Question 1

Which of the following best describes the regulation of the lac operon when glucose is limiting and lactose is present?

Accepted Answer

Both positive and negative control: cAMP-CRP acts as an activator (positive control) and allolactose removes the lac repressor (negative control).

Question 2

In the lac operon, what is the function of the gene product coded by lacZ?

Accepted Answer

It converts lactose into allolactose and breaks lactose into glucose and galactose.

Question 3

Which of the following statements about Trimble 1 in Pyrococcus is correct?

Accepted Answer

Trimble 1 can act as both a repressor and an activator protein, depending on its binding site and the presence of maltose.

Question 4

What is the effect of maltose binding to Trimble 1 in Pyrococcus?

Accepted Answer

It removes Trimble 1 from both maltose utilization and glucose synthesis genes, allowing maltose utilization and stopping glucose synthesis.

Question 5

Which of the following best describes the role of NRPR in nitrogen metabolism in archaea?

Accepted Answer

NRPR acts as a repressor protein, blocking transcription factor binding to the promoter when ammonia is present.

Question 6

In a two-component regulatory system, which sequence of events occurs after the sensor kinase detects an environmental signal?

Accepted Answer

The sensor kinase autophosphorylates, then transfers the phosphate to the response regulator, which regulates transcription.

Question 7

Which formula correctly represents the phosphorylation reaction catalyzed by a sensor kinase using ATP?

Accepted Answer

Sensor kinase + ATP $$\rightarrow$$ Sensor kinase-P + ADP

Question 8

In E. coli, what happens to nitrogen assimilation gene transcription when ammonia is abundant?

Accepted Answer

NR1 response regulator is not phosphorylated, so transcription of nitrogen assimilation genes is repressed.

Question 9

Which of the following best explains how E. coli adjusts the ratio of OMPF and OMPC porins in response to osmotic pressure?

Accepted Answer

The sensor kinase detects osmotic pressure, phosphorylates OMR, which acts as a repressor for OMPF in high osmolarity and an activator for OMPC.

Question 10

Which of the following is a real-world application of the two-component system in bacterial motility?

Accepted Answer

Sensor kinase and response regulator control flagellar rotation, allowing bacteria to run or tumble in response to attractants or repellents.

Question 11

Quorum sensing in bacteria is best described as:

Accepted Answer

A group behavior regulated by detection of signaling molecules, activating virulence factor production when cell density is high.

Question 12

Which molecule is commonly used in bacterial quorum sensing to signal cell density?

Accepted Answer

AI3 (autoinducer 3)

Question 13

What is the primary purpose of the stringent response in bacteria?

Accepted Answer

To pause transcription and translation, activate amino acid biosynthesis, and promote survival during amino acid limitation.

Question 14

Which molecule acts as an alarmone during the stringent response, and what is its general formula?

Accepted Answer

ppGpp, with the formula $$	ext{Guanosine}-(	ext{tetra/penta})	ext{phosphate}$$

Question 15

Which of the following is NOT a consequence of the stringent response?

Accepted Answer

Increased translation of all proteins

Question 16

Which of the following is an example of horizontal gene transfer in bacteria?

Accepted Answer

Transformation: uptake of free DNA from the environment by a competent cell

Question 17

During transformation, what is required for a bacterial cell to take up free DNA from the environment?

Accepted Answer

The cell must be competent, either naturally or induced by chemical or electrical methods.

Question 18

Which process involves a virus accidentally packaging host DNA and transferring it to another bacterial cell?

Accepted Answer

Transduction

Question 19

Which of the following best describes the difference between vertical and horizontal gene transfer?

Accepted Answer

Vertical gene transfer is from parent to offspring; horizontal gene transfer is between cells of the same generation.

Microbial Regulatory Systems and Horizontal Gene Transfer

Study Guide - Practice Questions