Question 1

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

Accepted Answer

A group of genes transcribed into a single mRNA, all under the same regulatory control.

Question 2

In the arginine operon, which molecule acts as a corepressor to block transcription?

Accepted Answer

Arginine

Question 3

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

Accepted Answer

Positive control uses activator proteins to enhance RNA polymerase binding, while negative control uses repressors to block RNA polymerase.

Question 4

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

Accepted Answer

Specificity of DNA-binding proteins is provided by interactions between amino acid side chains and chemical groups on DNA bases.

Question 5

A bacterial cell is exposed to a sudden increase in lactose. Which regulatory mechanism is most likely to be activated?

Accepted Answer

Enzyme induction of the lac operon

Question 6

Which equation best represents the relationship between mRNA degradation rate ($$k_{deg}) $$and steady-state mRNA concentration ($$[mRNA]_{ss}) if $$synthesis rate is $$k_{syn}$$?

Accepted Answer

$$[mRNA]_{ss} = k_{syn} / k_{deg}$$

Question 7

Which of the following is true about two-component regulatory systems in bacteria?

Accepted Answer

They consist of a sensor kinase and a response regulator.

Question 8

Quorum sensing in bacteria is best described as:

Accepted Answer

A mechanism for bacteria to regulate gene expression in response to cell density via signaling molecules.

Question 9

Which of the following is a real-world example of a behavior regulated by quorum sensing?

Accepted Answer

Biofilm formation on medical devices

Question 10

Which hepatitis virus requires co-infection with another hepatitis virus to replicate?

Accepted Answer

Hepatitis D virus

Question 11

Which of the following mechanisms can regulatory RNAs use to modulate gene expression?

Accepted Answer

Base pairing with target mRNA to block or expose ribosome binding sites

Question 12

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

Accepted Answer

An operon is a group of genes transcribed together, while a regulon is a set of operons and/or genes under control of the same regulatory protein.

Question 13

Which of the following is a plausible consequence of a mutation that disrupts the inverted repeat sequence in a bacterial promoter?

Accepted Answer

Decreased specificity of DNA-binding protein interactions

Question 14

Influenza virus can alter its genome by two processes. Which process involves the exchange of gene segments between different viral strains?

Accepted Answer

Antigenic shift

Question 15

Which of the following is a correct statement about gene regulation in Archaea?

Accepted Answer

Regulation of transcription in Archaea is more similar to Bacteria than to Eukaryotes.

Question 16

A mutation in the maltose activator protein prevents it from binding to the activator-binding site. What is the most likely outcome?

Accepted Answer

Transcription of the maltose operon is blocked.

Question 17

Which of the following best explains why some bacterial behaviors are only advantageous at high cell densities?

Accepted Answer

Quorum sensing ensures that energy-intensive processes like biofilm formation occur only when enough cells are present.

Question 18

Which of the following is a direct effect of small regulatory RNAs (sRNAs) binding to mRNA in bacteria?

Accepted Answer

They alter the secondary structure of mRNA, affecting translation initiation.

Question 19

Which of the following is a plausible outcome if a bacterial cell loses the ability to degrade mRNA efficiently?

Accepted Answer

Increased steady-state mRNA concentration

Genetic Regulation and Viral Pathogenesis in Microbiology

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