Question 1

Which of the following best describes the function of a transcription activator in gene regulation?

Accepted Answer

It recruits RNA polymerase to the promoter and may remodel chromatin to increase gene transcription.

Question 2

A bacterial cell is exposed to a sudden increase in temperature. Which sigma factor is most likely to be activated, and what is its primary function?

Accepted Answer

$$\$$sigma^{32}$$; it activates heat-shock genes to help the cell cope with stress.

Question 3

Which of the following mechanisms is used by transcription repressors to inhibit gene expression?

Accepted Answer

Competitive binding to the promoter or operator, blocking RNA polymerase.

Question 4

In the context of chromatin remodeling, what is the effect of histone acetyltransferases (HATs) on gene expression?

Accepted Answer

They add acetyl groups to histones, resulting in open chromatin and increased transcription.

Question 5

A riboswitch in the 5′ untranslated region of an mRNA binds a metabolite. What is the most likely outcome?

Accepted Answer

The mRNA changes shape, which can block translation or cause premature transcription termination.

Question 6

Which of the following best explains the 'rheostat' effect in gene regulation?

Accepted Answer

Gene expression levels are adjusted gradually by the combined action of multiple activators and repressors.

Question 7

What is the primary role of anti-sigma factors in bacterial gene regulation?

Accepted Answer

They bind to sigma factors, preventing them from associating with RNA polymerase until needed.

Question 8

Which of the following scenarios best illustrates the function of an anti-anti-sigma factor?

Accepted Answer

A protein binds to an anti-sigma factor, releasing the sigma factor to activate transcription in response to stress.

Question 9

Which of the following is a correct statement about microRNAs (miRNAs) in eukaryotic gene regulation?

Accepted Answer

miRNAs bind to complementary mRNA sequences, leading to mRNA degradation or inhibition of translation.

Question 10

A mutation prevents the production of long non-coding RNAs (lncRNAs) in a mammalian cell. Which of the following processes is most likely to be disrupted?

Accepted Answer

Chromatin remodeling and X-chromosome inactivation.

Question 11

Which of the following best describes the function of antisense RNA in gene regulation?

Accepted Answer

It binds to mRNA, forming double-stranded RNA that blocks translation or triggers mRNA degradation.

Question 12

How do CRISPR-Cas systems provide adaptive immunity in bacteria?

Accepted Answer

By using crRNAs to guide Cas enzymes to matching viral DNA, which is then cut and destroyed.

Question 13

Which of the following is a key feature of second messengers in cellular signaling?

Accepted Answer

They amplify and distribute signals from cell-surface receptors to multiple targets inside the cell.

Question 14

A cell uses a transcription–translation negative feedback loop (TTFL) to regulate a protein involved in circadian rhythms. Which of the following best describes this process?

Accepted Answer

The protein accumulates and eventually inhibits its own gene's expression, creating a cycle.

Question 15

Which of the following is an example of a molecular thermometer in bacteria?

Accepted Answer

An RNA thermometer in the 5′ UTR that unfolds at high temperature, allowing translation of heat-shock proteins.

Question 16

Which of the following best describes a molecular switch in cellular regulation?

Accepted Answer

A mechanism that allows a cell to flip between two stable states, often using positive feedback or phosphorylation.

Question 17

A researcher introduces a mutation that prevents the removal of acetyl groups from histones in a eukaryotic cell. What is the most likely effect on gene expression?

Accepted Answer

Gene expression will increase due to more open chromatin.

Question 18

Which of the following statements about RNA interference (RNAi) is correct?

Accepted Answer

miRNAs and siRNAs both guide the cell to silence specific mRNAs, but siRNAs often originate from external sources like viruses.

Question 19

A bacterial cell is exposed to nutrient starvation. Which sigma factor is most likely to be involved in the response, and what is its function?

Accepted Answer

$$\$$sigma^{38}$$; activates genes for survival during starvation or stationary phase.

Question 20

Which of the following is a real-life application of antisense RNA technology?

Accepted Answer

Silencing disease-causing genes by introducing complementary antisense RNA to block translation.

Molecular Regulation in Microbiology: Mechanisms and Applications

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