Deck 13: Characterizing and Classifying Viruses, Viroids, and Prions

Question 1

Host specificity of a virus is due to

A) the presence of an envelope.
B) the presence or absence of a cell wall on the host cell.
C) interactions between viral and cellular surface molecules.
D) particular genes that it shares with the infected cell.
E) differences in size between the virus and the host cell.

Answer 1

C

Question 2

Tobacco mosaic virus was first isolated and characterized by

A) Iwanowski.
B) Stanley.
C) Lacks.
D) Rous.
E) Prusiner.

Answer 2

B

Question 3

All of the following statements are true of lambda phage EXCEPT:

A) It can be present as a provirus.
B) It has a lytic phase.
C) It has a double- stranded DNA genome.
D) It is a temperate phage.
E) It is a lysogenic phage.

Answer 3

A

Question 4

Which of the following types of viruses have no extracellular state?

A) animal viruses
B) fungal viruses
C) bacterial viruses
D) plant viruses
E) All of these have an extracellular state.

Question 5

Which of the following have been the least characterized?

A) plant viruses
B) All of these are well characterized.
C) animal viruses
D) bacterial viruses
E) fungal viruses

Question 6

Which of the following would NOT be found as a subcomponent of a bacteriophage?

A) tail fibers
B) envelope
C) icosahedral capsid
D) base plate
E) DNA

Question 7

All of the following statements concerning viruses are true EXCEPT:

A) Viral capsids can assume one of three basic shapes.
B) Tobacco mosaic virus was the first virus to be discovered and characterized.
C) Viruses enter a cell to complete the replication they have begun extracellularly.
D) Some viruses have an outer membrane called an envelope.
E) Viruses never contain both DNA and RNA.

Question 8

Why is lysogeny advantageous to a bacteriophage?

A) The genetic material of the phage can be passed on to future generations of cells.
B) It allows the bacteriophage to infect cells it would not normally infect.
C) It enables the bacteriophage to take over the cell.
D) It allows the bacteriophage to destroy the host cell's DNA.
E) It speeds up the viral life cycle.

Question 9

Which of the following is an enzyme necessary for the successful replication of bacteriophage T4?

A) lysozyme
B) matrix proteins
C) reverse transcriptase
D) RNA- dependent RNA transcriptase
E) capsomere

Question 10

Put the following stages of a lytic replication cycle in order, from earliest to latest stages:
I) Synthesis
II) Assembly
III) Attachment
IV) Release
V) Entry

A) I, III, V, II, IV
B) V, III, II, IV, I
C) I, II, III, V, IV
D) III, V, I, II, IV
E) III, II, V, I, IV

Question 11

The broadest classification currently used for all viruses is the

A) genus.
B) order.
C) class.
D) phylum.
E) family.

Question 12

Which of the following agents is capable of inducing conversion of a prophage back to a lytic phage?

A) X rays
B) UV light
C) presence of +ssRNA
D) Both A and B are correct.
E) A, B, and C are correct.

Question 13

The outermost layer of a virion fulfills which of the following functions of the virus?

A) recognition
B) protection
C) replication
D) Both A and B are correct.
E) A, B, and C are correct.

Question 14

Which of the following is associated with the attachment of a bacteriophage to a bacterial cell?

A) receptor specificity
B) random collisions
C) chemical attractions
D) Both B and C are correct.
E) A, B, and C are correct.

Question 15

The phenomenon of transduction is associated with which stage of a bacteriophage life cycle?

A) synthesis
B) attachment
C) release
D) entry
E) assembly

Question 16

Which of the following is another term for a lysogenic phage?

A) enveloped virus
B) retrovirus
C) bacteriophage
D) temperate phage
E) nucleocapsid

Question 17

All of the following statements concerning virus taxonomy are true EXCEPT:

A) Currently there are only three orders of viruses.
B) Staining is used as a means of classifying viruses.
C) Virus family names are sometimes derived from the name of an important virus within the family.
D) The ICTV establishes proper taxonomic schemes for virus classification.
E) Families are the highest taxonomic groups used for all viruses.

Question 18

During the intracellular state, a virus exists solely as a

A) nucleic acid.
B) protein.
C) lipid.
D) Both B and C are correct.
E) Both A and C are correct.

Question 19

The process of excising a prophage from the host chromosome, in order to reenter the lytic phase, is called

A) exocytosis.
B) induction.
C) lysogeny.
D) transduction.
E) metastasis.

Question 20

Viruses are primarily classified according to their

A) shape.
B) size.
C) type of nucleic acid.
D) number of chromosomes.
E) type of life cycle.

Question 21

Prusiner was the first to describe which of the following?

A) HIV
B) prions
C) temperate phages
D) tobacco mosaic virus
E) retroviruses

Question 22

The genome of which of the following types of animal virus can act directly as mRNA?

A) ssDNA viruses
B) retroviruses
C) dsRNA viruses
D) +ssRNA viruses
E) - ssRNA viruses

Question 23

The largest viruses are about the size of the smallest eukaryotic cell.

Question 24

Plaque assays are used for

A) the cultivation of viruses that cannot be grown any other way.
B) the study of prions.
C) estimation of the number of phages in a culture.
D) evaluation of the cancer- causing ability of a virus.
E) counting the number of latent phages in a cell.

Question 25

Tumors invade other organs and tissues in a process called

A) budding.
B) a plaque assay.
C) metastasis.
D) neoplasia.
E) latency.

Question 26

Viroids infect

A) fungi.
B) bacteria.
C) all organisms.
D) plants and animals.
E) plants.

Question 27

Diploid cell cultures and continuous cell cultures differ in which of the following ways?

A) source of cells
B) longevity
C) convenience of use
D) Both A and B are correct.
E) Both A and C are correct.

Question 28

Viruses known to cause only a limited number of human cancers.

Question 29

How are prions different from all other known infectious agents?

A) They act as slow viruses.
B) They can be destroyed by incineration.
C) They lack nucleic acid.
D) They cannot reproduce outside a cell.
E) They cause neurological problems.

Question 30

How is the HIV provirus different from a lambda phage prophage?

A) All the offspring of a cell infected with a prophage will contain the virus.
B) The HIV provirus is integrated permanently into the host cell's DNA.
C) All subsequent generations of HIV- infected cells carry the prophage.
D) Lambda phage- infected cells produce virus slowly over time.
E) The HIV provirus is inactive inside the host cell.

Question 31

All of the following are diseases known to be caused by prions EXCEPT:

A) Creutzfeldt- Jakob disease.
B) Alzheimer's disease.
C) kuru.
D) bovine spongiform encephalopathy.
E) scrapie.

Question 32

Which of the following types of animal virus requires RNA- dependent RNA transcriptase to be replicated?

A) +ssRNA viruses
B) - ssRNA viruses
C) dsDNA viruses
D) ssDNA viruses
E) retroviruses

Question 33

Which of the following membranes can give rise to a viral envelope?

A) the cytoplasmic membrane
B) the endoplasmic reticulum
C) the nuclear membrane
D) Both A and B are correct.
E) A, B, and C are correct.

Question 34

Most viruses cannot be seen by light microscopy.

Question 35

The viral genome codes for all the proteins in the viral envelope.

Question 36

Reverse transcriptase is associated with which of the following?

A) retroviruses
B) dsDNA viruses
C) dsRNA viruses
D) +ssRNA viruses
E) - ssRNA viruses

Question 37

Although they are cheaper to culture than animal viruses, bacteriophages are more difficult to culture.

Question 38

What is the role of protooncogenes in theories of how viruses cause cancer?

A) They prevent the immune system from attacking cancer- causing viruses.
B) They cause cancer viruses to replicate faster.
C) They play a role in the control of cell division.
D) They make cells more susceptible to infection by cancer- causing viruses.
E) They prevent cancer- causing viruses from leaving the cell.

Question 39

The majority of cases of infant diarrhea are caused by what kind of virus?

A) retroviruses
B) dsRNA viruses
C) +ssRNA viruses
D) - ssRNA viruses
E) dsDNA viruses

Question 40

All of the following statements are true for animal viruses and bacteriophage EXCEPT:

A) Animal viruses take longer to replicate than bacteriophage.
B) Animal viruses can enter via direct penetration.
C) The attachment for bacteriophage and animal viruses is dependent upon chemical attraction.
D) Uncoating is required for bacteriophage.
E) The bacteriophage genome can incorporate into the host chromosome.

Question 41

Transcription of RNA from RNA does not occur in cells.

Question 42

The presence of lysogenic phages can change a harmless bacterium into a pathogen via a process known as
.

Question 43

Bacteriophages are released quickly and in large quantities from an infected cell.

Question 44

The combination of a virus's protein coat and nucleic acid core is called the .

Question 45

An icosahedron is a type of capsid.

Question 46

Poxvirus is assembled in the cytoplasm of the cell instead of in the nucleus, as most dsDNA viruses are.

Question 47

are composed of a single protein called PrP.

Question 48

Virus vaccines are always cultured in embryonated chicken eggs.

Question 49

HeLa cells are a famous type of cell culture.

Question 50

RNA is viral single- stranded RNA that can act directly as mRNA.

Question 51

Viral capsids are composed of subunits called _ .

Question 52

A(n) _ is a clear zone on a bacterial lawn where cells have been killed by the activity of a bacteriophage.

Question 53

is the process of viral capsid removal within the infected cell.

Question 54

An animal virus that does not have an envelope is described as a(n) virus.

Question 55

For a lytic bacteriophage, the time from attachment to release is known as the .

Question 56

, genes that play a role in proper cell division, may also play a role in some types of cancer.

Question 57

Infections in which viruses are shed slowly and steadily from host cells are called infections.

Question 58

Assembly of new viruses is a process that usually requires a variety of viral and cellular enzymes to direct it.

Question 59

is uncontrolled cell division in a multicellular animal.

Question 60

Bacteriophages use the enzyme to breach the bacterial cell wall.

Question 61

Describe the mechanism by which PrP is infectious.

Question 62

Describe the difference between lysogeny and latency.

Question 63

Compare and contrast the ways in which animal, plant, and bacterial viruses gain entry into their host cells.

Question 64

Why do only some viruses cause cancer?

Question 65

Why is the synthesis of mRNA a central issue for all viruses? How do different types of viruses achieve this goal?