Question 1

Which of the following are contributors to viral genome evolution?

Accepted Answer

E

Question 2

Which description of antigenic drift and antigenic shift in the influenza virus is incorrectly matched?

Accepted Answer

Antigenic drift involves minor changes due to mutations in the virus's genes, not reassortment of viral strains. Reassortment, which can lead to a "species jump," is characteristic of antigenic shift, not drift.

Question 3

Viruses are considered to be non- living pathogens for which reason?

Accepted Answer

Viruses are considered non-living because they lack the ability to carry out metabolic processes on their own, which is a fundamental characteristic of life. They require a host cell to perform any metabolic activity.

Question 4

A newly- discovered double- stranded RNA virus which infects animal cells is found to contain a unique enzyme which synthesizes double- stranded RNA using an RNA template. Which of the following statements is likely to be true?

Accepted Answer

Animal cells typically do not have enzymes that synthesize double-stranded RNA from an RNA template; this process is characteristic of some viruses. Therefore, the virus must bring this enzyme into the host cell to replicate its RNA.

Question 5

Which viral family and representative disease contains single- stranded+ RNA and reverse transcriptase?

Accepted Answer

Retroviridae is the viral family that contains single-stranded positive-sense RNA and utilizes reverse transcriptase in its replication cycle. The Human Immunodeficiency Virus (HIV), which causes AIDS, is a prominent example of this family.

Question 6

The key event that occurs during lysogenic replication of bacteriophage that does not occur during lytic replication is

Accepted Answer

In lysogenic replication, the bacteriophage's DNA integrates into the host cell's DNA and replicates along with it, a process that does not occur during lytic replication.

Question 7

Compared to both prokaryotic and eukaryotic cells, viruses

Accepted Answer

Viruses are generally smaller than both prokaryotic and eukaryotic cells, which allows them to infect and replicate within these cells. Unlike cells, viruses do not have the cellular machinery for metabolism or replication on their own and must rely on a host cell. They do contain proteins (in their capsid or envelope) and genetic material (either DNA or RNA), which distinguishes them from the incorrect options listed.

Question 8

A previously undescribed infection has been detected among inhabitants in an isolated village in a remote tropical rainforest. When serum from an infected individual is passed through a filter, the infection can be transmitted to laboratory animals. Nothing is observed when the serum is examined with a light microscope at the highest magnification. Biochemical tests show the presence of RNA and protein but no carbohydrates or lipids. This data is consistent with what type of infectious agent?

Accepted Answer

The ability to pass through a filter and the presence of RNA and protein without carbohydrates or lipids are characteristics of viruses, which are not visible under a light microscope at high magnification due to their small size.

Question 9

Viruses which infect many different tissues types are said to have a(n)

Accepted Answer

Viruses that can infect many different types of tissues exhibit a broad tropism. Tropism refers to the specificity of a virus for a particular host tissue or cell type.

Question 10

Retroviruses use the enzyme reverse transcriptase to

Accepted Answer

Retroviruses, such as HIV, have an RNA genome. They use the enzyme reverse transcriptase to synthesize DNA from their RNA genome, which can then integrate into the host's DNA. This process is unique to retroviruses and is essential for their replication cycle.

Question 11

During lytic replication of bacteriophage, which process uses factors from the host cell, rather than coded by the viral genome?

Accepted Answer

During lytic replication, the bacteriophage relies on the host cell's enzymes for transcription and translation of viral genes, as these processes use the host's ribosomes and other factors.

Question 12

All the following are DNA viruses except

Accepted Answer

Picornaviridae is a family of RNA viruses, not DNA viruses, which includes enteroviruses and rhinoviruses among others.

Question 13

Phage conversion occurs when

Accepted Answer

Phage conversion happens when a prophage (the viral DNA integrated into the bacterial chromosome) confers new properties, including pathogenic traits, to a bacterial cell. This can lead to the bacteria gaining new abilities or becoming more virulent.

Question 14

Which property is not used to classify viruses?

Accepted Answer

Viruses are not classified based on the tissue types they infect. Classification typically involves characteristics such as the presence or absence of an envelope, the type of nucleic acid present, genome architecture, and capsid symmetry.

Question 15

All viruses must use their genome to produce , which is then used by the host cell to produce .

Accepted Answer

Viruses must use their genome to produce mRNA, which is then used by the host cell's machinery to produce proteins. This is a fundamental step in the viral replication process, where the viral genetic material is first transcribed into mRNA before being translated into viral proteins by the host cell's ribosomes.

Question 16

Which genomic arrangement has not been found in viruses?

Accepted Answer

Viruses have been found with single-stranded DNA, double-stranded RNA, single-stranded RNA, and double-stranded DNA. However, a combination of DNA and RNA in the same virus has not been observed in nature. Viruses typically contain either DNA or RNA, not both.

Question 17

Which statement is not true about the virus capsid?

Accepted Answer

The capsid is essential to the virus as it protects the viral genetic material and helps the virus to attach to and enter host cells. Therefore, it can be a useful target for antiviral drugs.

Question 18

Viral spikes

Accepted Answer

Viral spikes are crucial for the virus's ability to infect host cells as they facilitate attachment and entry into host cells, are recognized by the host's immune system as targets, and exhibit specificity by binding to particular structures on the host cell surface.

Question 19

When a virus has an envelope,

Accepted Answer

The answer of When a virus has an envelope,
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Question 20

Which suffix denotes the "order" level of classification for viruses?

Accepted Answer

The suffix "-virales" is used to denote the "order" level of classification in the taxonomy of viruses.

Quiz 6: Viruses and Prions