Question 1

Which of the following best describes the difference between an operon and a regulon in bacterial gene regulation?

Accepted Answer

An operon is a group of genes regulated by the same promoter and transcribed together, while a regulon is a group of genes or operons regulated by the same regulatory protein but may be located at different sites on the chromosome.

Question 2

In the lac operon, what is the effect of allolactose binding to the repressor protein?

Accepted Answer

It causes the repressor to release from the operator, allowing transcription of the operon.

Question 3

Which of the following is a key feature of two-component regulatory systems in bacteria?

Accepted Answer

They involve a sensor kinase that autophosphorylates in response to an environmental signal and transfers the phosphate to a response regulator.

Question 4

Which of the following best explains why quorum sensing is advantageous for pathogenic bacteria?

Accepted Answer

It allows bacteria to coordinate the expression of virulence factors only when the population density is high, increasing the chance of overwhelming host defenses.

Question 5

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

Accepted Answer

Transcription machinery in Archaea is more similar to Eukaryotes, but gene regulation can resemble that of Bacteria.

Question 6

A mutation in the sensor kinase of a two-component system prevents autophosphorylation. What is the most likely outcome?

Accepted Answer

The response regulator will not be phosphorylated, so the target genes will not be regulated in response to the environmental signal.

Question 7

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

Accepted Answer

A repressor protein binds to the operator region, blocking RNA polymerase from transcribing the gene.

Question 8

Which of the following best describes the role of small regulatory RNAs (sRNAs) in bacteria?

Accepted Answer

They can bind to mRNA to either inhibit or enhance translation, depending on the context.

Question 9

Which of the following is true regarding the mechanism of riboswitches?

Accepted Answer

Riboswitches are regulatory segments of mRNA that bind small molecules, causing changes in mRNA structure that affect translation or transcription.

Question 10

A bacterial cell is exposed to a new sugar. The genes for metabolizing this sugar are not expressed until the sugar is present. This is an example of:

Accepted Answer

Enzyme induction

Question 11

Which of the following best describes the function of an activator protein in positive control of gene expression?

Accepted Answer

It binds to a specific DNA site and increases the affinity of RNA polymerase for the promoter, enhancing transcription.

Question 12

Which of the following is a real-world example of global gene regulation in bacteria?

Accepted Answer

The Pho system, which regulates genes involved in phosphate uptake and metabolism in response to phosphate availability.

Question 13

Which of the following best explains why the influenza virus can rapidly change its surface antigens, complicating vaccine design?

Accepted Answer

The segmented genome of influenza allows for reassortment of gene segments during co-infection, leading to antigenic shift.

Question 14

Which of the following is a key step in the life cycle of the Nipah virus that contributes to its pathogenesis in humans?

Accepted Answer

The virus can infect multiple organ systems, including the respiratory and nervous systems, leading to severe disease.

Question 15

Which of the following best describes the mechanism of enzyme repression?

Accepted Answer

A corepressor molecule binds to a repressor protein, enabling it to bind the operator and block transcription.

Question 16

Which of the following is a plausible outcome if a mutation prevents the formation of the operator region in the lac operon?

Accepted Answer

The repressor protein cannot bind, leading to constitutive expression of the lac genes.

Question 17

Which of the following is a function of regulatory RNAs in bacteria?

Accepted Answer

They can modulate translation by base-pairing with target mRNAs, affecting ribosome binding.

Question 18

Which of the following best describes the role of the corepressor in the tryptophan operon?

Accepted Answer

Tryptophan acts as a corepressor by binding to the repressor protein, enabling it to bind the operator and block transcription.

Question 19

Which of the following is a correct statement about the hepatitis viruses discussed?

Accepted Answer

Hepatitis B virus (HBV) can integrate into the host genome, contributing to chronic infection and risk of liver cancer.

Genetic Regulation and Viral Pathogenesis in Microbiology

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