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OUTLINE 3 Control of Gene Expression in Prokaryotes A. Regulatory proteins B. The operon model C. Examples 1. t

OUTLINE 3 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. 18.21. Negative regulation:

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OUTLINE 3 Control of Gene Expression in Prokaryotes A. Regulatory proteins B. The operon model C. Examples 1. t

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  1. OUTLINE 3 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)

  2. Fig. 18.21 Negative regulation: Substrate induction

  3. Fig. 18.22a Positive regulation of the lac operon

  4. Fig. 18.22b Positive regulation of the lac operon

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

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

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

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

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

  10. Negative regulation: end-product repression Fig 18.20

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