Question 1

Which of the following best describes the function of sigma factors in prokaryotic transcription?

Accepted Answer

They bind to the -10 and -35 regions of the promoter to help RNA polymerase recognize where to begin transcription.

Question 2

A bacterial cell is exposed to both glucose and lactose. Which of the following best describes the state of the lactose operon under these conditions?

Accepted Answer

The operon is repressed because the presence of glucose inhibits cAMP production, preventing CAP from activating transcription.

Question 3

Which enzyme is primarily responsible for synthesizing the leading strand during DNA replication in bacteria?

Accepted Answer

DNA Polymerase III

Question 4

A mutation occurs in the -10 region of a prokaryotic promoter. What is the most likely effect on gene expression?

Accepted Answer

Transcription initiation will be reduced or abolished because RNA polymerase cannot efficiently bind the promoter.

Question 5

Which of the following best describes the difference between monocistronic and polycistronic mRNA?

Accepted Answer

Monocistronic mRNA encodes one protein and is typical of eukaryotes, while polycistronic mRNA encodes multiple proteins and is typical of prokaryotes.

Question 6

A bacterial cell is described as Trp-. What does this mean, and how could this phenotype be used in a laboratory test for carcinogens?

Accepted Answer

The cell cannot synthesize tryptophan and will only grow if tryptophan is supplied; reversion to Trp+ in the presence of a chemical suggests the chemical is a mutagen.

Question 7

Which of the following is a key difference between transformation, transduction, and conjugation in bacterial gene exchange?

Accepted Answer

Transformation involves uptake of naked DNA, transduction involves bacteriophage-mediated DNA transfer, and conjugation requires direct cell-to-cell contact.

Question 8

What is the main function of restriction enzymes in bacteria?

Accepted Answer

They cut foreign DNA at specific sequences, protecting the cell from viral infection.

Question 9

A patient is infected with a virus that has a sense (+) RNA genome. Which of the following statements is true regarding the replication of this virus?

Accepted Answer

The viral RNA can be directly translated by host ribosomes to produce viral proteins.

Question 10

Which of the following best explains how CRISPR-Cas protects bacteria from viral infection?

Accepted Answer

CRISPR sequences store fragments of viral DNA, and Cas9 uses crisprRNA to recognize and cut matching viral DNA during future infections.

Question 11

A temperate bacteriophage infects a bacterial cell and integrates its genome into the host chromosome. What is the integrated phage DNA called, and what is the host cell called after this event?

Accepted Answer

The integrated phage DNA is called a prophage, and the host cell is called a lysogen.

Question 12

Which of the following best describes the role of the spike glycoprotein in SARS-CoV-2 infection?

Accepted Answer

It binds to the ACE2 receptor on host cells, facilitating viral entry.

Question 13

Which of the following is a real-world example of lysogenic conversion?

Accepted Answer

Corynebacterium diphtheriae produces diphtheria toxin only when infected by a lysogenic phage carrying the toxin gene.

Question 14

During the SOS response in bacteria, which DNA polymerase is induced, and what is a key characteristic of this enzyme?

Accepted Answer

DNA polymerase V is induced and is error-prone, allowing replication across damaged DNA.

Question 15

Which of the following best describes the difference between lytic and temperate bacteriophages?

Accepted Answer

Lytic phages immediately replicate and lyse the host cell, while temperate phages can integrate into the host genome and remain dormant.

Question 16

A transposon inserts into the coding region of a gene in a bacterial cell. What is the most likely consequence?

Accepted Answer

The gene's function is disrupted, potentially leading to a loss-of-function mutation.

Question 17

Which of the following best explains why a bacterial cell might use DNA polymerase V during the SOS response instead of DNA polymerase III?

Accepted Answer

DNA polymerase V can synthesize DNA across damaged templates, even if it introduces mutations, allowing the cell to survive severe DNA damage.

Question 18

Which of the following statements about animal virus infections is correct?

Accepted Answer

Herpesvirus establishes a latent persistent infection, while HIV establishes a chronic persistent infection.

Question 19

Which of the following best describes the role of TMPRSS2 in SARS-CoV-2 infection?

Accepted Answer

It cleaves the spike protein, enabling fusion of the viral and host cell membranes.

Question 20

A researcher is studying a bacterial population and observes that some cells can take up naked DNA from the environment. What term best describes these cells, and what is a common cause of this ability?

Accepted Answer

They are competent, often due to the expression of specific membrane proteins that facilitate DNA uptake.

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