Question 1

Which of the following best describes transcriptional control in bacterial gene expression?

Accepted Answer

It determines whether mRNA is synthesized from DNA, thus controlling which proteins can be made.

Question 2

A bacterial cell is exposed to a sudden increase in a toxic compound. Which level of gene regulation would allow the cell to respond most rapidly to this environmental change?

Accepted Answer

Post-translational control

Question 3

Which of the following is an example of a gene that is likely to be expressed constitutively in bacteria?

Accepted Answer

A gene coding for an enzyme involved in glycolysis

Question 4

Which of the following statements about negative control of transcription is correct?

Accepted Answer

A repressor protein binds to DNA and prevents RNA polymerase from initiating transcription.

Question 5

In the context of global gene regulation, what is a regulon?

Accepted Answer

A set of separate genes or operons controlled by the same regulatory protein and regulatory sequences.

Question 6

Which of the following mechanisms allows for the most rapid change in protein activity in response to environmental signals?

Accepted Answer

Post-translational control

Question 7

A mutation in the gene encoding the LexA protein in E. coli results in a nonfunctional LexA repressor. What is the most likely consequence for the SOS regulon?

Accepted Answer

The SOS genes will be constitutively expressed, regardless of DNA damage.

Question 8

Which of the following best explains why transcriptional control is considered more energy efficient than post-translational control?

Accepted Answer

It prevents the synthesis of unnecessary mRNA and proteins, conserving resources.

Question 9

Which scenario best illustrates translational control of gene expression in bacteria?

Accepted Answer

A small RNA molecule binds to an mRNA, causing it to be degraded before it can be translated.

Question 10

A researcher discovers a bacterial gene that is only expressed when a specific sugar is present in the environment. Which regulatory mechanism is most likely responsible for this gene's expression?

Accepted Answer

Negative control by a repressor protein that is inactivated by the sugar

Question 11

Which of the following equations best represents the flow of genetic information in a bacterial cell?

Accepted Answer

$$DNA \rightarrow RNA \rightarrow Protein$$

Question 12

If a mutation causes a bacterial cell to produce a repressor protein that cannot bind to DNA, what is the most likely effect on the gene it regulates?

Accepted Answer

The gene will be transcribed continuously, regardless of environmental signals.

Question 13

Which of the following is NOT a mechanism by which translational control can occur in bacteria?

Accepted Answer

Regulatory proteins affecting RNA polymerase binding to the promoter

Question 14

A bacterial cell needs to quickly turn off a DNA repair system after the DNA damage has been fixed. Which regulatory mechanism is most likely involved?

Accepted Answer

Transcriptional control by repressors such as LexA

Question 15

Which of the following best describes the difference between negative and positive control of transcription?

Accepted Answer

Negative control involves a repressor protein that shuts down transcription, while positive control involves an activator protein that triggers transcription.

Question 16

Which of the following is a real-world example of post-translational control in bacteria?

Accepted Answer

A protein is phosphorylated to become active in response to a stress signal.

Control of Gene Expression in Bacteria

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