Lecture 8 Flashcards
1
Q
Viruses contain a ___ or ___ genome that codes for functions required for _________
A
DNA or RNA, self perpetuation
2
Q
The viral genome is enclosed in a protective coat called
A
the capsid
3
Q
What is the function of the capsid? (2)
A
- Protects the genome
- Ensures the attachment into susceptible cells
4
Q
a virus particle is called a
A
virion
5
Q
What are the two portions of the life cycle for viruses and what do they do?
A
- extracellular phase: virus particles (virions) aren’t metabolically active
- intracellular phase: virus genome expression and production of new virus progeny occurs
6
Q
viruses are classified as what kind of pathogens?
A
obligate intracellular pathogens
7
Q
At the minimum, all viruses have
A
- A DNA or RNA genome
- A capsid, a protein shell
- A polymerase
8
Q
What else can viruses have on top of the minimum?
A
- Envelope, a lipid membrane
- Spiked proteins
9
Q
Classification of Viruses: Group I
A
dsDNA
10
Q
Baltimore Classification of Viruses: Group II
A
ssDNA
11
Q
Baltimore Classification of Viruses: Group III
A
dsRNA
12
Q
Baltimore Classification of Viruses: Group IV
A
(+) ssRNA
13
Q
Baltimore Classification of Viruses: Group V
A
(-) ssRNA
14
Q
Baltimore Classification of Viruses: Group VI
A
RNA retroviruses (+)
15
Q
Baltimore Classification of Viruses: Group VII
A
DNA pararetroviruses
16
Q
where can viral genomes be found in our own genomes? (2)
A
- placenta
- syncytin
17
Q
viruses infect what forms of living cells?
A
ALL OF THEM
18
Q
Peyton Rous discovered what?
A
some viruses can cause cancer! (based on the picture)
19
Q
what was the conclusion of the Hershy-Chase experiment?
A
DNA (not protein) is the genetic material
20
Q
Temin Baltimore discovered what kind of virus?
A
retrovirus
21
Q
what makes retroviruses different?
A
they use reverse transcriptase to turn viral RNA into DNA to be used in host cells to create more DNA
22
Q
non-envelope viruses include…
A
adenoviruses
23
Q
What do the nucleocapsid of non-envelope viruses contain?
A
nucleocapsid contains attachment proteins
24
Q
envelope viruses contain
A
attachment proteins
25
viral envelopes are made of _____ and are sensitive to _____ and _____
lipids; detergent, bleach
26
T/F: non-envelope viruses are sensitive to detergent
FALSE- they are not sensitive to detergen
27
capsids can have what kind of symmetry? (3)
- helical
- icosahedral
- complex
28
capsomere
building blocks of capsids
29
tube length reflects what about the viral genome?
size of the genome
30
complex capsids can be shaped like what..?
a mixture of icosahedral and filamentous shapes
31
T/F: viral genomes can be both RNA and DNA at the same time
FALSE- they can be either RNA or DNA but not both
32
visual classifications of the viral genome (6)
- single stranded
- double stranded
- circular
- sense (+) or antisense (-)
- segmented
- double stranded segmented
33
viroids only contain..
RNA, no protein
34
what are viroids capable of infecting?
plants
35
prions contain...
only protein, no nucleic acids
36
T/F: all viruses have envelopes
FALSE
37
T/F: all viruses have to produce mRNAs during their life cycles
TRUE
38
Viral genomes can be which of the following configurations?
- DNA
- dsRNA
- ss(+) RNA
- ss(-) RNA
- All of the above
all of the above
39
what must viruses be grown in to study them?
in living cells
40
to study animal and plant viruses, they may be grown in what?
cell cultures
41
cytopathic effect
refers to structural changes in host cells that are caused by viral invasion
42
animal viruses may be grown in what? (2)
- living animals
- embryonated eggs
43
supernatant
denoting the liquid lying above a solid residue after crystallization, precipitation, centrifugation, or other process
44
one-step growth curve experiment (6)
1. infect cells in suspension
2. incubate at 37ºC
3. take samples at time of infection and then 1 hr intervals
4. separate cells from culture supernatant
5. make serial dilution of both cells and supernatant
6. do plaque assay
45
what is a common way to measure the amount of virus in a colution?
'plaque forming units' (PFU)
46
multiplication of viruses: attachment
Virus binds to a specific receptor, and the presence or absence of these receptors largely dictates virus tropism - the ability of a virus to infect some cell types but not others
47
multiplication of viruses: penetration (enveloped vs nonenvoloped)
The virus has to actually get inside the cell. Many have to get their genetic material across the cell membrane. Enveloped viruses do this by causing fusion between their membrane and that of the cell, while nonenveloped viruses either make a pore or actually disrupt the membrane
48
multiplication of viruses: uncoating
The viral genome is tightly compacted within the capsid, so the capsid has to ‘uncoat’ in order for replication to proceed. Very little is known about this step.
49
multiplication of viruses: transcription, translation, replication
The order in which these occurs depends on the nature of the viral genome (coming up). Basically, you have to make viral proteins, you have to make viral RNA, and you have to replicate the viral genome in order to make new viruses.
50
multiplication of viruses: assembly
all of the pieces are put together to make new virus particles
51
multiplication of viruses: release
The newly assembled viruses have to be released from cells some how. The cell can be lysed, the viruses can be secreted, or they can ‘bud’ from the cell surface.
52
bacteriophage life cycles (6)
1. attach to host cell receptor proteins
2. inject genome through cell wall to cytoplasm
3. replicate genome
4. synthesize capsid proteins
5. assemble progeny phage
6. lyse cell wall to release progeny
53
eukaryotic virus life cycle (2)
1. attachment to host cell receptor
2. fuses to the plasma membrane
54
what does a virus receptor do? (4)
- binds the virus to the cell
- can just act to tether viruses
- can trigger conformational changes in capsid or glycoprotein needed for entry
- may send signals to cell
55
tropism
the spectrum of tissues and cell types infected by a given virus
56
tropism is often explained by the presence or absence of what?
the appropriate viral receptor
57
which is more common, a virus binding to one receptor or more then one receptor?
only one receptor
58
viral DNA must go where in the cell to replicate? why?
the cell nucleus to use the host polymerase (or replicate in cytoplasms with viral polymerase like Poxvirus)
59
why must RNA viruses encode a viral polymerase?
host cells cannot read RNA to make more RNA
60
why can (+) ssRNA be infectious?
(+) ssRNA can be translated to make viral proteins
61
(-) ssRNA and retrovirus genomes must be _____ to be able to be translated
replicated
62
(-) ssRNA must be converted into _____ (_____) by the RNA dependent RNA polymerase incorporated in the virion
(+) RNA; mRNA
63
how different viruses replicate their genomes: DNA genomes
they are large viruses like pox-, herpes- and encode many of the enzymes required (like DNA polymerase) and are more autonomus
64
how different viruses replicate their genomes: RNA genomes
encode their own RNA-dependent RNA polymerase which uses a complementary RNA template
65
how different viruses replicate their genomes: retrovirus
copy (+) ssRNA genome into dsDNA, which is the template for new genome synthesis
66
keypoint about RNA viruses
RNA-dependent polymerases lack proofreading so RNA viruses mutate quickly and often replicate faster
67
why do DNA viruses mutate less often?
they have access to proofreading
68
recombination
exchange of information between two genomes
69
Animal (-) strand RNA viruses always carry into the host cytoplasm their own what? (2)
genome and polymerase protein
70
Which of the following is NOT utilized to culture viruses?
- lab animals
- culture media
- embryonated eggs
- animal cel cultures
- bacterial cultures
culture media
71
A clear are against a confluent "lawn" of bacteria is called a what?
pock
72
The following steps occur during multiplication of the herpesviruses. Which if the third step?
- attachment
- biosynthesis
- penetration
- release of progenies
- uncoating
uncoating
73
Which one of the steps does not occur during multiplication of a picornavirus?
- synthesis of + strands of RNA
- synthesis of - strands of RNA
- synthesis. of viral proteins
- synthesis of viral DNA
- none of the above
synthesis of - strands of RNA
