Question 1

Which of the following best describes the difference between an operon and a regulon in bacterial gene regulation?

Accepted Answer

An operon is a group of genes transcribed together from a single promoter, while a regulon is a set of genes or operons controlled by the same regulatory protein, possibly at different locations in the genome.

Question 2

In the context of negative control of transcription, what is the role of a corepressor?

Accepted Answer

It binds to a repressor protein, enabling the repressor to bind to the operator and block transcription.

Question 3

A mutation in the -10 region of a bacterial promoter is most likely to affect which process?

Accepted Answer

Binding of RNA polymerase and initiation of transcription

Question 4

Which of the following scenarios best illustrates positive control of gene expression?

Accepted Answer

An activator protein binds upstream of the promoter, recruiting RNA polymerase and increasing transcription when an inducer is present.

Question 5

Which of the following is a direct result of quorum sensing in bacteria?

Accepted Answer

Activation of genes involved in biofilm formation when cell density is high

Question 6

A bacterial cell has a mutation that prevents the production of small regulatory RNAs (sRNAs). Which of the following processes would be most directly affected?

Accepted Answer

Post-transcriptional regulation of gene expression by base-pairing with mRNAs

Question 7

Which of the following best explains how a riboswitch can regulate gene expression?

Accepted Answer

A metabolite binds directly to the mRNA, causing a conformational change that affects transcription or translation.

Question 8

In the arginine operon, what happens when arginine is abundant in the cell?

Accepted Answer

Arginine acts as a corepressor, enabling the repressor to bind the operator and block transcription.

Question 9

Which of the following is a key feature of two-component regulatory systems in bacteria?

Accepted Answer

A sensor kinase detects an environmental signal and phosphorylates a response regulator, which then modulates gene expression.

Question 10

Which of the following statements about the lac operon is correct?

Accepted Answer

The lac operon is induced when lactose is present, as lactose (allolactose) binds to the repressor, preventing it from blocking transcription.

Question 11

A mutation causes the activator-binding site of the maltose operon to be deleted. What is the most likely outcome?

Accepted Answer

Transcription of the maltose operon will not occur, even in the presence of maltose.

Question 12

Which of the following mechanisms is NOT a way that small regulatory RNAs (sRNAs) can modulate gene expression?

Accepted Answer

Directly phosphorylating RNA polymerase

Question 13

Which of the following best describes the process of feedback inhibition?

Accepted Answer

The end product of a metabolic pathway inhibits the activity of an enzyme involved earlier in the pathway.

Question 14

Which of the following is a likely consequence of antigenic shift in the influenza virus genome?

Accepted Answer

A major change in viral surface proteins, potentially leading to pandemics due to lack of population immunity.

Question 15

Which of the following is true regarding the regulation of gene expression in Archaea?

Accepted Answer

The machinery for transcription is more similar to eukaryotes, but the regulation of transcription is more similar to bacteria.

Question 16

Which of the following best explains why some bacterial behaviors, such as biofilm formation, are regulated by quorum sensing?

Accepted Answer

These behaviors are only advantageous when the population density is high.

Question 17

Which of the following is a correct statement about the role of inverted repeats in DNA?

Accepted Answer

They often serve as binding sites for homodimeric DNA-binding proteins involved in gene regulation.

Question 18

A patient is diagnosed with hepatitis B virus (HBV) infection. Which of the following statements is correct regarding HBV?

Accepted Answer

HBV can cause acute, often severe disease that may lead to liver failure and death.

Question 19

Which of the following best describes the function of the sensor kinase in a two-component regulatory system?

Accepted Answer

It detects an environmental signal and autophosphorylates a histidine residue using ATP.

Genetic Regulation in Microbial Systems: Operons, Regulons, and Control Mechanisms

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