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The lac Operon in E. coli
Concept 10: The Effect of Glucose and Lactose on the lac Operon
   Practice (1 page)
Concept 10: The Effect of Glucose and Lactose on the lac Operon
When both glucose and lactose are present, the genes for lactose metabolism are transcribed to a small extent.
Maximal transcription of the lac operon occurs only when glucose is absent and lactose is present. The action of cyclic AMP and a catabolite activator protein produce this effect.