Viral Classification- Aucoin Flashcards
1
Q
Viruses are (blank) agents.
A
Fiterable (can pass through a filter)
2
Q
Viruses are (blank) intracellular parasites
A
obligate (restricted to a particular condition of life)
3
Q
Can viruses make energy or proteins independently of a host cell?
A
NOOOOO
4
Q
Viral genomes can be RNA, DNA or both?
A
They can be RNA or DNA but not both
5
Q
Which do viruses have, a naked capsid or an envelope morphology?
A
Either or :)
6
Q
Are viruses living?
A
no, they are not
7
Q
What must viruses be to endure in nature?
A
infectious
8
Q
Viruses have been optimized by (blank) and (blank) to infect humans and other hosts
A
mutation and selection
9
Q
Viruses must be able to use (blank) to produce their components
A
host cell processes
10
Q
Viruses must encode any required processes not provided by the cell. T or F
A
T
11
Q
Viral components (blank) assemble
A
self
12
Q
What are the 2 types of viruses you can have?
A
naked capsid viruses enveloped viruses
13
Q
What makes up a naked capsid virus?
A
DNA or RNA + structural proteins +/- enzymatic and nucleic acid binding proteins= nucleocapsid=naked capsid virus
14
Q
What are three examples of naked capsid viruses?
A
papilloma virus adenovirus poliovirus
15
Q
What makes up an enveloped virus?
A
DNA or RNA + nucleocapsid + glycoproteins and membrane= enveloped virus
16
Q
What are 2 examples of an enveloped virus?
A
herpesvirus retrovirus
17
Q
What is a bacteriophage?
A
a virus that infects bacteria
18
Q
Many viral proteins are packaged within the virion, possibly in the (blank) layer, between the capsid and envelope
A
tegument
19
Q
What is a virion made up of?
A
nucleic acid genome packaged into a protein coat (capsid or ribonucleocapsid) or a membrane (envelope)
20
Q
What is a virion?
A
infectious virus particle
21
Q
(blank) can hold a larger genome and are generally more complex
A
larger virions
22
Q
(blank) are almost visible with a light microscope (300 nm) this i 1/4 the size of staph
A
poxviruses
23
Q
How do you measure virions?
A
in nanometers
24
Q
What are the + RNA via DNA E viruses?
A
Retro
25
What are the +/- RNA (double capsid) viruses?
Reo
26
What are the -RNA E viruses?
Rhabado Filo Orthomyxo Paramyxo Bunya Arena
27
What are the + RNA E viruses?
Toga, Flavi, Corona
28
What are the + RNA N viruses?
Picrona, Calici
29
What are the four ways you can name RNA viruses by their physical and biochemical characteristics?
+RNA (N and E) -RNA (E) +/- RNA (Double Capsid) + RNA via DNA (E)
30
How can you name DNA viruses by their physical and biochemical characteristics?
DNA viruses can be broken into eneveloped and naked capsids. They can then be further broken down into: enveloped-\> pox, herepes, hepadna naked capsid-\> polyoma, papilloma, adeno, parvo
31
What are the ways of classifying and naming viruses?
structure, biochemical characteristics, disease, means of transmission, tissue or organ (tropism)
32
What is the smallest DNA virus? What is the largest DNA virus?
Parvovirus Poxvirus
33
What is the smallest RNA virus? What is the largest RNA virus?
Picornavirus Paramyxovirus
34
What is on the surface of the capsid or envelope that will mediate the interaction of the virus with a target cell.
Viral attachent protein (VAP)
35
What do you call antibodies that attack the VAP proteins?
neutralizing antibodies
36
Is the capsid a rigid structure or a floppy structure?
rigid
37
Viruses with naked capsids are resistant to what?
Drying, acid, detergents
38
What does the viral envelope contain and how can we maintain this structure?
lipids, proteins, glycoproteins In aqueous solutions (therefore it is transmitted in body fluids)
39
Can capsids be helical (rods)?
yes!
40
How do you get a helical (rod) capsid?
self-assemble on the RNA genome- creating a ribonucleocapsid
41
Where do you find most helical capsids?
NEGATIVE-STRAND RNA VIRUSES
42
Other than helical, what other form can capsids be?
icosahedrons
43
What do icosahedrons capsids look like?
a sphere (assembled from symmetrical subunits)
44
Simple icosahedrons like picornaviruses are made up of (blank) capsomeres, each with fivefold symmetry (pentamer)
12
45
So what are capsomeres?
they are the individual units of a capsid. i.e capsomeres make up a capsid
46
What is the viral envelop composed of?
lipids, proteins, and glycoproteins (cellular membrane)
47
The envelope is formed from the (blank)
cellular membrane
48
Most (blank) act as VAPs that bind to target cells to initate entry. VAPS that bind to red blood cells are (Blank)
glycoproteins hemagglutinins
49
The glycoproteins can form the (blank) on viruses and are usually (blank)
spikes immunodominant
50
T or F all of the negative strand RNA viruses are enveleoped
T
51
(blank) is a negative strand RNA virus that contains a segmented genome
Influenza A (orthomyxovirus)
52
What is the tegument layer?
layer situated between the envelope and nucleocapsid- Contains enzymes, and other ptoeins that facilitate viral infection.
53
What all do the host cells provide for viral replication?
substrates, energy and some of the machinery :)
54
What are the phases of viral replication?
virus must recognize target cell, attach and penetrate PM. Uncoat its genome into cytoplasm and deliver genome to nucleus (sometimes). Genome replication and viral macromolecular synthesis followed by viral assembly and release.
55
What is latency
when extracellular infectious virus is not detected but viral genomes can be detected
56
What determines which cells can be infected by a virus?
the binding of the VAP to receptors on the cell
57
Viruses may bind to receptors on cell types of specific species only. What do you call this?
host range
58
THe suceptible target cell defines the (blank)
tissue tropism
59
VAPs are usualy specific (blank) of enveloped viruses.
glycoproteins
60
The HA of influenza A virus binds to (blank) expressed on many different cells and has a broad host range and tissue tropism.
sialic acid receptors
61
How do enveloped viruses get their genome into a cell?
they fuse their membrane with cellular membranes to deliver the nucleocapsid or genome into the cytoplasm
62
How do most nonenveloped viruses enter the cell?
by receptor mediated endocytosis
63
When will fusion proteins be active?
at neutral pH (plasma membrane-virus fusion) OR In acidic condition of an endosome following receptor mediated endocytosis
64
Can a virus give its genome to a cell with its capsid and envelope?
NO, the capsid and envelope must be removed.
65
Most DNA genomes are delivered to the (Blank), most RNA genomes remain in the (blank)
nucleus cytoplasm
66
Most DNA viruses use the cells (blank) to make mRNA.
DNA-dependent host RNA pol II
67
mRNA must acquire what 2 things?
3' poly A tail and 5' methylated cap
68
Most RNA viruses replicate and produce (blank) in the (blank). Therefore the virus must encode the enzymes for (blank)
mRNA cytoplasm transcription
69
Some complex DNA viruses encode their own (blank) to regulate the expression of viral genes.
transcription factors
70
What delivers the DNA genome to the nucleus?
the nucleocapsid
71
(blank) rely on the cells machinery and substrates for replication
small DNA viruses
72
How do you get the icosahedral shape of the nucleocapsid of a DNA virus?
Capsid proteins migrate into the nucleus, assemble into icosahedral capsids and are filled with the DNA genome
73
How do you get RNA virus replication?
1. binds to cell surface 2. endocytosed, 3. envelope fuses with the endosome vesicle membrane to deliver the nucleocapsid to the cytoplasm. 3. The virion must carry a polymerase, which produces the 5 mRNAs and a full length (+) strand template. 4 Proteins translated, glycoprotein G is glycosylated in the ER processed through the Golgi and delivered to the cell membrane. Genome is replicated from the (+) RNA template and the N, L, NS proteins associate with the genome to form the nucleocapsid The matrix protein associates with the G protein modified membrane which is followed by assembly of the nucleocapsid. The virus buds from the cell in a bullet-shaped virion
74
(blank and blank) constitute the RNA dependent RNA polymerase
L and NS proteins
75
How do you get binding of viral mRNA to host ribosome?
5 cap structure of methylated guanosine mediats binding of mRNA to host ribosome
76
Ribosomes bind to viral mRNA and may produce on large (blank) which needs to be cleaved by cellular or viral proteases.
polyprotein
77
T or F viral mRNA is preferentially translated in many cases
T
78
Viral mRNA is preferentially translated in many cases. Some viruses block cellular mRNA egress from the nucleus T or F
T
79
Some viral proteins require post-translation modifications such as (blank) and (blank)
phosphoryation and glycosylation
80
Viral glycoproteins are synthesize on (blank)
membrane-bound ribosomes
81
What do viral glycoproteins need?
AA sequence to allow for insertion into R
82
Where does viral DNA replication begin? What binds here?
at the origin viral replication factors
83
What do large DNA viruses encode?
their own DNA polymerase which make more errors, creating mutations
84
What are a good target for antiviral nucleotide analogs?
DNA polymerases created by large DNA viruses
85
RNA viruses must encode a (blank) polymerase.
RNA-dependent RNA polymerase
86
What viral RNA strand can initate infection?
(+)
87
What does the positive (+) RNA strand do?
it acts as mRNA and binds to ribosomes and directs protein synthesis
88
What viral RNA strand can initate infection?
(+)
89
What creates (-) negative RNA strand?
RNA dependent RNA polymerase
90
What does (-) strand RNA do?
(-) strand RNA will produce (+) strand RNA which will make mRNA
91
(-) strand RNA viral genomes are the template for production of (blank), this (-) RNA is not infectious unless there is a polymerase is present
(+) mRNA
92
RNA viral transcription and replication occurs in the cytoplasm. What is the one exception?
Influenza viruses
93
Explain RNA virus replication
1. virus binds to cell surface
2. endocytosis of virus
3. nucleocapsid is delivered to cytoplasm
4. Virion polymerase will produce 5 mRNAs and a full length (+) strand
5. Protein translated, glycoprotein G is glycosylated in the ER, processed through the golig and delivered to cell membrane
6. Genome is replicated from the (+) RNA template and N,L,NS proteins assocate with the genome to form the nucleocapsid
7. virus buds from cell in a bullet shaped virion
94
(blank and blank) proteins constitute the RNA dependent RNA polymerase
L and NS proteins
95
Where is glycoprotein G glycosylated, processed and deiivered to?
glycoprotein G is glycosylated in the ER processed through the Golgi and delivered to the cell membrane.
96
What makes up the nucleocapsid?
the N, L, NS proteins associate with the genome to form the nucleocapsid
97
What mediates binding of vira mRNA to host ribosomes?
oThe 5’ cap structure of methylated guanosine mediates binding of viral mRNA to host ribosomes
98
oRibosomes bind to viral mRNA and may produce one large (blank) which needs to be cleaved by cellular or viral proteases
polyprotein
99
oViral mRNA is preferentially translated in many cases. Some viruses block cellular mRNA egress from the nucleus. T or F
T!!!
100
oSome viral proteins require post-translational modifications such as what?
phosphorylation and glycosylation
101
o
oViral glycoproteins are synthesized on (blank) and have the amino acid sequences to allow for (i) insertion into the rough endoplasmic reticulum and (ii) N-linked glycosylation
membrane-bound ribosomes
102
What happens when the concentration of viral structural components is too high?
oWhen the concentration of viral structural components is high enough in the cell then protein-protein, protein-nucleic acid, and protein –membrane interactions occur
103
When does viral budding occur?
after association of the nucleocapsid with the intracellular portion of viral glycoproteins
104
oMost RNA viruses bud from the (blank)
plasma membrane
105
```
=
oOther viruses (the ones that dont bud from plasma membrane) acquire there envelope by budding into the (blank and blank)
```
endoplasmic reticulum and Golgi apparatus
106
Viruses can be released what three ways?
by (i) cell lysis, (ii) exocytosis, or (iii) budding from the plasma membrane
107
oMutated viruses arise from wild-type, which may (i) not change the phenotype, (ii) be detrimental or (iii) enhance pathogenicity and produce drug resistance T or F?
T
108
oMutations in essential genes are (blank) mutations
lethal
109
(blank) mutants cause less serious disease
oAttenuated
110
New virus strains can be produced by (blank) between viruses or the virus and the host (recombination)
intermolecular exchange
111
Viruses with (blank) genomes (influenza) can shuffle there segments if more than one viral strain is present in one host cell (reassortment)
segmented
