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micro exam 3 > Virus Classification, Structure, and Replication > Flashcards

Virus Classification, Structure, and Replication Flashcards

1
Q

how is a virus different from a bacterium

A

size

obligate intracellular parsite

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2
Q

how is a virus different for a toxin

A

toxin does not replicate

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3
Q

How did we discover that viruses were small

A

Dimitri IVanofsky showed that Tobacco Mosaic Virtus was able to pass through a filter while bacteria could not
then afterwards the electron micrograph

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4
Q

how did we discover the growth(non-toxin) of viruses

A

Martin Beijerinck showed that the titer of Tobacco mosaic Virus increased after infecting a plant

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5
Q

how was the bacteriophage discovered

A

Frederick W. Twort while trying to grow vaccinia virus (1915)

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6
Q

The first animal virus discovered

A

Foot and Mouth disease (1898)

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7
Q

The first Human virus discovered

A

yellow fever virus (1901)

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8
Q

research use of bacteriophage

A

instrumental in developing the field of virology and biology

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9
Q

are Virus autopoietic

A

no (obligate intracellular parasites

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10
Q

Theories for virus origin

A

Cellular origin

Autopoietic origin

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11
Q

the Cellular origin of viruses state that

A

viruses were once cellular components, but over time they evolved separately

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12
Q

the autopoietic origin of viruses state that

A

viruses, once autopoietic entities, became dependent on cells for replication

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13
Q

ways to classify viruses

A 
Virus particle strucutre
Genome (size, genes, copies)
replication features
Serology (antibody recognition)
Stability
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14
Q

what defines Virus PArticle strucutre

A

Composition
Shape
Size
envelope or nonenvelop

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15
Q

What makes up the Nucleocapsid

A

RNA or DNA in a core that is protected by a protein coat (capsid)

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16
Q

tyoes of Nucleocapside strucutres

A

Helical
Pleomorphic
Icosahedral

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17
Q

Helical Nucleocapsid Structure

A

Genome coiled around with proteins surrounding it

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18
Q

pleomorphic nucleocapside strucutre

A

blob

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19
Q

the repeating portein subunites of the nucleocapside

A

Capsomere

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20
Q

Virus-modified cellular membranes acqueired upon exit from a host

A

Envelopes

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21
Q

what does exposure to lipid solvents in the lab (Alcohol, ether, acetone, freon, etc) do to enveloped viruses

A

makes them noninfectious because evelope proteins are important for the infectious cycle

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22
Q

what makes up the envelope of a virus

A

lipid bilayer

viral proteins and host cell proteins

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23
Q

is the shape of the envelope related to the shape of the nucleocapside

A

no relation (nucleocapsid can be any shape desired)

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24
Q

smallest and largest virus

A

18nm:
300nm: pox-virus family

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25
Q

advantage of small virus

A

taken up easier

move easier

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26
Q

advantage of large virus

A

can bring more stuff to aid in infection

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27
Q

possible types of Genomes of Viruses

A

DNA: double stranded, Single stranded
RNA: Double Stranded
Sing Stranded: plus sense, minus sense, or ambisense

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28
Q

plus sense ssRNA

A

ready for translation

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29
Q

minus sense ssRNA

A

must be copied before it can be translated

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30
Q

ambisense ssRNA

A

can be both minus or plus sense ssRNA

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31
Q

Virus Genome structures

A

Linear
Circular
Segmented
Diploid

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32
Q

Central Dogma

A

Replication of DNA
DNA transcribed into RNA or RNA reverse transcribed into DNA(viruses only
RNA translated to protein

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33
Q

replication via ssDNA hairpin

A

ssDNA folds to look like dsDNA right were DNA polymerase binds

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34
Q

Replication via dsDNA rolling circle

A

makes a copy with a lagging strand also to eventually give a double stranded DNA

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35
Q

replication via +ssRNA

A

genome enters, and is template for protein
these proteins made can be a polymerase that binds to RNA struutre, to make a negative sense to serve a template to make a bunch of offspring

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36
Q

Relication via -ssRNA

A

polymerase comes in with the virus to sit on -ssRNA to make the plus sense copies that are eventualy turned into proteins

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37
Q

advantage and disadvantage of large genomes

A

ad: more proteins
disadvantge: higher chance of detection, longer time, greater chance of error

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38
Q

what do most DNA viruses need that RNA viruses do not?

A

need transcption machinery

access to the nucleus

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39
Q

what do most RNA viruses need that DNA viruses do not

A

need an RNA depended RNA polymerase

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40
Q

steps of Virus Replication

A 
Attachment
Entry
TRanscription
Translation
Replication
Assembly Release
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41
Q

the binding of a virus receptor to a cellular receptor

A

Attachment

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42
Q

Cellular receptors(parts of the cell that actually have cellular roles) that are targets for viruses to bind

A

Singaling Molecules
Cell adhesion molecules
Transport molecules

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43
Q

do viral receptors mimnic cell receptor’s normal ligands

A

No

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44
Q

what do viral receptors look like

A

spike like projections on particle surface

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45
Q

what may be needed to a viral receptor to bind?

A

A co-receptor

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46
Q

how can you change receptor recognition

A

Genetic engineering

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47
Q

types of Genetic engineering to change receptor recognition

A

Changing to RGD sequeces

pseudotyping particles

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48
Q

do Viruses need to only bind to one receptor on a cell

A

no, some may need to bind to multiple

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49
Q

what determines Virus Tropism(host range)

A

attachment is a major determinant

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50
Q

what can virus’s infect

A

essentially all known forms of life, but have specific host ranges and not shared across more divergent host

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51
Q

what is a major factor in eradication of a virus

A

Host rnage

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52
Q

who could Smallpox infect

A

only human

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53
Q

who could Yellow fever infect

A

Mosquitoes and humans

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54
Q

pathways of how a virus can enter a cell

A

Receptor mediated endocytosis

Direct penetration of the plasma membrane

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55
Q

how do non-eveloped viruses enter the cell

A

No well understood
Pores
Membrane disruption

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56
Q

what is non-eveloped virus that enters cell through pores

A

Picornavirus

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57
Q

what is a non-eveloped cirus that enters cells through membrane disruption

A

adenovirius, reovirus

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58
Q

how does the enveloped (influenza) virus enter the cell

A

Via membrane fusion
HA protein allows for arrachment and fusion
this caused a drop in pH and attachment proteins undergo a confirmational change and virus lipid bilayer and cellular bilayer come close togther and mingle, creating a pore and virus gets in

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59
Q

what must a virus do once inside the cell to begin replication process

A

Uncoating

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60
Q

types of Virus replication

A

Nuclear replication

Cytoplasmic replication

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61
Q

where uncoating occures in nuclear replication

A

genome and remaining protein coat are transported to the nuclear membrane to deliver the genome to the nucleus

62
Q

where uncoating occures in cytoplasmic replication

A

Relase of the genome into the cytoplasm

transportation of the genome to intracellular site of replication

63
Q

where do many RNA virus replication in dytoplasmic replication

A

In membrane associated complexes

64
Q

do dsRNA viruses release their genomic material from the entering particle

A

No

65
Q

DNA and RNA nucleocapsides prefer what kinds of replication

A

DNA: Nuclear
Cytoplasmic: Cytoplasmic

66
Q

Pruduction of mRNA templates for protein synthesis

A

Transcription

67
Q

what do DNA viruses depend on for TRanscription

A

Cellular RNA polymerases

68
Q

the genome of what type of virus can serve as mRNA

A

+ssRNA

69
Q

how does +ssRNA create new transcriptis

A

use a -ssRNA template

70
Q

what types of virus must bring their own polymerases into the cell for transcription

A

(-)ssRNA and dsRNA

71
Q

what must a virus do to cellular transcription

A

must subvert the cells transcription

72
Q

The production of proteins

A

Translation

73
Q

what do all viruses need from the cell to produce protein

A

need ribosomes (no exceptions)

74
Q

where can viral protein production be regulated

A

at the trascript (mRNA) level of translation level

75
Q

what type of viral protein are made in high quantities

A

structural proteins

76
Q

what type of proteins are only seen in the infected cell

A

non-structural proteins

77
Q

Objective of genome Replication

A

make aditional genome copies

78
Q

what does the order of viral replication depend on

A

Virus genome

79
Q

(+)ssRNA has what as a template for translation

A

genome

80
Q

how does (+)ssRNA make new genomes

A

Polymerase(made from the (+)ssRNA) makes (-)ssRNA copy as template for new genomes

81
Q

what must be included with (-)ssRNA Virus particles for viral replication

A

Viral Polymerase

82
Q

how is the Genome of (-)ssRNA replicated

A

through full-length (+)ssRNA intermediate

83
Q

what does dsRNA contain for viral replication

A

Viral Polymerase

84
Q

why must dsRNA stay inside the particle

A

induces innate immune response

85
Q

how is mRNA made for dsRNA viruses

A

synthesized in particle and exported to the cytoplasm

86
Q

how is viral genome replicated in dsRNA

A

mRNA serves (+) strand in virus genome, (-) strand synth during assembly

87
Q

where does ssDNA and dsDNA go to do genome replication

A

must gain access to the nucleus

88
Q

what dsDNA/ssDNA virus does not need to go to the nucleus to do replication

A

Poxviruses

89
Q

why does the Poxviruse not need to go to the nucleus to do genome replication

A

virion contains necessary RNA polymerase and the genome encodes the DNA polymerase for replication

90
Q

what does the ssDNA and dsDNA of a virus do once in the nucleus and why

A

prepares the cell for DNA replication (growth phase, dNTP production, replication machinery) to ensure that the genome ends up copied

91
Q

Packaging new genomes into functional particles

A

Assembly

92
Q

what aids in assembly

A

localize structural proteins

Genome contains packaging signals

93
Q

localize structural proteins that aid in assembly

A

cellular viral “factories”

94
Q

mechanisms of Assembly

A

Adenovirus
Reovirus
Retrovirus

95
Q

when an empty protein coat imports a genome

A

adenovirus

96
Q

when RNA is packaged during capside assembly

A

Reovirus

97
Q

preassembly of virus on a membrane

A

Retrovirus

98
Q

type of infections

A

Lytic: cell is exploded

Non-lytic: cell does not explode and may be continuously secreted as a result

99
Q

how Viruses may be released

A

Lysis
Weak Lysis
Budding

100
Q

what type of virus is best known for lysis

A

BActeriophages

101
Q

when viral molecules rupture cellular membrane

A

Lysis

102
Q

weak lysis depends on

A

membrane breakdown after cell death

103
Q

what type of virus can do budding

A

only enveloped

104
Q

when enveloped virus use cell membrane as the outer coat of the virus particle

A

Budding

105
Q

what disadvantage come with targeting virus replication in the nucleus

A

Disadvantage: have to get across membrane

106
Q

how does understanding a virus replication process help design antivirals

A

find the unique parts of the virus, minimizing illness

107
Q

advantage and disadvnatage of lytic infectinos

A

advantage: dumps contents of cell with lots of viral products can infect other cells quickly, releases a lot of viruses
disadvantage: allows the immune sytem to respond to broken cells, hard to go undetected

108
Q

how to measure growth curve of Viruses

A

One step growth curve

109
Q

what is a one step growth curve

A

infect every cell at same time

every cell dies at end of infection

110
Q

phases of Virus Replication

A

Eclipse
Exponential growth
Plateau

111
Q

Eclipse phase

A

Attachment and uptake

112
Q

Exponential growth phase

A

replication and assembly

113
Q

plateau phase

A

cell death

114
Q

uses of Viral Kinetics (one step)

A

Mutations
Cell entry
Process Design

115
Q

time for one step growth

A

start of infection to beginning of plateau

116
Q

time for one step growth of bacteriophage

A

30 min

117
Q

time for one step growth of Vesicular stomatitis virus (VSV)

A

6 hours

118
Q

time for Vaccinia one step growth

A

24 hours

119
Q

productivity of a virus meaures

A

amplification of the virus

120
Q

productivity of VSV

A

1:1000

121
Q

productivity of Vaccinia

A

1:100

122
Q

how do we initialy discover a virus

A

Disease in a host

Contaminant in cell culture

123
Q

how do we confirm a virus

A

Purification and confirmation of disease (cell Culture is prefered)

124
Q

where do we confirm a disease

A

Animals, eggs, or cell cultures

125
Q

detection and Quantification methods of a virus

A

Infectivity
physical
Genome

126
Q

what method is used to detect and quantify viruses that connot be cultivated

A

Molecular Methods

127
Q

types of Infection assays

A

Cytopathic effect
Fluorescent Focus Assay
Plaque Assays
Infectious Dose

128
Q

what are cytopathic effects

A

Cell Rounding
Syncytia Formation
Inclusion bodies

129
Q

when viruses cause cell death that causes cells to round out and separate

A

Cell Rounding

130
Q

what is formed when a virus has proteins on its surface that instigate membrane fusion that cause cells to fuse together and have multiple nuclei in one cells

A

Syncytia formation

131
Q

how is a Fluorescent Focus Assay used to detect and Quantify Viruses in Infection Assays

A

Infect cells
Expose Virus Antigen
Stain with labeled antibody
Count areas that fluoresce

132
Q

How is a Plaque assay used to detect and quantify viruses in infection assays

A

there is a Cell monolayer
Innoculate with a v. dilute virus
Use a new layer of auger to ensure that virus and cells do not move
Infected cells die leaving a clear area- a plaque

133
Q

examples of infectious doses

A

ID50, IU50, TCID50

134
Q

systems used to measure infectious dose

A

Tissue Culture, Eggs, Animals

135
Q

how to measure infectious dose

A

inoculate with different dilutions of virus

Calculate concentration based on number infected

136
Q

Types of particle assays

A

Electron Microscopy

Hemaggultinin assay

137
Q

what does Electron microscopy show of a virus

A

a direct image of virus particles

compare to latex bead standard size

138
Q

how to calibrate electron microscopes

A

latex bead standard

139
Q

what type of virus is used in Hemagglutinin assays

A

Viruses that bind red blood cells (RBCs)

140
Q

how to do Hemagglutinin assays

A

mix constant number of RBCs with various virus dilutions
if virus concentration is sufficient, a matrix of RBCs and viris is formed
matrix does not allow RBC to pellet out in a centrifuge

141
Q

Genome assay types

A

Polymerase CHain Reaction
Southern (DNA) blots
Northern (RNA) blots

142
Q

How a polymerase chain reaction works

A

DNA primer is specific to a virus

Amplify that one gene

143
Q

sensitivity of Polymerase Chain reactions

A

Very sensitive

144
Q

what is done in a southern and Northern Blot

A 
Isolate DNA (Southern blot) or RNA (Northern blot) by electrophoresis-lebeled
Use a labeled DNA probe to detect
145
Q

types of Serological assays

A

Viral Neutralization
Enzyme link Immunosorbant Assay (ELISA)
Western (Protein) Blot

146
Q

antibody binding to a virus does what

A

block infection

147
Q

how to determine Virus Concentration

A

by the amount of antibody needed (Virus neutralization

148
Q

what is an enzyme Immunosorbant ASSAY (ELISA

A

Antibody recognizes virus

Amplication by enzyme linked to antibody

149
Q

Western blot

A

separate proteins by electrophoresis

Probe proteins using an antibody

150
Q

does the way we quantify a virus give different answers?

A

yes

151
Q

particle to PFU ration ranges from

A

1:1-1:10000

152
Q

how could someone get a .3 PFU

A

if humans were a better candidate for infection than a plaque

micro exam 3 (15 decks)

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