Question 1

Which of the following best describes an operon in bacterial gene regulation?

Accepted Answer

A set of genes transcribed into a single mRNA under the control of one promoter.

Question 2

In the lac operon, what is the role of allolactose?

Accepted Answer

It acts as an inducer, binding to the repressor and preventing it from binding to the operator.

Question 3

Which of the following is TRUE regarding two-component regulatory systems in bacteria?

Accepted Answer

They consist of a sensor kinase and a response regulator.

Question 4

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

Accepted Answer

Transcription of the operon will be constitutive, regardless of arginine levels.

Question 5

Which of the following best explains why quorum sensing is advantageous for bacteria?

Accepted Answer

It enables coordinated behaviors, such as biofilm formation, that are only beneficial at high cell densities.

Question 6

Which of the following statements about regulatory RNAs (sRNAs) is CORRECT?

Accepted Answer

sRNAs can either block or expose the ribosome binding site on mRNA, affecting translation.

Question 7

Which of the following is a key difference between positive and negative transcriptional control?

Accepted Answer

Positive control involves activator proteins that enhance transcription, while negative control involves repressor proteins that inhibit transcription.

Question 8

A bacterium is exposed to a sudden increase in maltose. Which regulatory mechanism is most likely to be activated?

Accepted Answer

Positive control by an activator protein that requires maltose as an inducer.

Question 9

Which of the following best describes a regulon?

Accepted Answer

A set of operons and/or genes all under control of the same regulatory protein.

Question 10

Which of the following is a mechanism by which riboswitches regulate gene expression?

Accepted Answer

By altering the secondary structure of mRNA in response to small molecule binding, affecting translation or transcription.

Question 11

Which of the following is a characteristic of bacterial and archaeal gene organization compared to eukaryotes?

Accepted Answer

They often organize genes into operons, lacking introns.

Question 12

A patient is diagnosed with hepatitis D. Which of the following must also be present for hepatitis D virus to replicate?

Accepted Answer

Hepatitis B virus

Question 13

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

Accepted Answer

Reassortment of genome segments between different influenza viruses, leading to new combinations.

Question 14

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

Accepted Answer

Activation of virulence factor genes at high cell density.

Question 15

Which of the following is TRUE about the interaction of DNA-binding proteins with DNA?

Accepted Answer

They often bind to specific sequences, such as inverted repeats, in the major groove of DNA.

Question 16

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 17

Which of the following best describes the function of a corepressor in gene regulation?

Accepted Answer

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

Question 18

Which hepatitis virus is most commonly associated with chronic infection and progression to liver cirrhosis in the United States?

Accepted Answer

Hepatitis C virus

Question 19

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

Accepted Answer

They use a sensor kinase to detect environmental signals and a response regulator to mediate cellular response.

Question 20

Which of the following mechanisms can regulatory sRNAs use to increase gene expression?

Accepted Answer

Decreasing the degradation of target mRNA by ribonucleases.

Genetic Regulation and Viral Pathogenesis in Microbiology

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