1.1 Regulation of Transcription of the Lactose Operon

What ensures that genes are active only when required in protein synthesis?

Control mechanisms that regulate gene activity.

What are the types of regulatory mechanisms in bacteria, archaea, and eukaryotes?

Antisense RNAs, micro RNAs, and riboswitches.

What are operons?

Coordinated sets of genes regulated as a single unit, found only in bacteria and archaea.

What is the difference between inducible and repressible operons?

Inducible are activated by substrates; repressible are turned off by products.

What is a catabolic operon?

An operon that is induced by the substrate of the enzymes it codes for.

What is a repressible operon?

An operon that is turned off by the product synthesized by the enzyme.

What is the Lactose Operon?

A model for inducible gene regulation in bacteria.

What feature in the lac operon codes for a protein that can repress the operon?

The regulator.

What does the promoter in the control locus do?

It is recognized by RNA polymerase.

What is the function of the operator in the control locus?

It acts as an on/off switch.

What is the structural locus in the lac operon composed of?

Three genes coding for enzymes needed to catabolize lactose.

How is the lac operon best described in terms of genetic control?

It is the best understood system for explaining genetic induction.

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

To inhibit the expression of the operon when lactose is absent.

When is the lac operon activated?

When lactose is present in the environment.

What are the three features of the lac operon?

Regulator, control locus, and structural locus.

What is the relationship between an inducer and an operon?

An inducer activates the transcription of genes in an operon.

What is the main function of riboswitches?

To regulate gene expression through changes in RNA structure.

What are micro RNAs involved in?

They are involved in the regulation of gene expression post-transcriptionally.

In what organisms are operons primarily found?

Bacteria and archaea.

What role do antisense RNAs play in gene regulation?

They inhibit the translation of specific mRNAs.

What happens to repressible operons when their end product is abundant?

They are turned off to prevent overproduction.

How do catabolic operons respond to the presence of substrates?

They are induced to produce the necessary enzymes.

What is the primary function of the structural genes in the lac operon?

To code for enzymes that catabolize lactose.

What occurs during the induction of the lac operon?

Lactose binds to the repressor, allowing transcription to occur.

What is the significance of the operon model in genetics?

It illustrates how multiple genes can be regulated together.

What does gene regulation allow cells to do?

It allows cells to respond to environmental changes effectively.

What type of control do repressible operons exhibit?

Negative control, where gene expression is turned off.

What triggers the activation of inducible operons?

The presence of specific substrates.

How does lactose indirectly affect the synthesis of enzymes in the lac operon?

By inhibiting the repressor.

What are enzymes produced only as needed an example of?

Regulatory control in protein synthesis.

What is the effect of the product of anabolic operons on gene expression?

It suppresses the operon.

How does the control locus function in terms of operons?

It determines when genes in the operon are expressed.

What does §antisé RNA do at the molecular level?

It binds to mRNA to prevent its translation.

Why is the lac operon significant as a model system?

It provides insights into gene expression regulation in prokaryotes.

What happens to the lac operon in the absence of glucose?

Lactose is metabolized, activating the operon.

What is a key characteristic of regulatory genes?

They control the activity of other genes.

What best describes the state of the lac operon when lactose is unavailable?

It remains repressed.

What switch determines whether the lac operon is on or off?

The operator.

What is the main regulatory protein in the lac operon model?

The repressor protein.

What is a common example of a catabolic operon?

The lac operon.

How can environmental factors influence the expression of operons?

By triggering the binding of inducers or repressors.

Why is understanding protein synthesis regulation important?

It enhances our understanding of cellular function and adaptation.

What is the role of RNA polymerase in gene expression?

It transcribes DNA into RNA.

What is a primary mechanism by which micro RNAs function?

They bind to mRNAs, affecting their stability or translation.

How does an inducer affect the repressor in the lac operon?

It prevents the repressor from binding to the operator.

What can happen if regulation of protein synthesis fails?

It may lead to diseases or dysfunctions.

What is the main component that allows the lactose operon to function?

The presence of lactose as a substrate.

Where are the genes for enzymes that catabolize lactose located?

In the structural locus of the lac operon.