Genetics: From Genes to Genomes

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