2E PP - Trp Operon Repressor

What is gene regulation?

The process of turning gene expression (transcription & translation) on or off.

Gene Regulation Exam Definition

The cellular control of the amount (how much) and timing (when) of the functional product (protein) of a gene.

What does gene regulation control?

The amount (how much) and timing (when) of the functional product (protein) of a gene.

Why do different cells have different phenotypes despite having the same genome?

Different genes are expressed in different cells.

Structural Genes

A structural gene is a gene that codes for a protein that becomes part of the structure or function of an organism. These genes are regulated by regulatory genes.

Regulatory Gene

Regulatory genes are genes that control the expression of structural genes. They do this by coding for proteins called transcription factors.

What is the role of transcription factors?

They bind to the promoter region (TATA box) and influence RNA polymerase's affinity for binding to DNA.

What is an operon?

A group of genes under the control of a single promoter, allowing coordinated regulation.

What is the function of the trp operon?

It codes for enzymes that produce the amino acid tryptophan.

What happens when tryptophan is low?

RNA polymerase binds to the promoter and transcribes the trp operon structural genes.

What occurs when tryptophan concentration is high?

Tryptophan binds to the repressor protein, allowing it to bind to the operator and block transcription.

What is attenuation in the context of the trp operon?

A method of regulating transcription termination based on the level of tRNA-bound tryptophan.

What is the structure of the trp operon?

It includes structural genes trpE, trpD, trpC, trpB, trpA, and a regulatory gene (TrpR).

What is the role of the repressor in the trp operon?

It controls the transcription of structural genes by binding to the operator region.

What is the TATA box?

A promoter region where transcription factors bind to initiate transcription.

What happens to the repressor when tryptophan is not available?

The repressor remains inactive and does not bind to the operator.

What is the result of the repressor binding to the operator?

Transcription of the structural genes is blocked, preventing tryptophan production.

How does the concentration of tryptophan affect the repressor's shape?

Binding of tryptophan changes the conformation of the repressor, enabling it to bind to the operator.

What is the significance of the attenuator sequence?

It allows for the regulation of transcription termination in the trp operon.

What is the outcome of high levels of tRNA-bound tryptophan?

Transcription is terminated without the repressor binding to the operator.

What is the function of RNA polymerase in the trp operon?

It binds to the promoter to transcribe the operon's structural genes.

What happens to the trp operon when tryptophan levels decrease?

The repressor returns to its original shape, allowing transcription to resume.

What is the basal rate of transcription in the trp operon?

It is low due to the periodic binding and unbinding of the trp repressor to the operator.