Question 1

Which of the following best describes why viruses are considered to exist in a 'shady area' between life-forms and chemicals?

Accepted Answer

Viruses require a host cell to replicate but possess genetic material like living organisms.

Question 2

A virus with a single-stranded RNA genome that can be directly translated into protein upon infection is best classified as:

Accepted Answer

A positive-sense RNA virus

Question 3

Which of the following statements about viral envelopes is TRUE?

Accepted Answer

Viral envelopes help animal viruses enter host cells by fusing with the host's plasma membrane.

Question 4

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

Accepted Answer

The lytic cycle results in the destruction of the host cell, while the lysogenic cycle allows the host cell to survive and replicate with the viral DNA.

Question 5

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

Accepted Answer

Viruses lack the metabolic pathways targeted by antibiotics.

Question 6

A patient is infected with HIV, a retrovirus. Which enzyme is essential for the replication of HIV within the host cell?

Accepted Answer

Reverse transcriptase

Question 7

Which of the following is a function of the CRISPR-Cas system in bacteria?

Accepted Answer

It protects bacteria by recognizing and degrading foreign phage DNA.

Question 8

A new viral disease emerges in a remote village and quickly spreads worldwide. Which of the following is NOT a likely contributing factor to the emergence of this viral disease?

Accepted Answer

Use of antibiotics to treat viral infections

Question 9

Which of the following best describes the role of the CCR5 protein in HIV infection?

Accepted Answer

CCR5 is a co-receptor on host cells that allows HIV to enter most cells.

Question 10

Which of the following is a plausible reason why prion diseases are so difficult to treat?

Accepted Answer

Prions are misfolded proteins that induce misfolding in normal proteins and are virtually indestructible.

Question 11

A plant virus is transmitted from an infected parent plant to its offspring. This is an example of:

Accepted Answer

Vertical transmission

Question 12

Which of the following best explains why vaccines are effective in preventing viral diseases?

Accepted Answer

Vaccines stimulate the immune system to recognize and respond to the pathogen.

Question 13

Which of the following is a correct sequence of events in the lytic cycle of a bacteriophage?

Accepted Answer

Attachment → Entry of DNA → Synthesis of viral components → Self-assembly → Release

Question 14

Which of the following is a real-world example of a virus that uses an animal vector for transmission?

Accepted Answer

Zika virus transmitted by mosquitoes

Question 15

Which of the following best describes the process by which a retrovirus integrates its genetic material into the host genome?

Accepted Answer

The viral RNA is reverse transcribed into DNA, which is then integrated into the host genome.

Question 16

Which of the following is a likely consequence of environmental changes such as deforestation on the emergence of viral diseases?

Accepted Answer

Increased opportunities for viruses to jump from animal hosts to humans

Question 17

Which of the following is a distinguishing feature of prions compared to viruses?

Accepted Answer

Prions are infectious proteins without nucleic acids.

Question 18

A scientist discovers a new virus that can only infect a single species of frog and only targets its liver cells. This is an example of:

Accepted Answer

A narrow host range and tissue specificity

Question 19

Which of the following best explains why multidrug treatments are considered most effective against HIV?

Accepted Answer

HIV mutates rapidly, so using multiple drugs reduces the chance of resistance.

Question 20

Which of the following is a correct statement about the role of restriction enzymes in bacterial defense against phages?

Accepted Answer

Restriction enzymes recognize and cut foreign phage DNA, protecting the bacterium.

Viruses: Structure, Replication, and Impact

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