Module 14: Gene Expression and Operons

A set of 20 question-and-answer practice flashcards covering gene expression control, the trp operon, and the lac operon based on Module 14 lecture notes.

Why do cells need to control gene expression?

To make proteins only when needed, thereby conserving energy and resources.

Which organism's gene regulation systems are studied in Module 14?

Escherichia coli (E. coli).

Which structural genes comprise the trp operon in E. coli?

trpE, trpD, trpC, trpB, and trpA.

What regulatory regions precede the structural genes in the trp operon?

The promoter and the operator.

What is the function of the proteins encoded by the trp operon?

They are enzymes used to synthesize tryptophan.

When tryptophan is present in the environment, is the trp repressor activated or inactivated?

Activated.

Where does the trp repressor bind when it is activated?

To the operator region.

Will the trp operon make its designated proteins when tryptophan is present in the environment? Why or why not?

No, because tryptophan activates the repressor, which binds the operator and blocks transcription.

What type of operon system is the trp operon classified as?

A repressible operon system.

Which structural genes comprise the lac operon in E. coli?

lacZ, lacY, and lacA.

What is the function of the proteins encoded by the lac operon?

They help with the transport and breakdown of lactose.

When lactose is present in the environment, is the lac repressor activated or inactivated?

Inactivated.

Will the lac operon make its designated proteins when lactose is present in the environment? Why or why not?

Yes, because lactose inactivates the repressor, allowing transcription of the lac genes.

How much transcription of lac genes occurs when both lactose and glucose are present?

Some transcription occurs.

How much transcription of lac genes occurs when lactose is present but no glucose is present?

A lot of transcription occurs.

How much transcription of lac genes occurs when glucose is present but no lactose is present?

Not at all (no transcription occurs).

What type of operon system is the lac operon classified as?

An inducible operon system.

What is the main function of the promoter region in bacterial operons?

It serves as the binding site for RNA polymerase to initiate transcription.

What is the role of the operator in gene expression within an operon?

It is the DNA segment where a active repressor protein binds to inhibit RNA polymerase transcription.

What happens to the lac operon when lactose is completely absent from the cell's environment?

The lac repressor remains active and bound to the operator, preventing transcription of the lac genes.