Question 1

Which of the following best describes the role of a capsid in a virus?

Accepted Answer

It is the protein coat that covers the viral genome and may take many different forms.

Question 2

A bacteriophage infects a bacterial cell and integrates its DNA into the host genome without killing the cell. What is this process called?

Accepted Answer

Lysogenic cycle

Question 3

Which enzyme is essential for the replication of retroviruses, such as HIV, and what is its function?

Accepted Answer

Reverse transcriptase; it catalyzes the transcription of RNA to DNA

Question 4

Which of the following viral genomes requires host ribosomes for immediate translation upon entry into the cytoplasm?

Accepted Answer

Positive-sense single-stranded RNA ($$+ssRNA)$$

Question 5

A patient is infected with a virus that uses reverse transcriptase to integrate its genome into the host's DNA. Which type of viral genome does this virus most likely possess?

Accepted Answer

Single-stranded RNA (reverse transcriptase) ($$ssRNA-RT)$$

Question 6

Which of the following statements about viroids is correct?

Accepted Answer

Viroids are small, circular, single-stranded RNA molecules that do not encode proteins but replicate using host enzymes.

Question 7

During the lytic cycle of a bacteriophage, which of the following events occurs?

Accepted Answer

The phage inserts its DNA, degrades host DNA, and synthesizes viral components.

Question 8

Which of the following best explains why restriction enzymes are important in bacterial defense against viruses?

Accepted Answer

They degrade viral DNA, preventing replication of the virus.

Question 9

A virus with a double-stranded RNA genome replicates in the cytoplasm. Which enzyme is primarily responsible for its genome replication?

Accepted Answer

Viral RNA polymerase

Question 10

Which of the following is a correct application of the central dogma of molecular biology in the context of viral replication?

Accepted Answer

$$DNA \rightarrow RNA \rightarrow Protein$$

Question 11

A negative-sense RNA virus must first undergo which process before its genome can be translated by host ribosomes?

Accepted Answer

Transcription by viral RNA polymerase to produce complementary positive-sense RNA

Question 12

Which of the following best describes a prion?

Accepted Answer

An infectious self-propagating protein that causes brain diseases in animals

Question 13

Which of the following viruses would use host DNA polymerase for replication?

Accepted Answer

Double-stranded DNA virus ($$dsDNA)$$

Question 14

A scientist discovers a new virus that contains single-stranded DNA and replicates in the nucleus. Which enzyme is most likely required for its replication?

Accepted Answer

Host DNA polymerase

Question 15

Which of the following is a distinguishing feature of temperate phages compared to virulent phages?

Accepted Answer

Temperate phages can replicate through both the lytic and lysogenic cycles.

Question 16

Which step in the HIV replication cycle is unique compared to most other animal viruses?

Accepted Answer

Reverse transcription of viral RNA into DNA

Question 17

A virus with a lipid envelope and embedded glycoproteins is most likely to infect which type of host cell?

Accepted Answer

Animal cell

Question 18

Which of the following best explains why prion diseases are difficult to treat?

Accepted Answer

Prions do not contain nucleic acids and are resistant to standard sterilization methods.

Question 19

A plant is infected by an agent that consists only of a short, circular RNA molecule and does not encode any proteins. What is this agent?

Accepted Answer

Viroid

Question 20

Which of the following equations correctly represents reverse transcription in retroviruses?

Accepted Answer

$$RNA \rightarrow DNA$$

Characterizing and Classifying Viruses, Viroids, and Prions

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