OUTLINE 3 III.Control of Gene Expression in Prokaryotes A. Regulatory proteins B. The operon model C. Examples 1. the lac operon (substrate induction)

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Presentation transcript:

OUTLINE 3 III.Control of Gene Expression in Prokaryotes A. Regulatory proteins B. The operon model C. Examples 1. the lac operon (substrate induction) 2. the tryp operon (end product repression) 3. the lac operon (positive control)

Fig Negative regulation: Substrate induction

Fig a Positive regulation of the lac operon

Fig b Positive regulation of the lac operon

Lac Operon No food Glucose? Lactose? Low: cAMP high, CRP attaches Low: Repressor attached Operon is ready to be enhanced but is shut off

Lac Operon Milk Glucose? Lactose? Low: cAMP high, CRP attaches High: Repressor removed Operon is on and enhanced

Lac Operon Milkshake Glucose? Lactose? High: cAMP low, CRP off Low: Repressor removed Operon is on but un-enhanced

Lac Operon Powerade Glucose? Lactose? High: cAMP low, CRP off Low: Repressor attached Operon is off and un-enhanced

Lac Operon No food: ready to be enhanced but off Milk: enhanced transcription Milkshake: un-enhanced transcription Powerade: off and un-enhanced

Fig Negative regulation: end-product repression