Lecture 1- Virus Classification, Structure and Replication Flashcards
1
Q
The discovery of plant viruses was based on… and..
A
size(differentiated it from bacteria) and
growth (differentiated it from toxin)
2
Q
…. have been instrumental in developing the field of virology and expanding field of biology
A
bacteriophages
3
Q
The first animal virus discovered was….
The first human virus discovered was…
A
- foot and mouth 1898
- yellow fever virus
4
Q
VIruses are …. than bacteria, fungus and other microorganisms
A
smaller
5
Q
Viruses replicate when provided a….
A
host
6
Q
Viruses are…. parasites
A
obligate intracellular
7
Q
Are viruses autopoietic?
A
no
8
Q
Virus means… in Greek and they are… in nature
A
- poison
- ubiquitous (if theres a lifeform, theres virus that will infect it)
9
Q
2 theories of virus origin
A
- Cellular origin
2. Autopoietic origin
10
Q
The …origin theory proposes that viruses were once cellular components but over time they evolved separately
A
cellular
11
Q
The… origin theory proposes that viruses, once autopoietic entities, became dependent on cells for replication
A
autopoietic
12
Q
Attributes for virus classification (5)
A
- virus particle structure
- genome
- replication features
- serology (antibody recogn.)
- stability
13
Q
3 characteristics of particle structure
A
- composition
- shape
- size
14
Q
Virus is defined by its… structure which is defined as: RNA or DNA in a core that is protected by a protein coat (capsid)
A
Nucleocapsid
15
Q
Nucleocapsid structure symmetry (3)
A
- helical
- pleomorphic
- icosahedral
16
Q
Nucleocapsid is comprised of repeating protein subunits called…
A
capsomeres
17
Q
… are virus-modifies cellular membranes acquired upon exit from host
A
envelopes
18
Q
Exposure to lipid solvents in laboratory renders enveloped viruses…
A
noninfectious
19
Q
Enveloped viruses may have nucelocapsids with…. structures
A
different
20
Q
Viruses genome can be made up of… or… and each of these can be single or double stranded
A
DNA or RNA
21
Q
If the virus genome is made up of RNA and it’s single stranded, it can be either of these 3 types
A
1. Plus sense (+) ssRNA ready for transcription 2. Minus sense (-)ssRNA needs to be copied b4 transcr. 3. Ambisense goes both ways
22
Q
Virus structure genome can be linear, …, …., or….
A
circular, segmented, or diploid
23
Q
Unique feature of virus is that it can go from mRNA back to…
A
DNA (reverse transcription)
24
Q
(-) ssRNA, a….. needs to come in with the virus
A
polymerase
25
What do DNA viruses need that RNA viruses do not?
access to nucleus
26
What do RNA viruses need that DNA do not?
RNA dependent RNA polymerase
27
Steps of replication
1. attachment
2. entry
3. transcriptiom
4. translation
5. replication
6. assembly
7. release
28
Cellular receptors that viruses try to attach to (3)
1. signaling receptors
2. cell adhesion molecules
3. transport molecules
29
Viral receptors for attachment usually do not mimic cell receptors normal
ligands
30
Viral receptors for attachment typically are.... on particle surface
spike like projections
31
Viral receptors for attachment may require a...
co receptor
32
Attachment is a major determinant of virus...
tropism (host range that it can infect)
33
... is a major factor in eradication
```
host range
example:
smallpox-
humans
yellow fever- humans and mosquitoes
```
34
Entry of virus can be by two main mechanisms for envelope viruses
1. receptor mediated endocytosis
| 2. direct penetration of plasma membrane
35
Entry of non-enveloped virus mechanisms
- not well understood
- Pores: picornavirus
- Membrane disruption: adenovirus, reovirus
36
The enveloped virus entry mechanism is best understood for...
influenza
37
Influenza is an enveloped virus which uses what mechanism for entry?
-receptor mediated endocytosis
38
Influenze uses what protein for attachment and entry?
HA protein
39
For the influenza virus, during entry it's attachment proteins undergo...which is activated by a... which then brings the virus lipid bilayer and cell lipid bilayer into close contact which is called a ... state
- a conformational change
- low pH
- hemifusion
40
In virus replication, first... needs to occur
uncoating
41
Viruses that need to replicate in the nucleus are usually transported to the nucleus before...
uncoating
42
dsRNA viruses .... release their genomic material from the entering particle
Never
43
Viruses that replicate in the cytoplasm can release genome in cytoplasm or the genome is transported to another... site of replication
intracellular (many RNA viruses replicate in membrane associated complexes)
44
After entering/uncoating, viruses undergo ... which is production of messenger RNA (mRNA) templates for protein synthesis
transcription
45
DNA viruses usually rely on... for transcription
RNA polymerases
46
The genome of... can serve as mRNA. Production of new transcripts can occur later using...
(+)ssRNA
| (-)ssRNA
47
... and... viruses must bring their own polymerase into the cell
(-)ssRNA and dsRNA
48
After transcription, ... occurs which is...
- translation
| - production of proteins
49
All viruses need the cell's ... to produce proteins- NO exceptions
ribosomes
50
Viral protein production can be regulated at the.... or .... level
-transcript mRNA -translation
51
Structural proteins are produced in ...
high quantities
52
Non-structural proteins are only seen ...
inside the infected cell
53
The objective of genome replication for the virus is to...
make additional genome copies
54
The order of events of genome replication depends on the...
virus genome (different between viruses)
55
(+)ssRNA genome replication order of events is first the genome serves as template for... and then polymerase makes.... as template for new genomes
- translation
| - (-)ssRNA copy
56
(-)ssRNA genome replication order of events is first that the virus must bring in a... with it, and then polymerase makes... for translation and then genome replicates through full length...
- RNA dependent RNA polymerase
- mRNA
- (+)ssRNA intermediate
57
In dsRNA, virus particle includes...
viral polymerase
58
dsRNA induces innate immune response so genome stays...
| mRNA synthesized in.. and exported to...
- inside particle
- particle
- cytoplasm
59
In dsRNA, mRNA serves as (+) strand in... and (-) strand synthesized during...
- virus genome
| - assembly
60
ssDNA and dsDNA must gain access to the... for genome replication. But... are an exception
- nucleus
| - poxviruses (replicate in cytoplasm)
61
Poxviruses do not need to gain access to the nucleus because virion conatins the necessary... and the genome encodes the... for replication.
- RNA polymerase
| - DNA polymerase
62
After genome replication, ... takes place where new genomes are packaged into functional particles
assembly
63
The virus localizes... to aid in assembly (cellular viral "factories"
structural proteins
64
Adenovirus assembly mechanism
empty protein coat imports genome
65
Reovirus assembly mechanism
RNA packaged during capsid assembly
66
Retrovirus assembly mechanism
preassembly on a membrane
67
Release of viruses can be either... or ...
lytic (causes cell rupture) or non-lytic (dont kill cell)
68
Budding (enveloped only is an example of .... viral release and the disease... uses this mechanism
non lytic
| -HIV
69
Lysis release is best known for... and is when viral molecules... the cellular membrane
- bacteriophage
| - rupture
70
Weak lysis depends on... after cell death
membrane breakdown
71
Budding is when ... viruses use... as the outer coat of the virus particle
- enveloped
| - cell membrane
72
Advantage of virus replication in the nucleus is that there are ...
-polymerases and resources for replication
73
Disadvantage of virus replication in nucleus
more steps to get to the nucleus and have to get across nuclear pore
74
The kinetics of virus replication is a.... curve meaning they infect every cell at... and every cell... at end of infection
- one step growth
- same time
- dies
75
The phases of the virus replication one step growth curve are... (3)
1. eclipse
2. exponential growth
3. plateau
76
The eclipse phase of virus replication growth curve represents...
attachment and uptake
77
The exponential growth phase of virus replication growth curve represents...
replication and assembly
78
The plateau phase of the virus replication growth curve represents...
cell death
79
One step growth curves are useful to assess: (3)
1. mutations
2. cell entry
3. process design
80
Vaccinia virus is a lytic or non-lytic virus?
lytic
81
The time for one step growth is measured from start of.. to beginning of..
- infection
| - plateau
82
The... is known for having one of the fastest one step growth - 30 minutes
bacteriophage
83
... has a decently fast one step growth at 6 hours and only infects animals
Vesicular stomatitis virus (VSV)
84
The time for one step growth in the Vaccinia virus is .. which is common for most viruses if not longer usually
24 hours
85
Productivity of VSV and Vaccinia
VSV 1:1000
| Vaccinia 1:100
86
Detection and quatification of viruses: 1st step is... and 2nd step is...
1. initial discovery
| 2. confirmation
87
Initial discovery of a virus will be either by ... in a host of ... in cell culture
- disease
| - contaminant
88
Confirmation of a virus
1. purification
2. confirmation of disease
3. cell culture is preferred
89
Principle detection and quantification methods can be the following types
1. infectivity
2. physical
3. genome
4. serological
90
Molecular methods are useful for viruses that cannot be...
cultivated
91
One infection assay is cytopathic effect which can be identified by these 3 characteristics
1. cell rounding
2. syncytia formation (fused cells)
3. inclusion bodies
92
Another infection assay is fluorescent focus assay where you infect and stain cells with... and then see how it spreads
-a labeled antibody
93
Infectious dose assays is done by inoculating with different dilutions of virus and calculating... based on number infected
-concentration
94
2 types of particle assays
1. electron microscopy
| 2. hemagglutinin assay
95
2 types of genomic assays
1. Polymerase chain reaction
| 2. Southern and Northern (DNA) Blots
