Question 1

Which of the following best describes a virus?

Accepted Answer

A non-cellular infectious agent that requires a host cell for replication

Question 2

Which component of a virus is primarily responsible for recognizing and binding to host cell receptors?

Accepted Answer

Envelope glycoproteins

Question 3

A researcher is studying a virus with icosahedral symmetry, an envelope, and reverse transcriptase. Which of the following statements is most accurate about this virus?

Accepted Answer

It can synthesize DNA from an RNA template

Question 4

Which laboratory technique is most appropriate for quantifying the number of infectious viral particles in a sample?

Accepted Answer

Plaque assay

Question 5

During the lytic cycle of phage T4, which event occurs immediately after viral DNA injection into the host cell?

Accepted Answer

Transcription and translation of early viral genes

Question 6

Which of the following best distinguishes the lysogenic cycle from the lytic cycle in bacteriophage lambda?

Accepted Answer

The lysogenic cycle involves integration of viral DNA into the host genome as a prophage

Question 7

A patient is infected with a virus that forms a provirus in their genome. Which of the following is most likely true about this virus?

Accepted Answer

It can integrate its genetic material into the host cell's DNA

Question 8

According to the Baltimore classification scheme, which type of virus requires the enzyme RNA-dependent RNA polymerase for genome replication?

Accepted Answer

Class III: Double-stranded RNA viruses

Question 9

Which of the following best describes the replication strategy of the single-stranded DNA virus M13?

Accepted Answer

It uses host DNA polymerase to synthesize a complementary DNA strand, forming a double-stranded replicative form

Question 10

Which of the following steps is unique to the replication of double-stranded DNA phage lambda compared to single-stranded DNA phage M13?

Accepted Answer

Integration of viral DNA into the host genome as a prophage

Question 11

A scientist observes that a virus can only infect cells that express a specific surface protein. Which viral component is most likely responsible for this host specificity?

Accepted Answer

Viral envelope glycoproteins

Question 12

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

Accepted Answer

They require host cell machinery for replication and metabolism

Question 13

A viral genome is classified as Class VI in the Baltimore scheme. Which of the following statements is correct about its replication?

Accepted Answer

It uses reverse transcriptase to synthesize DNA from an RNA template

Question 14

Which of the following equations best represents the calculation of viral titer using a plaque assay?

Accepted Answer

$$	ext{Viral\ titer} = \frac{	ext{Number\ of\ plaques}}{	ext{Dilution\ factor} 	imes 	ext{Volume\ plated\ (mL)}}$$

Question 15

A virus is found to have a helical capsid, an envelope, and a negative-sense RNA genome. According to the Baltimore classification, which class does this virus belong to?

Accepted Answer

Class V

Question 16

Which of the following best describes the process of viral assembly in eukaryotic cells?

Accepted Answer

Viral proteins and genomes self-assemble into new virions, often in the cytoplasm or nucleus

Question 17

A patient is diagnosed with a viral infection. The virus is found to be released from the host cell by budding. Which of the following is most likely true about this virus?

Accepted Answer

It acquires its envelope from the host cell membrane during release

Question 18

Which of the following is a key difference between the replication of phage T4 and phage lambda?

Accepted Answer

Phage lambda can enter a lysogenic cycle, while phage T4 is strictly lytic

Question 19

A virologist is studying a new virus and determines that it lacks an envelope, has icosahedral symmetry, and contains double-stranded DNA. Which of the following is most likely true about this virus?

Accepted Answer

It is likely to be stable in harsh environmental conditions

Question 20

Which of the following best explains why single-stranded DNA viruses like M13 require the formation of a double-stranded replicative form during replication?

Accepted Answer

Host DNA polymerase can only synthesize DNA using a double-stranded template

Viruses: Structure, Replication, and Classification

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