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 two or more genes transcribed into a single mRNA under the same regulatory control, while a regulon is a set of operons and/or genes all under control of the same regulatory protein.

Question 2

A mutation in the promoter region of a bacterial operon prevents RNA polymerase from binding. What is the most likely outcome?

Accepted Answer

Transcription of the operon will be blocked, and no mRNA will be produced.

Question 3

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

Accepted Answer

The lac operon repressed by the LacI repressor in the absence of lactose.

Question 4

In the arginine operon, what role does arginine play in regulating gene expression?

Accepted Answer

Arginine acts as a corepressor, binding to the repressor protein and blocking transcription.

Question 5

Which of the following statements about DNA-binding proteins in bacteria is correct?

Accepted Answer

DNA-binding proteins often recognize inverted repeats and bind as homodimers.

Question 6

A bacterium uses a two-component system to sense environmental phosphate levels. Which sequence of events correctly describes this process?

Accepted Answer

A sensor kinase detects phosphate, autophosphorylates, transfers the phosphate to a response regulator, which then modulates gene expression.

Question 7

Which of the following best explains how quorum sensing can increase bacterial virulence?

Accepted Answer

Quorum sensing triggers the production of virulence factors only when the bacterial population reaches a threshold density, maximizing the impact on the host.

Question 8

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

Accepted Answer

sRNAs can directly phosphorylate proteins to activate them.

Question 9

Which of the following is a key difference between hepatitis B and hepatitis C viruses?

Accepted Answer

Hepatitis B can lead to acute and chronic disease, while hepatitis C usually leads to chronic hepatitis.

Question 10

Which of the following best describes antigenic shift in influenza viruses?

Accepted Answer

A sudden reassortment of genome segments between different influenza viruses, leading to new viral strains.

Question 11

A mutation causes the maltose activator protein to lose its ability to bind maltose. What is the most likely effect on the maltose operon?

Accepted Answer

The operon will not be transcribed in the presence of maltose.

Question 12

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

Accepted Answer

Transcription machinery in Archaea is more similar to eukaryotes, but regulation is more similar to Bacteria.

Question 13

Which of the following equations best represents the positive feedback loop in quorum sensing?

Accepted Answer

$$A \rightarrow B \rightarrow C \rightarrow A$$

Question 14

Which of the following is a plausible consequence of the loss of all scientists performing advanced genetic testing for hepatitis outbreaks in the U.S.?

Accepted Answer

Delayed identification and response to multi-state hepatitis outbreaks.

Question 15

Which of the following best describes the role of a corepressor in negative transcriptional control?

Accepted Answer

A corepressor binds to a repressor protein, enabling it to bind the operator and block transcription.

Question 16

Which of the following is NOT a function of regulatory RNAs in bacteria?

Accepted Answer

Directly catalyzing the synthesis of proteins.

Question 17

Which of the following is a real-world example of positive control of gene expression?

Accepted Answer

The maltose operon activated by the maltose activator protein in the presence of maltose.

Question 18

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

Accepted Answer

Biofilm formation is only advantageous when enough cells are present to make the structure effective.

Question 19

Which of the following statements about the influenza virus genome is correct?

Accepted Answer

The influenza genome is segmented, allowing for reassortment and antigenic shift.

Genetic Regulation and Viral Pathogenesis in Microbiology

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