Gene expression- lac operon
- Created by: Saf54
- Created on: 13-02-19 12:18
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- Gene expression
- Regulating gene expression
- Enzymes that catalyse metabolic reactions in basic cellular functions
- Synthesised at constant rates
- Enzymes that are only needed under specific conditions
- Synthesised at varying rates according to the needs of the cell
- Enzymes that catalyse metabolic reactions in basic cellular functions
- The lac operon
- E.coli metabolises glucose as respiratory substrate
- If glucose is absent and lactose is present
- Lactose induces the production of 2 enzymes
- Lactose permease- allows lactose to enter bacterial cell
- B galactosidase-hydrolyses lactose into glucose+galactose
- It’s the lactose not the absence of glucose that induces enzymes
- Lactose induces the production of 2 enzymes
- If glucose is absent and lactose is present
- E.coli metabolises glucose as respiratory substrate
- What is the lac operon?
- Length of DNA , 6000 base pairs long
- Contains an operator region, lacO,that’s next to the structural genes
- LacZ codes for enzyme B galactosidase
- LacY codes for lactose permease
- Next to operator region (lacO) is the promoter region P
- The enzyme RNA polymerase binds to begin transcription of lacZ and lacY
- Length of DNA , 6000 base pairs long
- how the lac operon works
- Next to operon is repressor gene I that codes for repressor protein lacI
- When regulatory gene is expressed, repressor protein binds to operator
- Preventing RNA polymerase from binding to the promoter region
- Repressor protein prevents genes lacZ&lacY from being expressed
- Enzymes for lactose metabolism aren’t made
- Repressor protein prevents genes lacZ&lacY from being expressed
- Preventing RNA polymerase from binding to the promoter region
- When regulatory gene is expressed, repressor protein binds to operator
- Switching genes off
- Switching genes on
- Repressor protein binds to operator preventing transcription
- Stops RNA polymerase from binding to the promoter region
- Lactose binds to repressor protein
- Repressor protein leaves the operator
- RNA polymerase can bind and transcribe the genes
- Produces B galactosidase & lactose permease
- RNA polymerase can bind and transcribe the genes
- Repressor protein leaves the operator
- Lactose binds to repressor protein
- Stops RNA polymerase from binding to the promoter region
- Repressor protein binds to operator preventing transcription
- Next to operon is repressor gene I that codes for repressor protein lacI
- Regulating gene expression
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