Deck 13: Viruses, Viroids, and Prions

Question 1

Which of the following is necessary for replication of a prion?

A) RNA
B) DNA polymerase
C) lysozyme
D) PrPSc
E) DNA

Answer 1

D

Question 2

Which of the following statements about viral spikes is FALSE?

A) They bind to receptors on the host cell surface.
B) They are composed of carbohydrate-protein complexes.
C) They may cause hemagglutination.
D) They are found only on nonenveloped viruses.
E) They are used for attachment.

Answer 2

D

Question 3

Which of the following is NOT used as a criterion to classify viruses?

A) morphology
B) size
C) number of capsomeres
D) biochemical tests
E) nucleic acid

Answer 3

D

Question 4

Continuous cell lines differ from primary cell lines in that

A) continuous cell lines always have to be re-isolated from animal tissues.
B) continuous cell lines are derived from primary cell lines.
C) viruses can be grown in continuous cell lines.
D) continuous cell lines are from human embryos.
E) continuous cell lines can be maintained through an indefinite number of generations.

Question 5

A clear area against a confluent ʺlawnʺ of bacteria is called a

A) cell lysis.
B) rash.
C) plaque.
D) pock.
E) phage.

Question 6

A persistent infection is one in which

A) the virus remains in equilibrium with the host without causing a disease.
B) host cells are transformed.
C) host cells are gradually lysed.
D) the disease process occurs gradually over a long period.
E) viral replication is unusually slow.

Question 7

Lysogeny can result in all of the following EXCEPT

A) acquisition of new characteristics by the host cell.
B) phage conversion.
C) specialized transduction.
D) immunity to reinfection by any phage.
E) immunity to reinfection by the same phage.

Question 8

Which of the following is NOT utilized to culture viruses?

A) animal cell cultures
B) culture media
C) embryonated eggs
D) laboratory animals
E) bacterial cultures

Question 9

A viroid is a(n)

A) provirus.
B) infectious protein.
C) capsid without nucleic acid.
D) complete, infectious virus particle.
E) infectious piece of RNA without a capsid.

Question 10

An infectious protein is a

A) bacteriophage.
B) prion.
C) papovavirus.
D) viroid.
E) retrovirus.

Question 11

Which of the following would be the first step in biosynthesis of a virus with a - (minus) strand of RNA?

A) transcription of mRNA from DNA
B) synthesis of double-stranded RNA from a DNA template
C) synthesis of DNA from an RNA template
D) synthesis of double-stranded RNA from an RNA template
E) synthesis of DNA from a DNA template

Question 12

Which of the following statements provides the most significant support for the idea that viruses are nonliving chemicals?

A) They are chemically simple.
B) They are filterable.
C) They cause diseases similar to those caused by chemicals.
D) They cannot reproduce themselves outside a host.
E) They are not composed of cells.

Question 13

Which of the following statements is NOT true of lysogeny?

A) It can give infected pathogens the genetic information for toxin production.
B) It is a ʺsilentʺ infection; the virus does not replicate.
C) Lytic cycle may follow lysogeny.
D) Prophage is inserted into the host genome.
E) It causes lysis of host cells.

Question 14

The definition of lysogeny is

A) the period during replication when virions are not present.
B) when the burst time takes an unusually long time.
C) attachment of a phage to a cell.
D) lysis of the host cell due to a phage.
E) phage DNA is incorporated into host cell DNA.

Question 15

Bacteriophages and animal viruses do NOT differ significantly in which one of the following steps?

A) attachment
B) uncoating
C) biosynthesis
D) penetration
E) release

Question 16

Which of the following statements is FALSE?

A) A prophage is phage DNA inserted into a bacterial chromosome.
B) A prophage may result in new properties of the host cell.
C) Prophage genes are repressed by a repressor protein coded for by the prophage.
D) A prophage can ʺpopʺ out of the chromosome.
E) The prophage makes the host cell immune to infection by other phages.

Question 17

Figure 13.1

The structures illustrated in Figure 13.1 are composed of

A) DNA or RNA.
B) RNA.
C) viroids.
D) Capsomeres.
E) DNA.

Question 18

An envelope is acquired during which of the following steps?

A) penetration
B) adsorption
C) release
D) biosynthesis
E) uncoating

Question 19

How do all viruses differ from bacteria?

A) Viruses are not composed of cells.
B) Viruses are filterable.
C) Viruses are obligate intracellular parasites.
D) Viruses do not have any nucleic acid.
E) Viruses do not reproduce.

Question 20

Figure 13.1

In Figure 13.1, which structure is a complex virus?

A) a
B) b
C) c
D) d
E) All of the structures are complex viruses.

Question 21

Oncogenic viruses

A) have no effect on the host cell.
B) cause acute infections.
C) are genetically unstable.
D) cause tumors to develop.
E) are lytic viruses that kill the host cell.

Question 22

DNA made from an RNA template will be incorporated into the virus capsid of

A) Hepadnaviridae.
B) influenzavirus.
C) bacteriophage families.
D) Herpesviridae.
E) Retroviridae.

Question 23

Bacteriophages derive all of the following from the host cell EXCEPT

A) tRNA.
B) lysozyme.
C) nucleotides.
D) amino acids.
E) ATP.

Question 24

A viral species is a group of viruses that

A) has the same genetic information and ecological niche.
B) has the same morphology and nucleic acid.
C) infects the same cells and cause the same disease.
D) cannot be defined.

Question 25

Which of the following statements about viruses is FALSE?

A) Viruses contain DNA or RNA but never both.
B) Viruses contain a protein coat.
C) Viruses have genes.
D) Viruses use their own catabolic enzymes.
E) Viruses use the anabolic machinery of the cell.

Question 26

A virusʹs ability to infect an animal cell depends primarily upon the

A) presence of pili on the host cell wall.
B) enzymatic activity of a host cell.
C) host cellʹs ability to phagocytize viral particles.
D) presence of receptor sites on the cell membrane.
E) type of viral nucleic acid.

Question 27

Figure 13.2

Assume a patient had chickenpox (human herpesvirus 3) as a child. Which line on the graph in Figure 13.2 would show the number of viruses present in this person as a 60 -year-old with shingles (human herpesvirus 3)?

A) a
B) b
C) c
D) d
E) e

Question 28

Generally, in an infection caused by a DNA-containing virus, the host animal cell supplies all of the following EXCEPT

A) nucleotides.
B) DNA polymerase.
C) RNA polymerase.
D) tRNA.
E) None of the answers are correct; all of these are supplied by the host animal cell.

Question 29

The following steps occur during multiplication of retroviruses. Which is the fourth step?

A) penetration
B) uncoating
C) attachment
D) synthesis of double-stranded DNA
E) synthesis of +RNA

Question 30

Bacteriophage replication differs from animal virus replication because only bacteriophage replication involves

A) assembly of viral components.
B) replication of viral nucleic acid.
C) adsorption to specific receptors.
D) injection of naked nucleic acid into the host cell.
E) lysis of the host cell.

Question 31

Figure 13.2

Assume a patient has influenza. During which time on the graph in Figure 13.2 would the patient show the symptoms of the illness?

A) a
B) b
C) c
D) d
E) e

Question 32

Viruses that utilize reverse transcriptase belong to the virus families

A) Rhabdoviridae and Herpesviridae.
B) Herpesviridae and Retroviridae.
C) Hepadnaviridae and Retroviridae.
D) Retroviridae and Picornaviridae.
E) Herpesviridae and Poxviridae.

Question 33

An example of a latent viral infection is

A) cold sores.
B) mumps.
C) subacute sclerosing panencephalitis.
D) smallpox.
E) influenza.

Question 34

The most conclusive evidence that viruses cause cancers is provided by

A) finding oncogenes in viruses.
B) some liver cancer patients having had hepatitis.
C) cancer following injection of cell-free filtrates.
D) the presence of antibodies against viruses in cancer patients.
E) treating cancer with antibodies.

Question 35

Assume you have isolated an unknown virus. This virus has a single, positive sense strand of RNA, and possesses an envelope. To which group does it most likely belong?

A) togavirus
B) retrovirus
C) picornavirus
D) herpesvirus
E) papovavirus

Question 36

A lytic virus has infected a patient. Which of the following would best describe what is happening inside the patient?

A) The virus is infecting cells and then releasing only small amounts of virus.
B) The virus is incorporating its nucleic acid with that of the patientʹs cells.
C) The virus is slowly killing the patientʹs cells.
D) The virus is causing the death of the infected cells in the patient.
E) The virus is not killing any cells in the host.

Question 37

Which of the following places these items in the correct order for DNA-virus replication? 1. Maturation
2) DNA synthesis
3) Transcription
4) Translation

A) 2; 3; 4; 1
B) 4; 3; 2; 1
C) 3; 4; 1; 2
D) 4; 1; 2; 3
E) 1; 2; 3; 4

Question 38

Some viruses, such as human herpesvirus 1, infect a cell without causing symptoms. These are called

A) latent viruses.
B) lytic viruses.
C) slow viruses.
D) phages.
E) unconventional viruses.

Question 39

The following steps occur during multiplication of herpesviruses. Which is the third step?

A) penetration
B) attachment
C) biosynthesis
D) release
E) uncoating

Question 40

The mechanism whereby an enveloped virus leaves a host cell is called

A) budding.
B) transduction.
C) penetration.
D) abduction.
E) lysogeny.

Question 41

Dogs do not get measles because their cells lack the correct receptor sites for that virus.

Question 42

Positive sense RNA strands of viruses are treated like mRNA inside the host cell.

Question 43

A viroid is a completely developed infectious agent composed of nucleic acid and surrounded by a capsid.

Question 44

The following steps occur during biosynthesis of a + strand RNA virus. What is the third step?

A) synthesis of viral proteins
B) synthesis of + strand RNA
C) penetration and uncoating
D) synthesis of - strand RNA
E) attachment

Question 45

Bacteriophages are used as vectors in genetic engineering to insert new genes into bacteria. Describe the process that makes this genetic recombination possible.

Question 46

A segmented genome can result in antigenic shift.

Question 47

Viruses are the only known infectious agents that are obligatory intracellular parasites.

Question 48

Explain the steps involved in bacteriophage DNA entering a bacterial cell.

Question 49

Discuss why viruses are considered infectious ʺparticlesʺ on the borderline between living and non-living.

Question 50

Glycoprotein spikes are found on the capsids of all viruses.

Question 51

Which one of the following steps does NOT occur during multiplication of a picornavirus?

A) synthesis of DNA
B) synthesis of - strands of RNA
C) synthesis of viral proteins
D) synthesis of + strands of RNA
E) None of the answers is correct.

Question 52

What contributes to antigenic shift in influenza viruses?

A) ease of virus transmission
B) attachment spikes
C) worldwide distribution of the virus
D) a segmented genome
E) different virus subtypes

Question 53

Which of the following is most likely a product of an early gene?

A) envelope proteins
B) spike proteins
C) capsid proteins
D) DNA polymerase
E) lysozyme

Question 54

The basic mechanism of viral multiplication is similar for all viruses.

Question 55

Binomial nomenclature is used to name viruses.

Question 56

were first identified in cancer-causing viruses and can induce in infected cells.

A) Oncogenes; transformation
B) Segmented genomes; reassortment
C) T antigens; lysis
D) Glycoprotein spikes; syncytia formation
E) Herpes viruses; lesions

Question 57

Most RNA viruses carry which of the following enzymes?

A) reverse transcriptase
B) lysozyme
C) ATP synthase
D) RNA-dependent RNA polymerase
E) DNA-dependent DNA polymerase

Question 58

Most drugs that interfere with viral multiplication also interfere with host cell function.

Question 59

Helical and icosahedral are terms used to describe the shapes of a virus envelope.

Question 60

Compare and contrast the lytic cycle of infection of a DNA virus and an RNA virus.

Question 61

How is the replication of the viral genome of retroviruses unique among the viruses?

Question 62

Researchers studying tissues of diseased marine mammals have identified what appear to be viral particles by electron microscopy. Describe three methods you might use to attempt to culture this virus for further study.