Lecture 10 Viruses General Characteristics Flashcards

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1
Q

What type of genetic information are in viruses?

A

DNA or RNA

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2
Q

What is the genetic information in viruses contained in?

A

Protective protein coat

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3
Q

Inert particles

A

no metabolism, replication, motility

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4
Q

Genome hijacks host cell’s _____

A

replication machinery

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5
Q

Are viruses organisms?

A

No

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6
Q

What do viruses require?

A

live organism as host

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7
Q

Can viruses be grown in pure culture?

A

No

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8
Q

Which microscope are viruses NOT seen in

A

Light microscopy

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9
Q

Viruses that infect bacteria are called

A

bacteriophages

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10
Q

viruses are vehicles for what

A

horizontal gene transfer

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11
Q

what is virion

A

nucleic acid

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12
Q

What is virion surrounded by

A

capsid (protein coat)

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13
Q

Capsid is composed of what

A

Capsomeres

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14
Q

What are nucleocapsid

A

Capsid plus nucleic acids

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15
Q

What is nucleic acid

A

Either DNA or RNA, may be singular stranded or double stranded

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16
Q

_____ viruses are surrounded by lipid bilayer obtained from host cell

A

Enveloped

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17
Q

Enveloped viruses are surrounded by what layer

A

Lipid bilayer obtained from host cell

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18
Q

_____ is between nucleocapsid envelope

A

Matrix protein

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19
Q

How is non-enveloped viruses different from enveloped viruses?

A

More resistant to disinfectants

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20
Q

_____ are attached to receptor sites on host cells

A

Spikes

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21
Q

Phages attach by _____

A

Tail fibers

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22
Q

Spikes attach to _____ sites on host cells

A

Receptor

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23
Q

What are the three shapes of viruses

A

Icosahedral, helical, complex

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24
Q

What is an example of icosahedral

A

20 flat triangles

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25
Q

What is an example of helical

A

Capsomeres arranged in helix

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26
Q

What is example of complex

A

phage, icosahedral nuceleocapsid, helical protein

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27
Q

What type of virus is papillomaviridae

type of DNA, outer covering

A

double stranded DNA, non-enveloped

disease= human papillomavirus

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28
Q

What type of virus is herpesviridae

type of DNA, outer covering

A

Double stranded DNA, enveloped

disease=herpes zoster virus, herpes simplex virus

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29
Q

What type of virus is Reoviridae

type of DNA, outer covering

A

double stranded, non-enveloped, human rotavirus

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30
Q

What type of virus is Picornaviridae

type of DNA, outer covering

A

Single stranded (plus strand), non-enveloped

poliovirus, rhinovirus, hepatitis A

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31
Q

What type of virus is Caliciviridae

type of DNA, outer covering

A

Single stranded (plus strand), non-enveloped, norovirus

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32
Q

What type of virus is coronaviridae

type of DNA, outer covering

A

single stranded (plus strand), enveloped

SARS, MERS

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33
Q

What type of virus is Rhabdovirus

type of DNA, outer covering

A

single stranded (minus strand), enveloped, rabies

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34
Q

What type of virus is Paramyxoviridae

type of DNA, outer covering

A

Single stranded (minus strand), enveloped, influenza virus

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35
Q

What type of virus is hepadnaviridae

type of DNA, outer covering

A

DNA, enveloped, hepatitis B

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36
Q

What type of virus is Retrovirus

type of DNA, outer covering

A

RNA, enveloped, human immunodeficiency virus (AIDS)

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37
Q

What are viruses that are oral-fecal route called

A

Enteric viruses

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38
Q

What are respiratory route called

A

Respiratory virus

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39
Q

what is arboviruses

A

spread by arthropods, often can infect widely different speices

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40
Q

What are the three types of bacteriophages

A

Lytic, temperate, filamentous

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41
Q

What is latent state

A

Viral genome remains silent, but is replicated along the host cell genome

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42
Q

What is productive infection

A

New viral particles produced

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43
Q

Lytic phages exit the host by _________ the cell

A

Lysing

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44
Q

What type of infection is lytic phages

A

Productive infection

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45
Q

What are the 5 steps of lytic phase

A

Attachment
genome entry
synthesis
assembly
release

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46
Q

What happens in attachment phase of lytic phage

A

phage attaches to receptors

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47
Q

What happens in genome entry phase of lytic phage

A

T4 lysoszyme degrades cell wall, tail contracts, injects though cell wall, capsid remains OUTSIDE cell

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48
Q

What happens in synthesis phase of lytic phage?

A

Synthesis of phage proteins and genome

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49
Q

What happens in assembly stage of lytic phage

A

some components assemble spontaneously, others require protein scaffolds

50
Q

What happens in the release stage of lytic phage

A

lysozyme produced late in infection, digests cell wall, cell lyses, releases phage

51
Q

_________ phages can direct a lytic infection or incorporate DNA into host cell genome

A

Temperate phages

52
Q

In temperate phage infections, infected cell is _________

A

Lysogen

53
Q

In temperate phage infections, integrated phage DNA is _________

A

prophage

54
Q

What is the model of temperate phage in temperate phage infections

A

Lambda

55
Q

in temperate phages, _________ inserts phage DNA at site on chromosome

A

integrase

56
Q

_________ replicates along with host chromosome in temperate phage infections

A

prophage

57
Q

_________ prevents excision, maintains lysogenic state

temperate phage infections

A

Repressor

58
Q

if DNA is damaged, SOS repair system turns on, actives _________

A

Protease

59
Q

What is phage induction

A

Protease destroys repressor, allows prophage to be excised, enter lytic cycle

allows phage escape damaged host

60
Q

Lysogen is immune to

A

Superinfection

61
Q

What is superinfection

A

Infection by the same phage

62
Q

What is lysogenic conversion

A

Lysogen may show change in phenotype due to prophate DNA

63
Q

toxics are encoded by phage genes, only strains carrying _________ produce toxins

A

Prophage

64
Q

What are filamentous phages

A

Single stranded DNA phages, looks like long fibers

65
Q

What infections do filamentous phages cause

A

Productive infections
- host cells not killed but grow slowly

66
Q

What is model for filamentous phage

A

M13 phage

67
Q

in filamentous phages, _________ synthesizes complementary strand

A

DNA polymerase

68
Q

What is replicative form of filamentous phage

A

one strand used as template for synthesis of mRNA copies of genome

69
Q

in filamentous phages, M13 particles assembled in process of _________

A

Extrusion

70
Q

What is generalized transfuction

A

packaging error during phage assembly, some phages degrade host chromosome, fragments can be mistakenly packed into phage head

71
Q

Phages that go thru generalized transduction can’t direct _________

A

phage replication cycle

72
Q

What are phages that can’t do phage replication cycle because of generalized transduction called

A

Transducing particles

73
Q

What happens to transducing particles after they’re released

A

bind to new host, inject DNA

74
Q

DNA may integrate via _________ for transducing particles

A

Homologous recombination

75
Q

What is specialized transduction

A

excision mistake during transition from lysogenic to lytic cycle of temperate phage

76
Q

In specialized transduction, what is removed?

A

short piece of bacterial DNA

77
Q

What happens to excised DNA from specialized transduction?

A

goes into phage head, defective particles released

78
Q

What can the excised DNA do?

A

Can bind to new host, inject DNA

79
Q

What genes are transferred in specialized transduction?

A

only bacterial genes adjacent to integrated phage DNA

80
Q

Viruses only multiply inside _________

A

living cells

81
Q

What are plaque assays used to count

A

phage particles in samples like sewage, seawater, soil

82
Q

In plaque assays, zones of clearing from bacterial lysis are _________

A

Plaques

83
Q

plaque forming unit represent_________

A

single phage

84
Q

Counting plaques yields the _________

A

Titer

85
Q

What is titer

A

Concentration of phage in original sample

86
Q

First step of animal virus replication

A

attachment

87
Q
  1. attachment step of animal virus replication
  • viruses bind to recepter on _________
  • normal function of receptor molecule unrelated to viral infection
  • virus attach to receptor, limits cell _________ and _________ virus can infect
A

host cell surface

cell types and tissues

88
Q
  1. penetration and uncoating - animal virus replication
  • enveloped viruses enter by _________ or _________
  • _________ virus cannot fuse
  • entire _________ enters cell, nucleic acid separates from protein coating
A

fusion, endocytosis
non-enveloped
virion

89
Q
  1. synthesis- animal virus replication
    - expression of viral _________ to produce viral structural and catalytical genes
    - synthesized as _________ that is cleaved by viral _________
    - synthesis of multiple copies of genome
A

genes
polyprotein, protease

90
Q

Three replication strategies depending on what three viruses

A

DNA virus, RNA virus, reverse transcribing virus

91
Q

double stranded DNA is _________ to form viral genome

A

replicated

92
Q

The negative strand of double stranded DNA is transcribed to produce _________

translated to make _________

A

mRNA

viral proteins

93
Q

how is single stranded DNA replicated?

A

Complement to DNA synthesized FIRST, acts as template to produce more copies of viral genome

94
Q

in single stranded DNA replication, the _________ strand is transcribed to produced mRNA

A

Negative

95
Q

What kind of stranded are RNA viruses

A

single stranded

96
Q

Where do RNA viruses replicate?

A

cytoplasm

97
Q

RNA viruses require what enzyme

A

RNA-dependent RNA polymerase (replicase)

98
Q

What does the RNA-Dependent RNA polymerase do?

A

Allows use of RNA template to make new strand of RNA

99
Q

What genome serves as mRNA

A

+ ssRNA

100
Q

What genome is complement to RNA

A
  • ssRNA
101
Q

What genome contains both mRNA and complement to mRNA

A

+/- dsRNA

102
Q

Replication of + ssRNA virus

  • viral RNA binds to _________, produces viral replicase
  • viral replicase produces multiple copies of _________
A

Ribosome
complementary (-)

103
Q

Replication of + ssRNA virus

  • viral RNA and replicase enter host cell to make _________ strand
  • _________ strand can serve as mRNA to make proteins
  • multiple copies of _________ RNA strand produce to serve as viral genome
A

complementary +

+ RNA strand

complementary - RNA

104
Q

What MUST happen in the replication of - ssRNA virus?

A

replicase must accompany virus since first step is to make + strand

105
Q

Replication of dsRNA virus

  • _________ enters host cell with dsRNA
  • replicase uses _________ strand to produce _________ strand
  • _________ strand can serve as mRNA
A

replicase

  • RNA strand to produce + RNA strand

+ RNA strand

106
Q

Replication of RNA viruses

Replicase lacks _________ ability
- generates _________ during replication
- results in _________

A

proofreading
mutations
Antigenic drift

107
Q

In replication of RNA viruses, some RNA viruses have _________ genomes

A

segmented

108
Q

What is subtype of segmented genomes in RNA viruses?

A

antigenic shift

109
Q

Replication of reverse-transcribing

  • encodes _________ : makes DNA from RNA
  • _________ have + ssRNA
  • reverse transcriptase enters cell and synthesizes a single DNA strand
  • _________ DNA strand is synthesized, dsDNA integrated into host cell chromosome
A

reverse transcriptase
retroviruses
Complementary

110
Q

spontaneous self-assembly when viral _________ and _________ accumulate in host cell

A

nucleic acid and capsid proteins

111
Q

Most enveloped viruses leave via _________

A

budding

112
Q

Viral _________ insert into host cell membrane, matrix proteins accumulate; nucleoacapsids extruded

A

protein spikes

113
Q

Non-enveloped viruses released when host cell dies by _________ initiated by virus or host

A

apoptosis

114
Q

how many low-pathogenicity coronaviruses are endemic in humans?

A

4

115
Q

how many coronaviruses have crossed the species barrier since 2000?

A

Three

116
Q

What protein protrudes from the viral surface and resembles a crown?

A

S protein

117
Q

SARS-CoV-2 belongs to what genus?

A

B-coronavirus, coronaviridae

118
Q

SARS-CoV-2 is an enveloped or non-enveloped vrius?

A

Enveloped

119
Q

SARS-CoV-2 is what type of genome?

A

single stranded, unsegmented, +

120
Q

What are the 4 proteins in SARS-CoV-2

A

Spike glycoproteins
Envelope glycoproteins
membrane glycoproteins
nucleocapsid protines