Q: Which of the following equations correctly represents the action of reverse transcriptase in retroviruses?

$$\mathrm{RNA} \xrightarrow{\text{reverse transcriptase}} \mathrm{DNA}$$

Question 1

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

Accepted Answer

They require host cell machinery to replicate their genome and produce new virions.

Question 2

A virus with a segmented, single-stranded, negative-sense RNA genome is most likely classified in which viral family?

Accepted Answer

Orthomyxoviridae

Question 3

Which of the following best describes the process of antigenic shift in influenza viruses?

Accepted Answer

A major change in surface glycoproteins due to gene reassortment between different viral strains.

Question 4

During the lytic replication cycle of a bacteriophage, what is the 'burst size'?

Accepted Answer

The number of new virions released from a lysed bacterial cell.

Question 5

Which enzyme is unique to retroviruses and is responsible for synthesizing DNA from an RNA template?

Accepted Answer

Reverse transcriptase

Question 6

A patient is diagnosed with a prion disease. Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that cause normal cellular PrP to refold into a disease-causing form.

Question 7

Which of the following is a mechanism by which viruses can cause cancer?

Accepted Answer

Inserting their genome into a tumor suppressor gene, disrupting its function.

Question 8

Which of the following best describes the genome of the Human Immunodeficiency Virus (HIV)?

Accepted Answer

Two copies of single-stranded RNA

Question 9

Which of the following is NOT a characteristic of viroids?

Accepted Answer

They code for their own proteins.

Question 10

Which step in the replication of an enveloped animal virus is responsible for the persistent nature of some viral infections?

Accepted Answer

Budding from the host cell membrane

Question 11

Which of the following equations correctly represents the action of reverse transcriptase in retroviruses?

Accepted Answer

$$\mathrm{RNA} \xrightarrow{	ext{reverse transcriptase}} \mathrm{DNA}$$

Question 12

Which of the following viruses is associated with the development of cervical cancer?

Accepted Answer

Human papillomavirus (HPV)

Question 13

A scientist isolates a virus with a helical capsid, an envelope, and a genome consisting of eight segments of single-stranded, negative-sense RNA. Which virus is this most likely to be?

Accepted Answer

Influenza virus

Question 14

Which of the following best explains why enveloped viruses are generally more sensitive to environmental conditions than non-enveloped viruses?

Accepted Answer

Their phospholipid bilayer envelope is easily disrupted by detergents and drying.

Question 15

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

Accepted Answer

Attachment → Entry → Synthesis → Assembly → Release

Question 16

Which of the following is a unique feature of prion diseases compared to viral diseases?

Accepted Answer

They are caused by infectious proteins with abnormal folding.

Question 17

Which of the following best describes the role of integrase in the HIV replication cycle?

Accepted Answer

It integrates viral DNA into the host cell genome.

Question 18

Which of the following is a plausible reason why a virus might have a narrow host range?

Accepted Answer

Its surface proteins only bind to specific receptors found on certain host cells.

Question 19

Which of the following best describes the difference between lysogenic and lytic replication cycles in bacteriophages?

Accepted Answer

Lysogenic cycles involve integration of viral DNA into the host genome, while lytic cycles result in immediate host cell lysis.

Viruses, Viroids, and Prions: Structure, Replication, and Pathogenicity

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