Question 1

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

Accepted Answer

They require host cell machinery for replication and cannot reproduce outside a host cell.

Question 2

A virus is found to be resistant to drying, acid, and detergents, and is transmitted via the fecal-oral route. Which structural feature most likely explains these properties?

Accepted Answer

Rigid protein capsid without an envelope

Question 3

Which of the following statements about viral envelopes is CORRECT?

Accepted Answer

The envelope is derived from host cell membranes but contains mostly virally encoded proteins.

Question 4

A researcher isolates a virus with a single-stranded, positive-sense RNA genome. Which of the following is TRUE regarding its replication?

Accepted Answer

The viral genome can be directly translated by host ribosomes.

Question 5

Which of the following best explains why most mutations in viral genomes are not beneficial to the virus?

Accepted Answer

Most mutations disrupt essential viral functions required for replication or infectivity.

Question 6

Which of the following is a key difference between DNA and RNA virus replication?

Accepted Answer

RNA viruses require an RNA-dependent RNA polymerase, while DNA viruses use a DNA-dependent DNA polymerase.

Question 7

A virus is found to have a segmented, negative-sense RNA genome. Which of the following must be true for this virus to initiate infection?

Accepted Answer

It must carry an RNA-dependent RNA polymerase within the virion.

Question 8

Which of the following best describes the eclipse period in the viral replication cycle?

Accepted Answer

The period after uncoating when no infectious virus can be detected inside or outside the cell.

Question 9

Which of the following is a function of viral attachment proteins (VAPs)?

Accepted Answer

They mediate the interaction of the virus with the target cell.

Question 10

A patient is infected with a retrovirus. Which of the following steps is unique to the replication of retroviruses compared to other RNA viruses?

Accepted Answer

Synthesis of cDNA from an RNA template by reverse transcriptase.

Question 11

Which of the following best explains why small DNA viruses like parvoviruses can only replicate in actively dividing cells?

Accepted Answer

They rely on the host cell's DNA polymerase and dNTPs, which are abundant only in dividing cells.

Question 12

Which of the following is a consequence of the higher mutation rate of viral polymerases compared to host cell polymerases?

Accepted Answer

Viruses can rapidly evolve resistance to antiviral drugs.

Question 13

Which of the following is TRUE regarding the assembly of viral capsids?

Accepted Answer

Capsids are assembled from individual proteins that associate into larger units such as protomers and capsomeres.

Question 14

Which of the following best describes the Baltimore classification system for viruses?

Accepted Answer

It classifies viruses based on their means of genome replication and the nature of their nucleic acid.

Question 15

A virus is found to be pleomorphic and enveloped, and is inactivated by detergents. Which of the following is the most likely mode of transmission?

Accepted Answer

Respiratory droplets or blood

Question 16

Which of the following is a key reason why viral envelopes must remain intact for the virus to be infectious?

Accepted Answer

The envelope contains viral attachment proteins necessary for entry into host cells.

Question 17

Which of the following best explains why antibodies against viral surface structures can prevent infection?

Accepted Answer

They block the interaction between the virus and the host cell by binding to viral attachment proteins.

Question 18

Which of the following is TRUE regarding the replication of large DNA viruses such as herpesviruses?

Accepted Answer

They often encode their own DNA polymerase and other proteins, making them more independent of the host cell.

Question 19

Which of the following is a characteristic of helical viruses?

Accepted Answer

They have a rod-like appearance and their capsid proteins are arranged in a spiral around the genome.

Viral Classification, Structure, and Replication: Study Notes for Cell Biology

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