Deck 6: Virus Structure and Function

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

An icosahedral capsid has how many sides?

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

Answer 2

E

Question 3

Which epidemic is NOT virusborne?

A) AIDS
B) bubonic plague
C) polio
D) SARS
E) smallpox

Answer 3

B

Question 4

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

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

Question 5

Genes for the capsid proteins are found in the:

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

Question 6

The RNA genome of the potato spindle tuber viroid requires which type of host polymerase to replicate itself?

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

Question 7

Degenerate viral genomes from ancient viral insertions take up __________ the human genome.

A) 1/16
B) 1/8
C) 1/4
D) 1/2
E) 3/4

Question 8

An open reading frame corresponds to a series of codons that are translated to amino acids producing a/an:

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

Question 9

Which is a unique macromolecule present in some viruses that is a target for antiviral agents?

A) ribosomes
B) DNA
C) RNA
D) reverse transcriptase
E) cytoplasm

Question 10

__________ 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 11

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 12

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 13

Virus particles can be observed by standard transmission 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 14

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 15

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 16

Spontaneous __________ diseases can be inherited genetically.

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

Question 17

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 18

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

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

Question 19

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

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

Question 20

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

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

Question 21

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

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

Question 22

If something descended from a common ancestor, it is:

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

Question 23

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

A) only have 8 genes
B) have an RNA genome
C) contain reverse transcriptase
D) have a segmented genome
E) have a circular chromosome

Question 24

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 25

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 26

__________ 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 27

Viruses may be classified by the __________ method.

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

Question 28

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 29

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 30

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

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

Question 31

One of the first genes expressed by bacteriophage T4 encodes:

A) a DNase
B) an RNase
C) a protease
D) the capsid
E) ribosomes

Question 32

__________ of viruses are designated with the suffix viridae.

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

Question 33

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 of 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 34

After the genome is inserted, the phage capsid remains outside, attached to the cell surface, and is referred to as a/an __________.

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

Question 35

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 36

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 37

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

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

Question 38

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

Question 39

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 40

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 41

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 42

Why was the 2009 influenza virus called the swine flu? How was it transmitted and why were people so concerned?

Question 43

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

Question 44

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 45

The flu is an example of:

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

Question 46

What determines the host range and tropism of a virus?

Question 47

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 48

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

Question 49

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

Question 50

HIV is classified in a category of slowly replicating retroviruses termed __________.

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

Question 51

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

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

Question 52

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 53

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 54

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 55

The integrated phage genome is called a/an __________.

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

Question 56

What are prions and how do they cause disease?

Question 57

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

Question 58

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 59

What is the advantage of symmetry in viral particles?

Question 60

The papillomavirus is an example of:

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

Question 61

How does genome uncoating occur with animal viruses?

Question 62

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 63

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

Question 64

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 65

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

Question 66

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

Question 67

Discuss the role that marine viruses play in carbon balance.

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

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

Question 70

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