Question 1

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

Accepted Answer

Multiple genes controlled by a single promoter and transcribed together as one mRNA.

Question 2

What is the function of the Shine-Dalgarno sequence in prokaryotic gene expression?

Accepted Answer

It helps the ribosome bind to mRNA for translation initiation.

Question 3

Which of the following is NOT a way a cell can produce different amounts of protein from the same gene?

Accepted Answer

Changing the DNA sequence of the gene

Question 4

In a two-component regulatory system in bacteria, what is the role of the sensor kinase?

Accepted Answer

It senses environmental signals and phosphorylates itself.

Question 5

Which equation best represents the rate of mRNA degradation if $$k is $$the degradation constant and $$[mRNA] is $$the concentration?

Accepted Answer

$$\frac{d[mRNA]}{dt} = -k \cdot [mRNA]$$

Question 6

A bacterium is exposed to a new environmental signal. Which gene type would most likely begin synthesizing mRNA only under these conditions?

Accepted Answer

Inducible gene

Question 7

During quorum sensing, what triggers the sensor kinase to activate the response regulator?

Accepted Answer

High concentration of signaling molecules released by bacteria

Question 8

Which of the following best describes cassette switching in gene regulation?

Accepted Answer

A process where a silent gene replaces a previously expressed gene without the need for a new promoter.

Question 9

If a cell wants to quickly reduce the amount of a specific protein, which regulatory mechanism would be most effective?

Accepted Answer

Decrease mRNA half-life

Question 10

Which of the following is TRUE about prokaryotic gene expression?

Accepted Answer

Prokaryotes can start protein synthesis at internal sites of mRNA due to operons.

Question 11

A gene is described as 'constitutive.' What does this mean?

Accepted Answer

It synthesizes mRNA constantly, regardless of environmental changes.

Question 12

Which regulatory protein in a two-component system directly alters gene expression in response to environmental signals?

Accepted Answer

Response regulator

Question 13

If a gene is 'turned off,' what is happening at the molecular level?

Accepted Answer

The gene is not being expressed and no protein is being made.

Question 14

Which of the following scenarios best illustrates the application of regulating translation to control protein levels?

Accepted Answer

A cell increases the number of ribosomes binding to mRNA, resulting in more protein production.

Question 15

Which process allows bacteria to sense and respond to population density?

Accepted Answer

Quorum sensing

Question 16

A repressive gene is most likely to:

Accepted Answer

Stop synthesizing mRNA under certain conditions.

Question 17

Which of the following is a plausible consequence of a mutation in the Shine-Dalgarno sequence of an operon?

Accepted Answer

Ribosomes may fail to bind to mRNA, reducing protein synthesis.

Question 18

Which regulatory mechanism would be most effective for a cell to rapidly increase protein production in response to a sudden environmental change?

Accepted Answer

Activate inducible genes to start synthesizing mRNA.

Question 19

If a cell regulates the half-life of its mRNA, which equation describes the relationship between mRNA concentration and time, assuming first-order decay?

Accepted Answer

$$[mRNA](t) = [mRNA]_0 \cdot e$$^{-kt}$$

Question 20

Which of the following is a direct result of regulating protein degradation in a cell?

Accepted Answer

The amount of protein present in the cell can be decreased independently of mRNA levels.

Regulation of Gene Expression in Bacteria

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