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

$$RNA \xrightarrow{\text{RT}} DNA$$

Question 1

Which of the following statements best explains why double-stranded RNA (dsRNA) viruses must carry their own RNA-dependent RNA polymerase (RdRp) into the host cell?

Accepted Answer

Host cells lack RNA-dependent RNA polymerases, which are required for both transcription and replication of the viral genome.

Question 2

During the replication cycle of rotavirus, which of the following events ensures the protection of the viral dsRNA genome from host cell enzymes?

Accepted Answer

The viral nucleocapsid remains intact in the cytoplasm, with replication and transcription occurring inside it.

Question 3

Which of the following best describes the initial step after entry of a +ssRNA virus, such as poliovirus, into a host cell?

Accepted Answer

The viral RNA is used directly as mRNA for translation by host ribosomes.

Question 4

Which enzyme is responsible for synthesizing the complementary RNA strand from the viral genome in both dsRNA and -ssRNA viruses?

Accepted Answer

RNA-dependent RNA polymerase

Question 5

A patient is diagnosed with a viral infection caused by a -ssRNA virus. Which of the following must occur before viral proteins can be synthesized?

Accepted Answer

The -ssRNA genome is converted to +ssRNA by the viral RNA-dependent RNA polymerase.

Question 6

Which of the following viruses is correctly matched with its genome type and replication strategy?

Accepted Answer

Rotavirus: dsRNA; replication and transcription occur within the nucleocapsid in the cytoplasm.

Question 7

Which of the following best explains why retroviruses, such as HIV, are classified as Class VI viruses?

Accepted Answer

They have a +ssRNA genome but replicate through a DNA intermediate using reverse transcriptase.

Question 8

Which of the following is a unique feature of the HIV capsid compared to other animal viruses?

Accepted Answer

It is cone-shaped, an elongated deviation of a spherical icosahedral capsid.

Question 9

A researcher is studying a virus with a segmented -ssRNA genome that replicates in the cytoplasm and requires its own RNA-dependent RNA polymerase. Which virus is the researcher most likely studying?

Accepted Answer

Influenza virus

Question 10

Which of the following best describes the function of the internal ribosome entry site (IRES) in the poliovirus genome?

Accepted Answer

It allows for cap-independent initiation of translation by host ribosomes.

Question 11

Which of the following steps is unique to the replication cycle of retroviruses but not found in other +ssRNA viruses?

Accepted Answer

Reverse transcription of the RNA genome into DNA, followed by integration into the host genome.

Question 12

Which of the following accessory proteins in HIV is responsible for promoting the transport of unspliced RNAs from the nucleus to the cytoplasm?

Accepted Answer

Rev

Question 13

A virus is found to have a non-enveloped, icosahedral structure, a 7.5 kb +ssRNA genome, and is transmitted via the fecal-oral route. Which virus is this most likely to be?

Accepted Answer

Poliovirus

Question 14

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

Accepted Answer

$$RNA \xrightarrow{	ext{RT}} DNA$$

Question 15

Which of the following is a correct sequence of events for the replication of a -ssRNA virus?

Accepted Answer

Entry → Synthesis of +ssRNA by viral polymerase → Translation of +ssRNA → Synthesis of -ssRNA → Assembly

Question 16

Which of the following best explains why dsRNA viruses must keep their genome protected within the nucleocapsid during replication?

Accepted Answer

Host cells have systems to destroy any dsRNA found in the cytoplasm.

Question 17

Which of the following is a function of the HIV accessory protein Nef?

Accepted Answer

Downregulates cellular CD4 and MHC I proteins.

Question 18

Which of the following best describes the process by which the rotavirus genome is replicated?

Accepted Answer

Replication and transcription occur within the nucleocapsid in the cytoplasm, using viral RNA-dependent RNA polymerase.

Question 19

Which of the following is a correct description of the function of the viral protein VPg in poliovirus replication?

Accepted Answer

It acts as a protein primer for replication of the viral genome.

Question 20

Which of the following best explains why the genome of retroviruses does not serve directly as mRNA upon entry into the host cell?

Accepted Answer

The genome is +ssRNA but is first reverse transcribed into DNA, which is then integrated into the host genome before transcription.

Replication Cycles of RNA Viruses

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