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

Question 1

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

A) protection
B) recognition
C) replication
D) protection and recognition
E) recognition and replication

Answer 1

D

Question 2

Host specificity of a virus is due to

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

Answer 2

E

Question 3

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

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

Answer 3

A

Question 4

Who was the first person to demonstrate the existence of viruses?

A) Stanley
B) Rous
C) Lacks
D) Ivanowsky
E) Prusiner

Question 5

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

A) UV light
B) X rays
C) presence of +ssRNA
D) UV light and X rays
E) UV light and +ssRNA

Question 6

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

Question 7

Which of the following statements concerning viruses is FALSE?

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

Question 8

Viruses are primarily classified according to their

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

Question 9

Which of the following statements regarding virus taxonomy is true?

A) Viruses are classified on the basis of the taxonomy of their host organisms.
B) Virus classes are well established.
C) Some virus family names are derived from the name of an important member of the family.
D) The species epithet is a latin descriptor of the virion structure.
E) Virus classes are based on the domain of the host organism.

Question 10

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

A) random collisions
B) chemical attractions
C) receptor specificity
D) chemical attractions and receptor specificity
E) random collisions, chemical attractions, and receptor specificity

Question 11

Why is lysogeny advantageous to a bacteriophage?

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

Question 12

The phenomenon of transduction is associated with which of the stages of a bacteriophage infection cycle?

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

Question 13

Which of the following infectious particles do not have protein in their structure?

A) bacteriophages
B) prions
C) animal viruses
D) viroids
E) both prions and viroids

Question 14

How are fungal viruses different from viruses that infect other organisms?

A) they have no extracellular state.
B) they have only DNA for genetic material.
C) they have no capsid.
D) they have no intracellular state.
E) they cannot pass through a filter.

Question 15

Zones of clearing in cell cultures that are the result of virus infection are called plaques. Sometimes "cloudy plaques" are seen on bacterial cultures infected with bacteriophage. What type of viral infection might cause this appearance?

A) lytic
B) lysogenic
C) prion
D) viroid
E) transducing

Question 16

Which of the following is matched incorrectly?

A) poliovirus - direct penetration
B) herpesvirus - endocytosis
C) adenovirus - membrane fusion
D) measles virus - membrane fusion
E) HIV - membrane fusion

Question 17

Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but not in the lysogenic cycle?

A) attachment
B) entry
C) digestion of host DNA
D) viral protein synthesis
E) both digestion of host DNA and viral proteins synthesis

Question 18

Which of the following statements comparing virus classification and taxonomy of organisms is true?

A) Both viruses and organisms are organized into classes.
B) The common names of viruses are their genus and species epithet, as they are with organisms.
C) Both viruses and organisms are organized into domains.
D) Genus and specific epithet are used in both classification systems.
E) Only families are common to both viral classification and organism taxonomy.

Question 19

The enzyme lysozyme is critical for which of the stages of a bacteriophage T4 infection cycle?

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

Question 20

During the intracellular state, a virus exists as

A) a lipid.
B) a protein.
C) a nucleic acid.
D) both a protein and a nucleic acid.
E) both a lipid and a nucleic acid.

Question 21

Plaque assays are used for

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

Question 22

Double-stranded DNA genomes are found

A) only in viroids.
B) only in cells.
C) only in viruses.
D) in both cells and viruses.
E) in both viruses and viroids.

Question 23

Proteins are present in

A) cells only.
B) viruses only.
C) viroids only.
D) both cells and viruses.
E) cells, viruses, and viroids.

Question 24

How are prions different from all other known infectious agents?

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

Question 25

Cytoplasm is a characteristic of

A) cells only.
B) viruses only.
C) both cells and viruses.
D) viroids only.
E) both viroids and viruses.

Question 26

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

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

Question 27

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

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

Question 28

A lipid membrane is present

A) only in viruses.
B) in both cells and viruses.
C) only in cells.
D) only in prions.
E) in both prions and viroids.

Question 29

Double-stranded RNA genomes can be found

A) only in cells.
B) in both cells and viruses.
C) only in viruses.
D) in prions.
E) in both prions and viruses.

Question 30

Reverse transcriptase is associated with which of the following?

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

Question 31

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

A) longevity
B) source of cells
C) convenience of use
D) longevity and convenience of use
E) longevity and source of cells

Question 32

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

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

Question 33

One mechanism by which viruses may cause cancer is to interrupt the genetic regulatory sequences of repressor proteins. Which of the following types of viruses is most likely to be involved in causing cancer by this mechanism?

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

Question 34

The infectious particles of fungi have RNA genomes and lack a capsid. They are therefore similar to

A) bacteriophages.
B) enveloped viruses.
C) prions.
D) viroids.
E) lysogens.

Question 35

Which of the following individuals discovered prions?

A) Lacks
B) Iwanowsky
C) Prusiner
D) Stanley
E) Rous

Question 36

Viroids infect

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

Question 37

Tumors invade other organs and tissues in a process called

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

Question 38

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

A) the nuclear membrane
B) the cytoplasmic membrane
C) the endoplasmic reticulum
D) the nuclear and cytoplasmic membranes
E) the nuclear and cytoplasmic membranes and the endoplasmic reticulum

Question 39

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

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

Question 40

In contrast to most dsDNA animal viruses, the poxviruses replicate solely in the cytoplasm of the host cell. This fact implies that the viral genome may encode

A) reverse transcriptase.
B) a DNA polymerase.
C) RNA-dependent RNA transcriptase.
D) ribosome components.
E) reverse transcriptase and RNA-dependent RNA transcriptase.

Question 41

Many diseases of plants are caused by infectious RNA molecules lacking capsids.

Question 42

During __________, viruses remain dormant in a cell.

A) budding
B) latency
C) lytic replication
D) persistent infection
E) oncogenesis

Question 43

Poxvirus is assembled in the cytoplasm of the cell instead of in the nucleus, as is the case for the majority of dsDNA viruses.

Question 44

Virus infection results in cancer in the process of

A) lytic replication.
B) budding.
C) oncogenesis.
D) persistent infection.
E) latency.

Question 45

Viral capsids are composed of subunits called __________.

Question 46

Assembly of new viruses is a process that usually requires the direction of a variety of viral and cellular enzymes.

Question 47

Virus replication results in the death of the cell in a(n) __________ infection.

A) lytic
B) latent
C) persistent
D) oncogenic
E) both latent and persistent

Question 48

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

Question 49

Protozoa are susceptible to viral attack.

Question 50

Bacteriophages are cheaper and easier to culture than animal viruses.

Question 51

Viruses cause most human cancers.

Question 52

Viruses are shed slowly and steadily during

A) lytic replication.
B) budding.
C) oncogenesis.
D) persistent infection.
E) latency.

Question 53

Virus vaccines are always cultured in embryonated chicken eggs.

Question 54

The number of new bacteriophages released from each infected cell is called the __________ size.

Question 55

Transcription of RNA from RNA does not occur in uninfected cells.

Question 56

is a mechanism of release for enveloped viruses.

A) Lytic replication
B) Persistent infection
C) Oncogenesis
D) Latency
E) Budding

Question 57

Bacteriophage release is a gradual process in which small numbers are released at a time.

Question 58

A(n) __________ is a 20-sided polyhedral capsid.

Question 59

Most viruses cannot be seen by light microscopy.

Question 60

Bacteriophages use the enzyme __________ to breach the bacterial cell wall.

Question 61

RNA viruses such as HIV require the activity of reverse __________ to become proviruses.

Question 62

Prions are composed of a single protein called __________. (Be sure you use proper capitalization.)

Question 63

The process in which viral capsids are removed within the infected cell is called __________.

Question 64

In enveloped viruses, virus-encoded __________ proteins are required for the assembly of the envelope around the capsid.

Question 65

Genes that play a role in proper cell division but may also play a role in some types of cancer are called __________.

Question 66

Describe the difference between lysogeny and latency.

Question 67

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

Question 68

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

Question 69

Three __________ represent the highest level of taxonomic rank used in classifying viruses.

Question 70

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

Question 71

A scientist discovers a new virus associated with a cancer. She is able to culture it in the laboratory and characterize it. The virions contain an RNA genome and enzymes with reverse transcriptase activity. What do these observations suggest about the classification of the new virus? What does this suggest regarding a mechanism for causing cancer?

Question 72

Describe the mechanism by which PrP is infectious.

Question 73

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

Question 74

Another term for a lysogenic phage is a __________ phage.

Question 75

Virus RNA that can act directly as mRNA is __________-strand RNA.