa
Page 28: Most regulatory proteins are oligom
Page 31 and 32: Using the lacZ gene as a reporter o
Page 33 and 34: Creating acollection oflacZinsertio
Page 35 and 36: The attenuation of gene expression:
Page 37 and 38: Termination of transcription finetu
Page 39 and 40: Global regulatory mechanisms coordi
Page 41 and 42: What enables transcription of σ 32
Page 43 and 44: Microarrays - a tool for uncovering
Page 45 and 46: Regulation of Virulence Genes inV.
Page 47 and 48: • Isolated a gene that regulates
Page 49: Unanswered Questions Remain• Why

Genetics: From Genes to Genomes

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