Deck 5: Viruses

Question 1

What is the most common way for enveloped viruses to enter animal cells?

A) The virion fuses itself to the cell membrane.
B) The virion directly injects its nucleic acid.
C) Endocytosis of the virion.
D) Through lysis of the cell.
E) Via a hole in the cell membrane.

Answer 1

A

Question 2

What is the viral capsid composed of?

A) protein
B) nucleic acid
C) lipid
D) polysaccharide
E) glycogen

Answer 2

A

Question 3

Enveloped viruses are mainly associated with which of the following?

A) plants and bacteria
B) animals
C) bacteria
D) plant and animals
E) plants

Answer 3

B

Question 4

What is the most common way for non-enveloped viruses to enter animal cells?

A) The virion fuses itself to the cell membrane.
B) The virion directly injects its nucleic acid.
C) Endocytosis of the virion.
D) Through lysis of the cell.
E) Via a hole in the cell membrane.

Question 5

What is the premise of the coevolution hypothesis of viral evolution?

A) Viruses appeared after the first cells were well established.
B) Viruses arose from excess DNA of cells.
C) Viruses first appeared before or at the same time as the first primordial cells.
D) Viruses first appeared about a million years ago and continue to evolve along with their hosts.
E) Viruses originated when some cells lost the ability to replicate on their own.

Question 6

What general shape is a virus with helical capsid symmetry?

A) icosahedral
B) spherical
C) round
D) rod shaped
E) square

Question 7

What protective structure contains the viral nucleic acid?

A) envelope
B) nucleus
C) capsid
D) endosome
E) vacuole

Question 8

Which of these findings supports the progressive hypothesis of viral origin?

A) The presence of mitochondria and chloroplast in cells.
B) The existence of obligate intracellular pathogens like Chlamydia.
C) The discovery of nucleocytoplasmic large DNA viruses.
D) The existence of eukaryal transposons or retrotransposon genetic elements.
E) The presence of a nucleus in eukaryotic cells.

Question 9

What is the first step in the viral replication cycle?

A) RNA synthesis
B) genome synthesis
C) entry into the cell
D) attachment to the cell
E) viral RNA translation

Question 10

Many enveloped viruses exit their host cell through a process called _________.

A) exocytosis
B) budding
C) cell lysis
D) receptor-mediated endocytosis
E) phagocytosis

Question 11

A single virus-infected cell may produce up to __________ new virions.

A) 10
B) 100
C) 1000
D) 10,000
E) one million

Question 12

What technique is usually used for the quantification of a bacteriophage suspension?

A) a direct count
B) a plaque assay
C) a protein-based assay
D) a loop dilution assay
E) a PCR assay

Question 13

What is the premise of the progressive hypothesis of viral origin?

A) Viruses evolved from symbionts of cells.
B) Viruses evolved from self-replicating nucleic acid segments.
C) Viruses originated from cells that lost the ability to replicate.
D) Viruses were present when the first primordial cells evolved.
E) Viruses arose from fragmented DNA in a cell.

Question 14

What is the average size of a virus?

A) 10 - 100 nm
B) 0.5 - 1 µm
C) 5 - 10 µm
D) 100 - 500 µm.
E) 1 - 10 mm

Question 15

Plant viruses often enter into a plant cell:

A) through fusion of the virion to the cell membrane.
B) through direct injection of the viral nucleic acid.
C) as a result of insects feeding on the plant.
D) by endocytosis.
E) by phagocytosis.

Question 16

Viruses that have icosahedral symmetry have ________ faces and 12 vertices resulting in a spherical appearance.

A) 10
B) 20
C) 30
D) 40
E) 50

Question 17

The field of virology started in the late _______ after Dimitri Ivanovski demonstrated that the infectious agent that caused disease in a tobacco plants could pass through a filter small enough to exclude any known bacterium.

A) 1500s
B) 1600s
C) 1700s
D) 1800s
E) 1900s

Question 18

Which of these comprises the viral genome?

A) single-stranded DNA
B) single-stranded RNA
C) double-stranded DNA
D) double-stranded RNA
E) All of these choices are seen in viruses.

Question 19

How do bacteriophages invade the bacteria cell?

A) The bacteriophage fuses itself to the cell membrane.
B) The bacteriophage directly injects its nucleic acid.
C) Endocytosis of the bacteriophage.
D) Through lysis of the cell.
E) Via a hole in the cell membrane.

Question 20

Most viruses with helical capsid symmetry contain _______ as their nucleic acid.

A) single-stranded DNA
B) single-stranded RNA
C) double-stranded DNA
D) double-stranded RNA
E) RNA/DNA dimer

Question 21

What is a prion?

A) An infectious RNA particle.
B) A particle similar to a satellite virus.
C) An infectious DNA particle.
D) An infectious protein particle.
E) A type of virus.

Question 22

Viruses have been used extensively to further our knowledge on the molecular biology of the human cell.

Question 23

The discovery of oncogenes in this virus group led to the discovery of proto-oncogenes in human cells and an understanding of how tumors form.

A) Poliovirus
B) Retrovirus
C) Rhinovirus
D) Orthomyxovirus
E) Paramyxovirus

Question 24

Enveloped viruses acquire their envelope from host cell membranes.

Question 25

Viroids are infectious RNA particles that cause infections in:

A) plants and animals.
B) animals.
C) bacteria and plants.
D) plants
E) bacteria.

Question 26

Which Domain contains the viruses?

A) Bacteria
B) Archaea
C) Eukarya
D) It depends upon their host.
E) They are not classified at the domain level.

Question 27

Term for bacteriophages that have the ability to either cause a lytic infection or integrate their genome into the host cell chromosome after entry into the host cell.

A) lysogenic phage
B) virulent phage
C) transposable phage
D) cytopathic phage
E) retro-phage

Question 28

Why is the human hepatitis delta virus similar to satellite viruses of plants?

A) It has a similar nucleic acid sequence.
B) It can also cause an infection in plants.
C) It requires a helper virus for replication in the cell.
D) It is a single-stranded DNA virus.
E) It is related to the retroviruses.

Question 29

Which of these causes transmissible spongiform encephalopathies?

A) viroids
B) satellite viruses
C) the human delta virus
D) prions
E) satellite RNAs

Question 30

The International Committee on Taxonomy of Viruses (ICTV)classification scheme uses all of the following criteria to classify viruses EXCEPT:

A) the host they infect.
B) the type of nucleic acid they contain.
C) ribosomal RNA sequence.
D) virion morphology.
E) presence of absence of an envelope.

Question 31

What is the Baltimore classification scheme for viruses based on?

A) strandedness and type of nucleic acid
B) type of virion symmetry
C) type of capsid found in the virion
D) type of host the virus infects
E) the presence or absence of an envelope

Question 32

All viruses that cause hepatitis in humans belong to the same virus family.

Question 33

What do proto-oncogenes encode?

A) proteins that cause cell death
B) proteins that cause apoptosis in the cell
C) proteins that control cell division
D) proteins that prevent virus infection
E) retroviral proteins

Question 34

All viruses require host cell enzymes for translation.

Question 35

How do prions cause disease?

A) By corrupting mRNA expression in the cell.
B) By corrupting DNA replication in the cell.
C) By preventing translation from occurring in the cell.
D) By causing naturally occurring proteins in the cell to change shape.
E) By preventing proper RNA transcription termination.

Question 36

All of the following methods can be used to quantify viruses EXCEPT:

A) plaque assay.
B) hemagglutinin assay.
C) viral protein assay.
D) endpoint assay to determine LD₅₀.
E) endpoint assay to determine ID₅₀.

Question 37

Filtration of a bacteriophage preparation replicated in E.coli will effectively separate viable cells from phage particles.

Question 38

Electron microscopy is the most precise way to identify an unknown virus.

Question 39

The term for bacteriophage DNA that has integrated into the host cell chromosome and replicates along with the host cell chromosome.

A) a plasmid
B) a transposon
C) a prophage
D) a lysogen
E) a retrophage

Question 40

Which method listed below would provide the most reliable information for the identification of an unknown virus?

A) electron microscopy
B) hemagglutinin assay
C) plaque assay
D) antibody titer assay
E) viral nucleic acid analysis

Question 41

Infectious protein particles that cause diseases like Creutzfeldt-Jakob disease are called ________.

Question 42

The zone of clearing as a result of a phage infection on a lawn of E.coli growing on the surface of an agar plate is called a ________.

Question 43

Genes that are involved in the normal regulation of the cell cycle and can be altered to increase probability of cancer are called ___________.

Question 44

Small infectious RNA molecules that are able to cause disease in plants are called ________.

Question 45

Viruses are currently being used for gene therapy as the agent for delivery of the gene to the appropriate cell.

Question 46

The ICTV virus classification scheme uses a number of viral attributes for the grouping of viruses into orders,families,genera,and species.List the viral features used to classify viruses using this scheme.

Question 47

A bacterial strain that contains a phage genome integrated into its chromosome is called a _________.

Question 48

What is a prophage and how is the prophage established in a bacterial cell?

Question 49

Describe the coevolution hypothesis of viral origin.What evidence supports this hypothesis?