Prokaryotic Gene Regulation and Operon Model Review

These flashcards cover key concepts of prokaryotic gene regulation, the operon model, and mechanisms of control such as positive and negative regulation.

What is an operon?

A genetic element containing an operator, promoter, and structural genes that are transcribed together.

What is the role of the promoter in an operon?

The binding site for RNA polymerase.

What does the operator do in gene regulation?

It is a DNA sequence where a repressor protein can bind to inhibit transcription.

What is the function of a repressor protein?

It binds to the operator site and inhibits transcription by preventing RNA polymerase from binding to the promoter.

What is an inducer?

A metabolite that increases gene expression by inactivating a repressor protein.

What happens when allolactose is present in the lac operon?

It inactivates the repressor, allowing transcription of the operon to occur.

What is the trp operon primarily responsible for?

Regulating tryptophan biosynthesis in response to its levels in the cell.

What occurs when tryptophan levels are high in relation to the trp operon?

The repressor binds to the operator, turning the operon OFF.

What is positive regulation in prokaryotic gene expression?

When the binding of an activator protein promotes transcription initiation.

How does cAMP affect the lac operon?

High levels of cAMP activate CAP which enhances the transcription of the lac operon.

What is feedback inhibition?

A process where the end product of a metabolic pathway inhibits an enzyme involved in its production.

When is the lac operon OFF?

When lactose is absent; an active repressor binds to the operator.

What is negative control of inducible genes?

This occurs when a repressor protein prevents transcription in the absence of an inducer.

What is the relationship between glucose levels and cAMP?

When glucose levels are low, cAMP levels are high.

When do repressible operons function?

They generally function in anabolic pathways, turning OFF when the end product is abundant.

Which operon is an example of an inducible system?

The lac operon.

Which operon is an example of a repressible system?

The trp operon.

What happens when both glucose and lactose are present for the lac operon?

The operon is typically turned OFF because glucose is preferred.

What does the term polycistronic mRNA refer to?

A single mRNA that encodes multiple proteins.

What are the two types of gene regulation discussed in prokaryotic cells?

Negative control and positive control.

What does CAP stand for in the context of the lac operon?

Catabolite Activator Protein.