Deck 6: Viruses and Prions

Question 1

Which of the following are contributors to viral genome evolution?

A) quick replication time
B) quick replication time and superior proofreading by RNA polymerases compared to DNA polymerases
C) superior proofreading by RNA polymerases compared to DNA polymerases
D) the large number of virions released within a host
E) quick replication time and the large number of virions released within a host

Answer 1

quick replication time and the large number of virions released within a host

Question 2

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

A) Antigenic shift: Often leads to viral strains with new features such as increased infectivity or expanded host range.
B) Antigenic drift: Spontaneous mutation leads to a minor change in HA or NA spikes.
C) Antigenic shift: May result in a pandemic outbreak due to widespread lack of immunity.
D) Antigenic drift: A host vaccinated against an influenza strain before antigenic drift may lack effective immunity and be susceptible to infection.
E) Antigenic drift: Often involves reassortment of viral strains in an animal host followed by a "species jump" to humans.

Answer 2

Antigenic drift: Often involves reassortment of viral strains in an animal host followed by a "species jump" to humans.

Question 3

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

A) their lack of metabolic processes
B) their extremely small size
C) their unique type of cells
D) their unique type of cells and their lack of metabolic processes
E) their ability to synthesize only some of their own components

Answer 3

their lack of metabolic processes

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?

A) This enzyme would not be a good antiviral drug target as the host cell likely has a similar enzyme which could be affected by such a drug.
B) The enzyme probably came from the host animal cell and is coded for by a gene in the host cell.
C) This enzyme is coded for by a gene in the host cell.
D) The enzyme probably came from the host animal cell.
E) The virus must bring this enzyme into the host cell as synthesizing RNA from an RNA template does not happen in animal cells.

Question 5

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

A) Orthomyxoviridae (influenza)
B) Retroviridae (AIDS)
C) Filoviridae (Ebola)
D) Paramyxoviridae (measles)
E) Rhabdoviridae (rabies)

Question 6

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

A) release of mature viral particles by lysis of the bacterial cell.
B) penetration of the phage DNA into the host cell.
C) attachment of the phage to specific proteins in the bacterial cell.
D) integration of the phage DNA into the host cell DNA.
E) assembly of new phage by packing viral genomes into capsids.

Question 7

Compared to both prokaryotic and eukaryotic cells, viruses

A) are generally smaller.
B) lack proteins.
C) lack genetic material.
D) have similar metabolic processes.
E) are not filterable.

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?

A) virus
B) prokaryote
C) eukaryote
D) either a virus or a prokaryote
E) either a virus, a prokaryote, or a eukaryote

Question 9

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

A) narrow host range.
B) broad tropism.
C) narrow tropism.
D) indeterminate host range.
E) broad host range.

Question 10

Retroviruses use the enzyme reverse transcriptase to

A) transcribe mRNA from a DNA genome.
B) direct the production of DNA from a single- stranded RNA genome.
C) synthesize a hybrid molecule with one DNA stranded base- paired to the complementary RNA strand.
D) synthesize sense- stranded mRNA from an antisense RNA genome.
E) synthesize double- stranded RNA.

Question 11

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

A) proteins to copy the viral genome
B) DNAases to break up the host cell genome
C) proteins to build new phage particles
D) enzymes which transcribe and translate viral genes
E) lysozyme to rupture the host cell

Question 12

All the following are DNA viruses except

A) Papillomaviridae.
B) Picornaviridae.
C) Adenoviridae.
D) Herpeseviridae.
E) Hepadnaviridae.

Question 13

Phage conversion occurs when

A) a host cell is infected by a bacteriophage.
B) prophage confer new pathogenic properties on bacterial cells.
C) bacteriophage are released from the host cell.
D) prophase excise themselves and resume lytic replication when the host cell is stressed.
E) bacteriophage are used clinically to treat bacterial infections.

Question 14

Which property is not used to classify viruses?

A) tissue types infected
B) presence or absence of an envelope
C) type of nucleic acid present
D) genome architecture
E) capsid symmetry

Question 15

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

A) DNA; proteins
B) proteins; DNA
C) mRNA; proteins
D) proteins; mRNA
E) DNA; mRNA

Question 16

Which genomic arrangement has not been found in viruses?

A) single- stranded DNA
B) double- stranded RNA
C) a combination of DNA and RNA in the same virus
D) single- stranded RNA
E) double- stranded DNA

Question 17

Which statement is not true about the virus capsid?

A) Because the capsid is not essential to the virus, it is not a useful target for antiviral drugs.
B) The capsid is made of one or more types of protein subunits.
C) Both bacteriophage and animal viruses have capsids.
D) The capsid determines the shape of the virus.
E) The capsid functions as a package for the viral genetic material.

Question 18

Viral spikes

A) allow the virus to attach and enter host cells.
B) may be a target for the host immune system.
C) allow the virus to attach and enter host cells, may be a target for the host immune system, and show specificity in binding to particular structures on the host cell.
D) allow the virus to attach and enter host cells but do not show specificity for a particular structure on the host cell.
E) show specificity in binding to particular structures on the host cell.

Question 19

When a virus has an envelope,

A) it may escape its host cell either by budding or by lysis.
B) it is always a bacteriophage.
C) it is always an RNA- containing virus.
D) it likely escapes its host cell by lysis.
E) it likely escapes its host cell by budding.

Question 20

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

A) - virion
B) - viridae
C) - virus
D) - virales
E) Viruses are not classified to the "order" level.

Question 21

Which of the following antiviral drug categories is incorrectly matched with its description?

A) Proteases: Target protein- cutting enzymes which make mature virons
B) Nucleoside analogs: Mimic normal nucleotides interfering with nucleic acid replication
C) Antisense antivirals: Short sequences of nucleotides that are complementary to viral RNA
D) Nucleotide reverse transcriptase inhibitors: Target retroviruses
E) Interferons: Used for postexposure prophylaxis

Question 22

When mixed with their host bacterium and plated on solid agar, lytic phage will form clear areas in the bacterial growth. What are these clear areas called?

A) plaques
B) zones of inhibition
C) assays
D) titers
E) halos

Question 23

Which stage of animal virus replication will not be different between naked viruses and enveloped viruses?

A) release
B) replication
C) penetration
D) assembly
E) uncoating

Question 24

The shape of a virus may be determined by either its capsid or its envelope.

Question 25

Oncogenic viruses

A) stimulate uncontrolled host cell division.
B) increase host cell responsiveness to death signals.
C) are never RNA viruses.
D) always integrate into the host cell DNA.
E) suppress the host immune system.

Question 26

Animal viruses can be grown in all of the following except

A) embryonated eggs.
B) tissue culture.
C) E. coli cells.
D) live animal hosts.
E) HeLa cells.

Question 27

Challenges in developing effective antiviral drugs with minimal side effects to the patient include

A) drugs can be easily delivered to reach viruses within host cells.
B) viruses have many more chemically distinct targets than living pathogens.
C) only the attachment stage of the viral life cycle is a suitable target for antiviral drug action.
D) the immune system is rarely successful in ending viral infections so there is no natural model to work from.
E) viruses use the cell's own machinery and metabolism for replication.

Question 28

Which statement is not true about chronic persistent viral infections?

A) The immune system fails to clear the infection.
B) May involve periods of flare- up where the virus is actively replicating alternating with periods of dormancy.
C) A period of quiet infection where the host is asymptomatic is followed by a period of active viral replication.
D) May involve integration of the virus into the host cell DNA to form a provirus.
E) Small numbers of virions may be produced and released from host cells during the quiet periods.

Question 29

Which is not a cancer linked to a specific virus?

A) adult T- cell leukemia
B) cervical cancer
C) skin cancer
D) liver cancer
E) Kaposi sarcoma

Question 30

HIV, the virus which causes AIDS, interacts with two receptors on the host cell membrane: CD4 and CCR5. A small percentage of individuals have a genetic mutation which causes their cells to lack CCR5. These individuals will never develop AIDS nor are they able to pass HIV on to others. Which part of viral replication is being blocked by the lack of a receptor?

A) The host cell enzymes are unable to replicate the HIV genome.
B) The virus components cannot be assembled into new virions.
C) Endocytosis is being prevented.
D) HIV cannot attach to the host cell without the proper membrane receptor.
E) Newly assembled virions cannot be released from the host cell.

Question 31

Which of the following prion diseases may be acquired by eating beef contaminated with a cattle prion?

A) variant CJD
B) sporadic CJD
C) inherited CJD
D) Gerstmann- Straussler- Schienker syndrome
E) iatrogenic CJD

Question 32

Which type of viral infection is demonstrated by the graph?

A) chronic persistent
B) acute non- persistent
C) latent persistent
D) lysogenic
E) acute persistent

Question 33

Which of the following tests works by detecting viral nucleic acid?

A) Agglutination with beads coated with either antibodies or antigens
B) PCR
C) Agglutination with beads coated with antibodies to the virus
D) Agglutination with beads coated with viral antigens
E) ELISA

Question 34

Prions are

A) associated with many tissue types.
B) living, acellular entities.
C) diagnosed with a simple blood test.
D) misfolded proteins which can cause normal versions to also misfold.
E) infectious nucleic acids.

Question 35

Which stage of viral replication is shown?

A) penetration via membrane fusion
B) release by budding
C) penetration via endocytosis
D) release by lysis
E) attachment

Question 36

Both viruses and prokaryotes reproduce by binary fission.

Question 37

An individual uses an in- home test kit one week after engaging in high- risk behavior for HIV infection. The test kit uses a saliva sample that is mailed to a lab where an agglutination test to detected HIV antibodies is run. The results come back negative for HIV. What should the patient consider regarding these test results?

A) Agglutination tests will not detect viruses if the infection is latent.
B) One week may not be enough time for HIV antibodies to be detected.
C) An ELISA test is needed to detect the presence of HIV nucleic acid.
D) Agglutination tests are not appropriate for testing samples of body fluids.
E) Agglutination tests will not detect viruses if the infection is latent, nor are they appropriate for testing samples of body fluids.

Question 38

What does the plaque assay determine?

A) if the virus can grow in a live animal host
B) number of bacteriophage in a sample
C) if the phage is a lysogenic phage
D) type of bacteriophage in a sample
E) if a given drug will be useful in treating a given viral infection

Question 39

One ml of a liquid suspension of bacteriophage is mixed with its host bacteria and plated. After incubation, the plate is completely clear. What is the probable explanation?

A) The bacteria mutated and could no longer be infected by this phage.
B) The bacteriophage doesn't grow on the type of agar used.
C) The bacteriophage culture was dead.
D) The phage concentration was so high that all the host bacterial cells were killed.
E) The phage concentration was too low to infect many bacterial cells.

Question 40

Which stage of animal virus replication may be blocked by a drug that binds with the viral spike?

A) penetration
B) replication
C) attachment
D) assembly
E) uncoating

Question 41

All persistent viral infections occur when the virus integrates into the host cell DNA to form a provirus.

Question 42

Describe the lytic and lysogenic bacteriophage replication cycles.

Question 43

Antiviral drugs exist that target all stages of viral replication except the production of viral nucleic acids.

Question 44

Like bacteriophage, when an animal cell virus enters a host cell, only the genome enters while the capsid remains outside the cell.

Question 45

Naked viruses usually exit the animal host cell by budding while enveloped viruses exit by lysis.

Question 46

Both agglutination and ELISA procedures may be used to detect the presences of either viral antigen or the patient's antibodies to a virus.

Question 47

Select three points in the viral replication process and describe how an antiviral drug may be used to target that point. Provide the name of one drug or drug family that targets the steps you chose.

Question 48

Use the concepts of antigenic drift and antigenic shift to describe why influenza causes both "routine" seasonal outbreaks as well as to periodically cause more serious global outbreaks, or pandemics.

Question 49

The number of species that a specific virus infects is called its host range while the types of tissues that the virus infects is called tropism.