Question 1

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

Accepted Answer

Two or more genes transcribed into a single mRNA under the control of one promoter region.

Question 2

What is the main function of DNA-binding proteins in transcriptional regulation?

Accepted Answer

To bind to the major groove of DNA and regulate transcription by interacting with specific nucleotide sequences.

Question 3

In the context of the lac operon, what is the role of the inducer allolactose?

Accepted Answer

It binds to the repressor, causing it to release from the operator and allowing transcription to proceed.

Question 4

Which of the following is an example of negative control of gene expression?

Accepted Answer

The arginine operon repressed by the ArgR repressor in the presence of arginine.

Question 5

How do two-component regulatory systems typically function in bacteria?

Accepted Answer

By using a sensor kinase to detect environmental signals and a response regulator to alter gene expression.

Question 6

Which of the following statements about quorum sensing is correct?

Accepted Answer

Quorum sensing involves the accumulation of signaling molecules that regulate gene expression in response to cell density.

Question 7

Which mechanism allows small RNAs (sRNAs) to regulate gene expression in bacteria?

Accepted Answer

By base pairing with target mRNAs to alter their translation or stability.

Question 8

What is the main difference between an operon and a regulon?

Accepted Answer

An operon is a group of genes transcribed together, while a regulon is a set of operons and/or genes all under control of the same regulatory protein.

Question 9

Which of the following best describes the effect of a corepressor in negative control of gene expression?

Accepted Answer

It binds to the repressor protein, enabling it to bind to the operator and block transcription.

Question 10

A mutation in the promoter region of a bacterial operon prevents RNA polymerase binding. What is the most likely outcome?

Accepted Answer

Transcription of the operon will not occur.

Question 11

Which of the following is a real-world example of positive control of gene expression?

Accepted Answer

The maltose operon activated by the maltose activator protein in the presence of maltose.

Question 12

Which of the following is NOT a way that cells can regulate the level of active protein?

Accepted Answer

Direct methylation of DNA bases to degrade proteins.

Question 13

Which of the following statements about gene regulation in Archaea is correct?

Accepted Answer

Archaea use the same transcription machinery as eukaryotes but regulate transcription more like bacteria.

Question 14

Which of the following best explains why some bacterial behaviors, such as biofilm formation, are regulated by quorum sensing?

Accepted Answer

These behaviors are only advantageous at high cell densities, so cells coordinate their activity using signaling molecules.

Question 15

Which of the following is a function of riboswitches in gene regulation?

Accepted Answer

They bind small molecules to alter the secondary structure of mRNA, affecting translation or transcription.

Question 16

A mutation causes the repressor protein of the lac operon to lose its ability to bind the operator. What is the most likely result?

Accepted Answer

The lac operon will be constitutively expressed, regardless of lactose presence.

Question 17

Which of the following is a correct statement about the influenza virus genome?

Accepted Answer

It is altered by antigenic shift and drift, leading to new viral strains.

Question 18

Which of the following best describes the role of a sensor kinase in a two-component system?

Accepted Answer

It detects environmental signals and autophosphorylates, transferring the phosphate to a response regulator.

Question 19

Which of the following is a plausible consequence of a mutation that prevents the formation of inverted repeats in an operator region?

Accepted Answer

Regulatory proteins may not bind efficiently, leading to loss of transcriptional control.

Genetic Regulation and Viral Pathogenesis in Microbiology

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