Lac Operon HB 24/25

Describe the process of transcription initiation in the lac operon.

• Transcription initiation occurs when RNA polymerase binds to the promoter after the repressor is removed by the inducer, allowing the genes to be transcribed.

• Transcription initiation occurs when RNA polymerase binds to the operator, preventing transcription of the genes.

• Transcription initiation occurs when the repressor binds to the promoter, blocking RNA polymerase from attaching.

• Transcription initiation occurs when the inducer binds to the operator, allowing RNA polymerase to transcribe the genes.

Explain the concept of negative regulation in the lac operon.

• Negative regulation occurs when a repressor protein binds to the operator to prevent transcription, effectively turning off gene expression.

• Negative regulation enhances gene expression by promoting transcription.

• Negative regulation involves the activation of the promoter region to increase transcription.

• Negative regulation is the process of removing repressor proteins to allow gene expression.

What is the difference between an inducer and a corepressor?

• An inducer activates gene expression by inhibiting the repressor, while a corepressor enhances the repressor's ability to inhibit transcription.

• An inducer enhances the repressor's ability to inhibit transcription, while a corepressor activates gene expression by inhibiting the repressor.

• An inducer and a corepressor both activate gene expression in the same way.

• An inducer inhibits transcription, while a corepressor activates gene expression.

What is the function of the inducer in the lac operon?

• The inducer binds to the repressor, causing it to change shape and release from the operator, allowing RNA polymerase to transcribe the genes necessary for lactose metabolism.

• The inducer activates the repressor, preventing transcription of the genes necessary for lactose metabolism.

• The inducer binds to RNA polymerase, enhancing its ability to transcribe all genes in the operon.

• The inducer degrades the repressor, permanently stopping its function in the operon.

How does the binding of the repressor to the operator affect gene expression?

• It enhances the transcription of the genes.

• It allows RNA polymerase to transcribe the genes freely.

• It blocks RNA polymerase from transcribing the genes, thus preventing gene expression.

• It has no effect on gene expression.

What role does the repressor play in the lac operon?

• The repressor enhances the transcription of the genes when lactose is present.

• The repressor binds to the operator region of the lac operon, blocking RNA polymerase from transcribing the genes when lactose is not present.

• The repressor promotes the binding of RNA polymerase to the promoter region.

• The repressor is involved in the degradation of lactose in the cell.

What is the relationship between glucose levels and the lac operon activity?

• When glucose levels are high, the lac operon is repressed, as bacteria prefer glucose over lactose for energy.

• When glucose levels are low, the lac operon is repressed, as bacteria prefer lactose over glucose for energy.

• Glucose levels have no effect on the lac operon activity; it is always active.

• The lac operon is activated when glucose levels are high, allowing for lactose metabolism.

What is the significance of the lac operon in bacteria?

• It allows bacteria to efficiently utilize lactose as an energy source when glucose is not available.

• It regulates the synthesis of amino acids in bacteria.

• It helps bacteria to resist antibiotics.

• It is involved in the replication of bacterial DNA.

What is the promoter in the lac operon?

• The region of DNA where RNA polymerase binds to initiate transcription of the lac operon genes.

• A protein that enhances the binding of RNA polymerase to the DNA.

• A sequence that terminates transcription of the lac operon genes.

• A region that prevents the expression of the lac operon genes.

What happens when lactose is present in the environment of a bacterial cell?

• Lactose inhibits the transcription of the lac operon genes.

• Lactose acts as an inducer, binding to the repressor and allowing transcription of the lac operon genes to occur.

• Lactose is converted into glucose and galactose without affecting the lac operon.

• Lactose has no effect on the bacterial cell's gene expression.