Question 1

Which of the following best describes why viruses are considered obligate intracellular parasites?

Accepted Answer

They require a host cell's metabolic machinery to replicate and carry out life processes.

Question 2

Which experiment led to the discovery that viruses are distinct from bacteria, as shown in the tobacco mosaic virus studies?

Accepted Answer

Filtered sap from diseased plants, after passing through a filter that traps bacteria, still infected healthy plants.

Question 3

Which of the following structures is NOT found in all viruses?

Accepted Answer

Membranous envelope

Question 4

A bacteriophage injects its DNA into a bacterial cell. Which of the following best describes the next step in the lytic cycle?

Accepted Answer

The host cell's machinery is used to synthesize viral genomes and proteins.

Question 5

Which of the following equations best represents the exponential increase in viral particles during the lytic cycle, assuming each infected cell releases $$n$$ new viruses and $$k$$ cycles occur?

Accepted Answer

$$N = n^k$$

Question 6

What is the main difference between the lytic and lysogenic cycles of bacteriophages?

Accepted Answer

The lytic cycle results in immediate destruction of the host cell, while the lysogenic cycle allows the viral DNA to persist in the host genome without killing the cell.

Question 7

Which of the following best explains how the CRISPR-Cas system provides immunity to bacteria against phages?

Accepted Answer

It integrates fragments of phage DNA into the bacterial genome, which are later transcribed and used to guide Cas proteins to destroy matching phage DNA.

Question 8

Which of the following is a correct statement about the HIV replication cycle?

Accepted Answer

HIV uses reverse transcriptase to convert its RNA genome into DNA, which is then integrated into the host genome as a provirus.

Question 9

Which of the following best describes why influenza viruses can cause pandemics?

Accepted Answer

They have a segmented RNA genome, allowing for reassortment and the emergence of new strains.

Question 10

A patient is diagnosed with a prion disease. Which of the following best explains the mechanism of prion propagation?

Accepted Answer

Prions convert normal host proteins into the misfolded prion form, which accumulates and causes disease.

Question 11

Which of the following is a real-world example of a zoonotic virus that caused a recent pandemic?

Accepted Answer

SARS-CoV-2, which likely originated in bats and caused COVID-19.

Question 12

Which of the following best describes the role of vaccines in viral disease prevention?

Accepted Answer

Vaccines are harmless derivatives of pathogens that stimulate the immune system to mount a defense against the actual pathogen.

Question 13

Which of the following is a unique feature of herpesviruses compared to other viruses?

Accepted Answer

They establish latency in host cells and can reactivate to cause recurrent infections.

Question 14

A plant virus is transmitted from parent to offspring through seeds. What is this mode of transmission called?

Accepted Answer

Vertical transmission

Question 15

Which of the following best explains why antibiotics are ineffective against viral infections?

Accepted Answer

Viruses lack the cellular structures and metabolic pathways targeted by antibiotics.

Question 16

Which of the following is a correct statement about the structure of a bacteriophage?

Accepted Answer

It has a head that contains DNA, a tail sheath, and tail fibers used for attachment to host cells.

Question 17

Which of the following best describes the function of restriction enzymes in bacterial defense against phages?

Accepted Answer

They cut foreign phage DNA, preventing successful infection.

Question 18

Which of the following is a plausible reason why some individuals are resistant to HIV infection?

Accepted Answer

They have a mutation in the CCR5 coreceptor on their helper T cells.

Question 19

Which of the following best describes the process by which viroids cause disease in plants?

Accepted Answer

Viroids are circular RNA molecules that disrupt normal plant growth and development.

LECTURE 22 STUDY GUIDE

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