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

Question 1

Which of the following is involved in the attachment of a bacteriophage to a bacterial cell?

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

Answer 1

E

Question 2

The shape of a virion is a function of the of the virus.

A) capsid
B) cell type of the host cell
C) envelope
D) type of genome material
E) size of the genome material

Answer 2

A

Question 3

What is the correct order for the stages of a lytic replication cycle, from earliest to latest stages?

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

Answer 3

B

Question 4

The envelope portion of an enveloped virus is composed of

A) virus-encoded glycoproteins.
B) host cell membranes containing virus-encoded glycoproteins.
C) glycolipids of the host cell.
D) phospholipids from host cell membranes.
E) host glycolipids and virus-encoded glycoproteins.

Question 5

Classification of viruses includes

A) orders.
B) classes.
C) families.
D) orders and families.
E) classes, orders, and families.

Question 6

Why is lysogeny advantageous to a bacteriophage?

A) It enables the bacteriophage to take over the cell.
B) It allows the bacteriophage to destroy the host cellʹs DNA.
C) It speeds up the viral infection cycle.
D) It allows the bacteriophage to infect cells it would not normally infect.
E) The genetic material of the bacteriophage is amplified many times over that seen in a lytic phage.

Question 7

Which of the following statements regarding virus taxonomy is TRUE?

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

Question 8

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

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

Question 9

Which virus is CORRECTLY matched with its method of entry?

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

Question 10

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

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

Question 11

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

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

Question 12

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

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

Question 13

A is a virus that infects bacterial cells.

A) viroid
B) nucleocapsid
C) virion
D) prion
E) bacteriophage

Question 14

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

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

Question 15

Naked capsid animal viruses gain entry to host cells by

A) membrane fusion.
B) endocytosis.
C) direct penetration.
D) both endocytosis and direct penetration.
E) endocytosis, direct penetration, and membrane fusion.

Question 16

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

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

Question 17

Host specificity of a virus is due to

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

Question 18

Which of the following may occur in a lysogenic infection, but NOT a latent one?

A) The viral DNA integrates (inserts) into the host cell DNA.
B) The prophage/provirus is replicated with the host DNA.
C) The prophage/provirus alters gene expression in the host cell.
D) The provirus/prophage directs the synthesis of viral proteins.
E) The inserted viral DNA may leave the host DNA.

Question 19

Which of the following is present in cells only during virus infection?

A) DNA-RNA heteroduplex
B) ssRNA
C) ssDNA
D) dsDNA
E) triplet RNA

Question 20

Which of the following is an accurate description of a virion?

A) the nucleic acid of a viral pathogen inside a host cell
B) the protein portion of a viral particle
C) the nucleic acid of a viral pathogen
D) a population of infectious particles
E) an infectious particle of protein and nucleic acid outside a host cell

Question 21

The development of a cancerous cell is said to require ʺmultiple hits.ʺ This means

A) multiple cell cycle regulators are inactivated at once.
B) multiple oncogenic viruses infect the cell at the same time.
C) a series of separate events over time lead to the loss of cell cycle regulation.
D) the cell must be infected with several different types of viruses to be transformed.
E) several protoncogenes are activated at the same time.

Question 22

A cell is infected with a virus carrying an oncogene sequence in its genome. What process may occur if the oncogene is expressed in the infected cell?

A) latency
B) lysis
C) neoplasia
D) lysogeny
E) both lysis and neoplasia

Question 23

Why are diploid cell cultures preferred over continuous cell cultures?

A) Diploid cells have undergone changes in their chromosome structure that make them more stable.
B) Diploid cells are more nearly like cells of whole organisms than continuous culture cells.
C) Continuous cell cultures are expensive to maintain.
D) Results from continuous culture cells do not apply to disease in whole organisms.
E) Diploid cells last far longer than continuous culture cells.

Question 24

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

Question 25

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

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

Question 26

The process of metastasis results from

A) oncogene expression.
B) neoplasia.
C) viral latency.
D) benign tumors.
E) malignant tumors.

Question 27

Which of the following is a feature shared by viruses and living organisms?

A) the ability to increase in size
B) metabolic capability
C) possession of a genome that directs synthesis of materials necessary for replication
D) presence of cytoplasm
E) responsiveness

Question 28

How are prions different from all other known infectious agents?

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

Question 29

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

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

Question 30

Infection with is likely to result in destruction of the host cell by lysis.

A) oncogenic viruses
B) enveloped viruses
C) naked viruses
D) viroids
E) prions

Question 31

Some human viruses are difficult to study because

A) they only grow in normal human cells.
B) very few laboratories have the skills to culture the viruses.
C) the growth medium for the host cells is complex.
D) they grow very slowly.
E) they establish latent infections and cannot be induced.

Question 32

Small circular RNA molecules without capsids are characteristic of

A) viroids.
B) viruses.
C) plasmids.
D) prions.
E) viruses and prions.

Question 33

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

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

Question 34

What is one of the most difficult aspects of studying animal viruses?

A) The viruses are hard to obtain.
B) The use of animals is expensive, and unethical to many people.
C) The viruses are extremely dangerous to handle.
D) The study requires expensive facilities.
E) The use of animals to study the viruses is unethical in the eyes of many.

Question 35

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) All subsequent generations of HIV-infected cells carry the provirus.
C) The HIV provirus is integrated permanently into the host cellʹs DNA.
D) The HIV provirus is inactive inside the host cell.
E) Lambda phage-infected cells produce virus slowly over time.

Question 36

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

A) dsRNA viruses
B) -ssRNA viruses
B) ssDNA viruses
C) +ssRNA viruses

Question 37

Retroviruses require the activity of to complete their infection cycle.

A) reverse transcriptase
B) lysozyme
C) viral RNA polymerase
D) RNA-dependent RNA transcriptase
E) RNA-dependent RNA polymerase

Question 38

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 longevity and convenience of use
E) both longevity and source of cells

Question 39

Plaque assays are used for

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

Question 40

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) dsRNA viruses

A) retroviruses
B) -ssRNA viruses
B) both +ssRNA and -ssRNA viruses
C) +ssRNA viruses

Question 41

The combination of a virusʹs protein coat and nucleic acid core is called the (capsid/virion/nucleocapsid).

Question 42

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

Question 43

Assembly of enveloped viruses requires (membrane/matrix/receptor) to bring together the nucleocapsid and the envelope.

Question 44

Some viruses can be cultured on (continuous/diploid/animal) cells which are descended from neoplastic cells.

Question 45

Viruses cause most human cancers.

Question 46

The first virus isolated, Tobacco mosaic virus, has a (complex/helical/polyhedral) capsid morphology, which facilitated its isolation.

Question 47

Bovine spongiform encephalopathy is an example of a prion disease.

Question 48

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

Question 49

Prions cause disease in

A) bacteria.
B) mammals.
C) fungi.
D) birds.
E) plants.

Question 50

All members of a virus family have the same type of genome structure.

Question 51

A is a mass of neoplastic cells.

A) tumor
B) plaque
C) metastasis
D) diploid culture
E) gall

Question 52

The process known as is a mechanism of release for enveloped viruses.

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

Question 53

During , viral synthesis is suspended.

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

Question 54

All viruses use the host cellʹs nucleic acid polymerases for replication.

Question 55

Protozoa are susceptible to viral attack.

Question 56

Virus replication results in the death of the cell in infection(s).

A) a latent
B) a lytic
C) a lysogenic
D) a persistent
E) both latent and persistent

Question 57

The virions shown in the figure have a (polyhedral/helical/complex) capsid.

Question 58

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

Question 59

Virus entry requires the presence of specific cell structures.

Question 60

Fertilized chicken eggs are used to culture some vaccine strains.

Question 61

Uncontrolled cell division in animals is known as (metastasis/neoplasia/cancer).

Question 62

Three (orders/families/classes) represent the highest level of taxonomic rank used in classifying viruses.

Question 63

A scientist discovers a new virus associated with a cancer. She is able to culture it in the laboratory and begins to analyze it. What features will help her determine the virusʹ classification? How does this help her understand the virusʹ mechanism for causing cancer?

Question 64

The process in which viral capsids are removed within the infected cell is called (entry/disassembly/uncoating).

Question 65

Viruses are responsible for (all/most/some) human cancers. (Use relative terms not numbers.)

Question 66

Describe the mechanism by which PrP is infectious.

Question 67

Describe the difference between lysogeny and latency.

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

RNA dependent RNA polymerase is required for successful infection by (+ssRNA/-ssRNA/dsRNA) viruses.

Question 70

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

Question 71

The graph in the figure shows a pattern of virion abundance consistent with a (lytic/latent/persistent) virus infection cycle.

Question 72

Genes that play a role in proper cell division but may also play a role in some types of cancer are called (oncogenes/protooncogenes/promoters).

Question 73

Another term for a lysogenic phage is a (temperate/latent/prophage) phage.

Question 74

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

Question 75

An animal virus that does not have an envelope is described as a(n) (naked/unenveloped/capsid) virion.