Question 1

Which of the following best describes the mechanism of negative control in bacterial gene regulation?

Accepted Answer

A regulatory protein binds to the operator and blocks RNA polymerase, preventing transcription.

Question 2

In the lac operon of E. coli, which two conditions must be met for maximal transcription of the lac genes?

Accepted Answer

High cAMP levels and presence of lactose

Question 3

A mutation in the gene encoding the sensor kinase of a two-component regulatory system would most likely result in which of the following?

Accepted Answer

The cell would be unable to detect and respond to specific environmental changes.

Question 4

Which of the following statements about riboswitches is correct?

Accepted Answer

Riboswitches are RNA elements that bind small metabolites and regulate gene expression at the level of transcription or translation.

Question 5

During chemotaxis in E. coli, what is the role of methyl-accepting chemotaxis proteins (MCPs)?

Accepted Answer

They sense attractants or repellents and transmit signals to the CheA sensor kinase.

Question 6

Which of the following best explains the phenomenon of diauxic growth observed in E. coli when both glucose and lactose are present?

Accepted Answer

E. coli first consumes glucose, then after a lag phase, switches to lactose metabolism.

Question 7

What is the function of the alarmone $$ppGpp in $$the stringent response of bacteria?

Accepted Answer

It downregulates rRNA synthesis and upregulates stress response genes during nutrient limitation.

Question 8

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

Accepted Answer

It involves the production and detection of autoinducers to coordinate group behaviors.

Question 9

A bacterium is exposed to high osmotic pressure. Which regulatory system is most likely to be involved in adjusting the expression of porin proteins such as OmpC and OmpF?

Accepted Answer

Two-component regulatory system

Question 10

Which of the following best describes the mechanism of attenuation in the trp operon of E. coli?

Accepted Answer

A leader peptide sequence causes premature termination of transcription depending on tryptophan availability.

Question 11

Which of the following is an example of post-translational regulation in bacteria?

Accepted Answer

Methylation of MCPs during chemotaxis adaptation

Question 12

In feedback inhibition, how does the end product of a biosynthetic pathway typically inhibit the pathway?

Accepted Answer

By binding to an allosteric site on the first enzyme, changing its conformation and reducing its activity

Question 13

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

Accepted Answer

sRNAs regulate gene expression by base-pairing with target mRNAs, affecting their stability or translation.

Question 14

A mutation that prevents the binding of cAMP to CRP in E. coli would most likely result in which phenotype?

Accepted Answer

Inability to activate transcription of the lac operon when glucose is absent

Question 15

Which of the following is a real-world example of quorum sensing regulating virulence in a human pathogen?

Accepted Answer

Staphylococcus aureus uses autoinducing peptides to coordinate the production of toxins.

Question 16

Which of the following best explains why attenuation does not occur in eukaryotes?

Accepted Answer

Transcription and translation are separated in eukaryotes, preventing coupling required for attenuation.

Question 17

Which of the following is a function of the RpoS sigma factor in E. coli?

Accepted Answer

It controls the general stress response, including genes for nutrient limitation and oxidative stress.

Question 18

Which of the following best describes the role of Hfq in bacterial gene regulation?

Accepted Answer

It is an RNA chaperone that facilitates the interaction between sRNAs and their target mRNAs.

Question 19

Which of the following is a likely consequence of a complete absence of (p)ppGpp in a bacterial cell?

Accepted Answer

Multiple amino acid requirements, poor survival of aged cultures, and aberrant cell division

Microbial Regulatory Systems: Mechanisms of Gene and Protein Regulation in Microorganisms

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