Deck 6: Viruses

Question 1

__________ gained notoriety when they were implicated in brain infections, such as what is popularly known as mad cow disease.

A) Viroids
B) Viruses
C) Prions
D) Bacteria
E) Virions

Answer 1

C

Question 2

__________ phages have been used to nucleate the growth of crystalline "nanowires" for electronic devices.

A) Icosahedral
B) Complex
C) Asymmetrical
D) Filamentous
E) Viroid

Answer 2

D

Question 3

In bacteriophage T4, the DNA genome is contained in the head, and binding to the host is facilitated by attachment of the:

A) capsid
B) neck
C) tail fibers
D) envelope
E) tegument

Answer 3

C

Question 4

Virus particles can be observed by standard transmission electron microscopy (TEM), but details of capsid structure require visualization by:

A) phase-contrast microscopy
B) scanning electron microscopy
C) cryo-electron microscopy
D) negative stain
E) bright field microscopy

Question 5

Some viral species may derive their __________ from intracellular membranes, such as the nuclear membrane or endoplasmic reticulum.

A) capsid
B) genome
C) envelope
D) neck
E) tail fibers

Question 6

__________ diseases are unique in that they can be transmitted by an infective protein that propagates conformational change of existing molecules without synthesizing entirely new infective molecules.

A) Viral
B) Viroid
C) Bacterial
D) Virion
E) Prion

Question 7

In a filamentous virus, the pattern of capsid monomers forms a __________ tube around the genome.

A) icosahedral
B) filamentous
C) asymmetrical
D) complex
E) helical

Question 8

Icosahedral viral capsids take the form of a polyhedron with 20 identical __________ faces.

A) helical
B) filamentous
C) rectangular
D) triangular
E) asymmetrical

Question 9

__________ can be counted as representing individual infectious virions from a phage suspension.

A) Plaques
B) Viruses
C) Genomes
D) Proteomes
E) Burst size

Question 10

All of the following are true about the measles virus EXCEPT:

A) It is encased by an envelope of membrane.
B) It fuses with the host cell membrane during infection.
C) It has progeny that bud out of the host cell.
D) It generates a rash of red spots on the skin of infected patients.
E) It is never fatal.

Question 11

An icosahedral capsid has how many sides?

A) 4
B) 6
C) 8
D) 10
E) 20

Question 12

Infectious agents for which the nucleic acid genome is itself the entire infectious particle are called:

A) prions
B) viroids
C) viruses
D) bacteria
E) virions

Question 13

Spontaneous __________ diseases can be inherited genetically.

A) prion
B) viroid
C) virus
D) virion
E) bacterial

Question 14

Tegument proteins may be found:

A) in the capsid
B) between the capsid and envelope
C) in the envelope
D) in the nucleus
E) in the spikes

Question 15

The RNA genome of the potato spindle tuber viroid requires which type of modified host polymerase for replication?

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

Question 16

Large __________ viruses contain so many enzymes that they appear to have evolved from degenerate cells.

A) icosahedral
B) filamentous
C) complex
D) bacteriophage
E) asymmetrical

Question 17

Which of the following is INCORRECT about the giant mimivirus?

A) It may cause human pneumonia.
B) It is as large as some bacteria.
C) It conducts DNA repair.
D) It conducts protein folding by chaperones.
E) It contains reverse transcriptase.

Question 18

Genes for the capsid proteins are found in the:

A) plasmid
B) bacterial chromosome
C) envelope
D) ribosome
E) viral genome

Question 19

An open reading frame corresponds to a series of codons that are translated to amino acids, producing a(n):

A) RNA
B) protein
C) DNA
D) capsid
E) envelope

Question 20

The destruction of cells as a result of viral lysis can be observed as a:

A) tissue culture
B) lawn
C) soft agar
D) plaque
E) host

Question 21

So far, the known mechanisms of replication and mRNA expression define how many fundamental groups of virus species?

A) 5
B) 6
C) 7
D) 8
E) 9

Question 22

Which of the following steps is NOT part of the life cycle of a lytic phage?

A) Phage DNA is injected into the bacterial cell.
B) The phage DNA integrates into the bacterial chromosome.
C) Many copies of phage DNA are made.
D) The phage DNA is transcribed, and the resulting mRNA is translated to make capsid proteins.
E) All of the above steps are part of the life cycle of a lytic phage.

Question 23

Viruses may be classified by the __________ method.

A) Annapolis
B) Baltimore
C) Orono
D) Augusta
E) Portland

Question 24

After the genome is inserted, the phage capsid remains outside, attached to the cell surface, and is referred to as:

A) an envelope
B) a neck
C) tail fibers
D) a ghost
E) temperate

Question 25

Which of the following is NOT true of the pararetroviruses?

A) They have an RNA genome.
B) They do not make a DNA intermediate.
C) Some have a viral reverse transcriptase.
D) Some use a host reverse transcriptase.
E) They consist of human and plant pathogens.

Question 26

What happens to the virus protein coat when a bacterial cell is infected?

A) It enters the host cell with the viral genome.
B) It remains on the outside of the host cell.
C) It enters the host cell separately from the viral genome.
D) It is released to attach to and inject another host cell.
E) It becomes part of the host cell membrane.

Question 27

The proteomic tree of bacteriophages is based on comprehensive analysis of viral:

A) DNAs
B) RNAs
C) proteins
D) capsids
E) host range

Question 28

The integrated phage genome is called a(n):

A) temperate
B) lysogen
C) oncogene
D) lytic
E) prophage

Question 29

A(n) __________ phage may integrate its genome into that of the host cell.

A) lytic
B) temperate
C) viroid
D) asymmetrical
E) oncogenic

Question 30

__________ are genes of common ancestry in two genomes that share the same function.

A) Homologs
B) Open reading frames
C) Proteomes
D) Orthologs
E) Lysogenic

Question 31

Proteomic analysis predicts seven major evolutionary categories of phage species with subgroups based on:

A) type of genetic material
B) virion structure
C) shared hosts
D) transcriptional strategy
E) replicase gene sequence

Question 32

A spacer is a(n):

A) bacterial gene
B) bacterial enzyme
C) piece of phage DNA
D) inactive viral RNA
E) cascade protein

Question 33

Which of the following statements regarding bacterial defenses against phage infections is FALSE?

A) Resistance to phages can occur through mutations.
B) Bacterial restriction endonucleases can cleave viral RNA genome.
C) The clustered, regularly interspaced short palindromic repeats inserted in the bacterial genome facilitate cleavage of specific phage DNA.
D) Bacterial restriction endonuclease system cleaves DNA lacking appropriate methylation patterns.
E) Resistance to phages can occur through altered host receptor proteins.

Question 34

__________ of viruses are designated with the suffix viridae.

A) Genera
B) Families
C) Species
D) Orders
E) Classes

Question 35

David Baltimore proposed that the primary distinction among classes of viruses was the __________ composition and the route used to express messenger RNA.

A) genome
B) envelope
C) capsid
D) tegument
E) neck

Question 36

A key factor in the evolution of killer strains of influenza is that they:

A) only have eight genes
B) have an RNA genome
C) contain reverse transcriptase
D) have a segmented genome
E) have a circular chromosome

Question 37

The number of virus particles released at lysis is referred to as:

A) lytic number
B) burst size
C) lysogenic number
D) temperate number
E) release number

Question 38

Which one of the viral gene products is likely to be expressed early in bacteriophage T4 life cycle to facilitate the replication of viral genome?

A) a DNase that digests host genome
B) an RNase that digests viral genome
C) a protease that digests viral capsids
D) the capsids required to produce mature viral particles
E) the ribosomes required for translation of viral mRNA

Question 39

The genome of __________ ssRNA viruses can serve directly as mRNA.

A) positive-sense (+)
B) negative-sense (-)
C) all
D) double-stranded
E) prion

Question 40

If something descended from a common ancestor, it is:

A) monomeric
B) monophyletic
C) monogrammed
D) monosyllabic
E) monolithic

Question 41

What determines whether a temperate phage will go through the lysogenic cycle or switch to the lytic cycle?

Question 42

What are prions and how do they cause disease?

Question 43

HIV is classified in a category of slowly replicating retroviruses termed:

A) picornaviruses
B) papillomaviruses
C) oncogenic viruses
D) lentiviruses
E) pararetroviruses

Question 44

What is the viral envelope composed of? How does it differ from the bacterial cell envelope?

Question 45

Mosaic genomes are genomes that are derived from different sources. How does this occur in viruses?

Question 46

Why are viruses not affected by antibiotics? Why are there so few antiviral drugs?

Question 47

Which of the following is FALSE concerning HIV?

A) It is the causative agent of AIDS.
B) It makes a DNA copy of its RNA genome.
C) Reverse transcriptase is translated from an early gene.
D) The virion contains two copies of the HIV genome.
E) The viral RNA is copied into double-stranded DNA.

Question 48

The papillomavirus is an example of:

A) latent infection
B) lytic infection
C) persistent infection
D) transformation
E) acute infection

Question 49

Some viruses require an RNA-dependent RNA polymerase. What does that mean? Using the same vernacular, what would you call the host cell RNA polymerase (RNA pol)? What would you call reverse transcriptase (RTase)?

Question 50

The period of time when virions are virtually undetectable inside the infected cell is the:

A) eclipse period
B) latent period
C) rise period
D) burst period
E) lag period

Question 51

Compare and contrast the Baltimore classification of viruses to the proteomic analysis of bacteriophages. Which more accurately reflects the significant impact of phage evolution?

Question 52

What is the advantage of symmetry in viral particles?

Question 53

Within a host, receptor molecules can also determine the __________, or tendency to infect a particular tissue type.

A) tropism
B) host range
C) virulence
D) burst size
E) plaque

Question 54

Why do many RNA viruses encode their own RNA-dependent RNA polymerase and package them in viral particles? How do we take advantage of these viral-specific polymerases?

Question 55

Hosts may benefit from infection by persistent viruses because:

A) hosts never come down with illness when infected by persistent viruses
B) persistent viruses could encode growth factors beneficial to infected hosts
C) persistent viruses shorten hosts' generation time, resulting in hosts that outcompete their competitors
D) persistent viruses could encode toxins that kill off competing bacteria
E) persistent viruses could improve hosts' efficiency in uptake of nutrients

Question 56

In contrast to animal viruses and bacteriophages, plant viruses infect cells by mechanisms that do NOT involve specific:

A) receptors
B) membranes
C) envelopes
D) vectors
E) hosts

Question 57

How can a virus be used in biotechnology to transfer genes from one bacterial cell to another?

Question 58

The primary factor determining the life cycle of an animal virus is the physical form of the:

A) envelope
B) capsid
C) genome
D) receptor
E) burst

Question 59

The flu is an example of:

A) latent infection
B) lytic infection
C) persistent infection
D) transformation
E) oncogenic infection

Question 60

Which of the following is the most common sexually transmitted disease in the United States, and one of the most common worldwide?

A) human papillomavirus (HPV)
B) human immunodeficiency virus (HIV)
C) gonorrhea
D) syphilis
E) chlamydia

Question 61

How does genome uncoating occur with animal viruses?

Question 62

Define oncogenes and oncogenic viruses, and explain how they can be used in gene therapy.

Question 63

During the eclipse period of a viral infection, why are the virions undetectable in the growth medium?

Question 64

To count the number of viruses in a solution, one can perform a plaque assay. Describe how a plaque is generated in the case of a lytic virus and how a virus that does not lyse its host can be detected.

Question 65

Discuss the role that marine viruses play in carbon balance.

Question 66

How is a plaque assay used to count virions in a solution?

Question 67

What determines the host range and tropism of a virus?

Question 68

Why was the advent of tissue culture heralded as the end of the "monkey era"? What types of things are we able to do with it?

Question 69

The myxovirus was introduced to Australia to control the rabbit population. How does the virus keep the rabbit population relatively low without killing all of the rabbits?

Question 70

What is necessary for bacteriophage and animal virus entry into a cell? How does that differ from plant viral entry?