Question 1

Which of the following best explains why bacteria regulate protein production at the transcriptional level?

Accepted Answer

To conserve energy and respond to environmental changes

Question 2

In the context of bacterial transcriptional regulation, what is the primary function of a repressor protein?

Accepted Answer

It binds to the operator region and blocks RNA polymerase, reducing transcription

Question 3

Which of the following equations correctly represents the total energy cost (in ATP and GTP) for synthesizing a polypeptide of $$n$$ amino acids in bacteria?

Accepted Answer

$$n$$ ATP + $$1$$ GTP + $$3n$$ GTP + $$1$$ GTP = $$n$$ ATP + $$(3n+2)$$ GTP

Question 4

A mutation in the operator region of the lac operon prevents the repressor from binding. What is the most likely outcome?

Accepted Answer

Transcription of the lac operon will be constitutively active

Question 5

Which of the following best describes the role of sigma factors in bacterial transcription?

Accepted Answer

They direct RNA polymerase to specific promoter sequences

Question 6

In a two-component signal transduction system, what is the correct sequence of events following detection of an environmental signal?

Accepted Answer

Sensor kinase autophosphorylates, transfers phosphate to response regulator, which then binds DNA to regulate transcription

Question 7

Which of the following is a key feature of quorum sensing in Gram-negative bacteria?

Accepted Answer

Use of acyl-homoserine lactone (AHL) as an autoinducer

Question 8

A bacterial population produces light only at high cell density. Which regulatory mechanism is most likely responsible for this phenomenon?

Accepted Answer

Quorum sensing

Question 9

Which of the following statements about small regulatory RNAs (sRNAs) in bacteria is TRUE?

Accepted Answer

sRNAs function primarily by base-pairing with mRNAs to regulate translation and stability

Question 10

Which of the following mechanisms can sRNAs use to increase translation of a target mRNA?

Accepted Answer

Binding upstream of the RBS to open up the RBS for ribosome binding

Question 11

A bacterium is exposed to a sudden increase in environmental copper, which is toxic. Which regulatory system is most likely to be activated to confer resistance?

Accepted Answer

Two-component signal transduction system

Question 12

Which of the following best defines a regulon?

Accepted Answer

A collection of genes and operons controlled by a single regulatory protein

Question 13

If a mutation prevents the phosphorylation of the response regulator in a two-component system, what is the most likely consequence?

Accepted Answer

The response regulator will not bind DNA, and target gene expression will not be regulated in response to the signal

Question 14

Which of the following is an example of positive control of transcription in bacteria?

Accepted Answer

An activator protein binding to DNA and increasing RNA polymerase recruitment

Question 15

In the maltose regulon, what is the role of maltose as an effector molecule?

Accepted Answer

It binds to the maltose activator protein, allowing it to promote transcription of maltose utilization genes

Question 16

Which of the following scenarios best illustrates the function of an sRNA that stabilizes mRNA?

Accepted Answer

An sRNA binds to the mRNA and blocks ribonuclease activity, resulting in increased translation

Question 17

Which of the following is a direct consequence of quorum sensing in pathogenic bacteria at high cell density?

Accepted Answer

Induction of virulence traits to overwhelm host defenses

Question 18

Which of the following best describes the difference between an operon and a regulon?

Accepted Answer

An operon is a group of genes transcribed together from a single promoter, while a regulon is a collection of genes and operons controlled by a single regulatory protein

Question 19

A researcher discovers a new bacterial gene that is only expressed when a specific small RNA is present. Which mechanism is most likely responsible for this regulation?

Accepted Answer

The sRNA binds upstream of the RBS, exposing the RBS and enhancing translation

Question 20

Which of the following is NOT a typical mechanism by which sRNAs regulate gene expression in bacteria?

Accepted Answer

Directly phosphorylating response regulators

Transcriptional Regulation in Bacteria: Mechanisms and Examples

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