Lecture 10 Viruses General Characteristics Flashcards
(120 cards)
1
Q
What type of genetic information are in viruses?
A
DNA or RNA
2
Q
What is the genetic information in viruses contained in?
A
Protective protein coat
3
Q
Inert particles
A
no metabolism, replication, motility
4
Q
Genome hijacks host cell’s _____
A
replication machinery
5
Q
Are viruses organisms?
A
No
6
Q
What do viruses require?
A
live organism as host
7
Q
Can viruses be grown in pure culture?
A
No
8
Q
Which microscope are viruses NOT seen in
A
Light microscopy
9
Q
Viruses that infect bacteria are called
A
bacteriophages
10
Q
viruses are vehicles for what
A
horizontal gene transfer
11
Q
what is virion
A
nucleic acid
12
Q
What is virion surrounded by
A
capsid (protein coat)
13
Q
Capsid is composed of what
A
Capsomeres
14
Q
What are nucleocapsid
A
Capsid plus nucleic acids
15
Q
What is nucleic acid
A
Either DNA or RNA, may be singular stranded or double stranded
16
Q
_____ viruses are surrounded by lipid bilayer obtained from host cell
A
Enveloped
17
Q
Enveloped viruses are surrounded by what layer
A
Lipid bilayer obtained from host cell
18
Q
_____ is between nucleocapsid envelope
A
Matrix protein
19
Q
How is non-enveloped viruses different from enveloped viruses?
A
More resistant to disinfectants
20
Q
_____ are attached to receptor sites on host cells
A
Spikes
21
Q
Phages attach by _____
A
Tail fibers
22
Q
Spikes attach to _____ sites on host cells
A
Receptor
23
Q
What are the three shapes of viruses
A
Icosahedral, helical, complex
24
Q
What is an example of icosahedral
A
20 flat triangles
25
What is an example of helical
Capsomeres arranged in helix
26
What is example of complex
phage, icosahedral nuceleocapsid, helical protein
27
What type of virus is papillomaviridae
type of DNA, outer covering
double stranded DNA, non-enveloped
disease= human papillomavirus
28
What type of virus is herpesviridae
type of DNA, outer covering
Double stranded DNA, enveloped
disease=herpes zoster virus, herpes simplex virus
29
What type of virus is Reoviridae
type of DNA, outer covering
double stranded, non-enveloped, human rotavirus
30
What type of virus is Picornaviridae
type of DNA, outer covering
Single stranded (plus strand), non-enveloped
poliovirus, rhinovirus, hepatitis A
31
What type of virus is Caliciviridae
type of DNA, outer covering
Single stranded (plus strand), non-enveloped, norovirus
32
What type of virus is coronaviridae
type of DNA, outer covering
single stranded (plus strand), enveloped
SARS, MERS
33
What type of virus is Rhabdovirus
type of DNA, outer covering
single stranded (minus strand), enveloped, rabies
34
What type of virus is Paramyxoviridae
type of DNA, outer covering
Single stranded (minus strand), enveloped, influenza virus
35
What type of virus is hepadnaviridae
type of DNA, outer covering
DNA, enveloped, hepatitis B
36
What type of virus is Retrovirus
type of DNA, outer covering
RNA, enveloped, human immunodeficiency virus (AIDS)
37
What are viruses that are oral-fecal route called
Enteric viruses
38
What are respiratory route called
Respiratory virus
39
what is arboviruses
spread by arthropods, often can infect widely different speices
40
What are the three types of bacteriophages
Lytic, temperate, filamentous
41
What is latent state
Viral genome remains silent, but is replicated along the host cell genome
42
What is productive infection
New viral particles produced
43
Lytic phages exit the host by _________ the cell
Lysing
44
What type of infection is lytic phages
Productive infection
45
What are the 5 steps of lytic phase
Attachment
genome entry
synthesis
assembly
release
46
What happens in attachment phase of lytic phage
phage attaches to receptors
47
What happens in genome entry phase of lytic phage
T4 lysoszyme degrades cell wall, tail contracts, injects though cell wall, capsid remains OUTSIDE cell
48
What happens in synthesis phase of lytic phage?
Synthesis of phage proteins and genome
49
What happens in assembly stage of lytic phage
some components assemble spontaneously, others require protein scaffolds
50
What happens in the release stage of lytic phage
lysozyme produced late in infection, digests cell wall, cell lyses, releases phage
51
_________ phages can direct a lytic infection or incorporate DNA into host cell genome
Temperate phages
52
In temperate phage infections, infected cell is _________
Lysogen
53
In temperate phage infections, integrated phage DNA is _________
prophage
54
What is the model of temperate phage in temperate phage infections
Lambda
55
in temperate phages, _________ inserts phage DNA at site on chromosome
integrase
56
_________ replicates along with host chromosome in temperate phage infections
prophage
57
_________ prevents excision, maintains lysogenic state
temperate phage infections
Repressor
58
if DNA is damaged, SOS repair system turns on, actives _________
Protease
59
What is phage induction
Protease destroys repressor, allows prophage to be excised, enter lytic cycle
allows phage escape damaged host
60
Lysogen is immune to
Superinfection
61
What is superinfection
Infection by the same phage
62
What is lysogenic conversion
Lysogen may show change in phenotype due to prophate DNA
63
toxics are encoded by phage genes, only strains carrying _________ produce toxins
Prophage
64
What are filamentous phages
Single stranded DNA phages, looks like long fibers
65
What infections do filamentous phages cause
Productive infections
- host cells not killed but grow slowly
66
What is model for filamentous phage
M13 phage
67
in filamentous phages, _________ synthesizes complementary strand
DNA polymerase
68
What is replicative form of filamentous phage
one strand used as template for synthesis of mRNA copies of genome
69
in filamentous phages, M13 particles assembled in process of _________
Extrusion
70
What is generalized transfuction
packaging error during phage assembly, some phages degrade host chromosome, fragments can be mistakenly packed into phage head
71
Phages that go thru generalized transduction can't direct _________
phage replication cycle
72
What are phages that can't do phage replication cycle because of generalized transduction called
Transducing particles
73
What happens to transducing particles after they're released
bind to new host, inject DNA
74
DNA may integrate via _________ for transducing particles
Homologous recombination
75
What is specialized transduction
excision mistake during transition from lysogenic to lytic cycle of temperate phage
76
In specialized transduction, what is removed?
short piece of bacterial DNA
77
What happens to excised DNA from specialized transduction?
goes into phage head, defective particles released
78
What can the excised DNA do?
Can bind to new host, inject DNA
79
What genes are transferred in specialized transduction?
only bacterial genes adjacent to integrated phage DNA
80
Viruses only multiply inside _________
living cells
81
What are plaque assays used to count
phage particles in samples like sewage, seawater, soil
82
In plaque assays, zones of clearing from bacterial lysis are _________
Plaques
83
plaque forming unit represent_________
single phage
84
Counting plaques yields the _________
Titer
85
What is titer
Concentration of phage in original sample
86
First step of animal virus replication
attachment
87
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
host cell surface
cell types and tissues
88
2. penetration and uncoating - animal virus replication
- enveloped viruses enter by _________ or _________
- _________ virus cannot fuse
- entire _________ enters cell, nucleic acid separates from protein coating
fusion, endocytosis
non-enveloped
virion
89
3. 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
genes
polyprotein, protease
90
Three replication strategies depending on what three viruses
DNA virus, RNA virus, reverse transcribing virus
91
double stranded DNA is _________ to form viral genome
replicated
92
The negative strand of double stranded DNA is transcribed to produce _________
translated to make _________
mRNA
viral proteins
93
how is single stranded DNA replicated?
Complement to DNA synthesized FIRST, acts as template to produce more copies of viral genome
94
in single stranded DNA replication, the _________ strand is transcribed to produced mRNA
Negative
95
What kind of stranded are RNA viruses
single stranded
96
Where do RNA viruses replicate?
cytoplasm
97
RNA viruses require what enzyme
RNA-dependent RNA polymerase (replicase)
98
What does the RNA-Dependent RNA polymerase do?
Allows use of RNA template to make new strand of RNA
99
What genome serves as mRNA
+ ssRNA
100
What genome is complement to RNA
- ssRNA
101
What genome contains both mRNA and complement to mRNA
+/- dsRNA
102
Replication of + ssRNA virus
- viral RNA binds to _________, produces viral replicase
- viral replicase produces multiple copies of _________
Ribosome
complementary (-)
103
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
complementary +
+ RNA strand
complementary - RNA
104
What MUST happen in the replication of - ssRNA virus?
replicase must accompany virus since first step is to make + strand
105
Replication of dsRNA virus
- _________ enters host cell with dsRNA
- replicase uses _________ strand to produce _________ strand
- _________ strand can serve as mRNA
replicase
- RNA strand to produce + RNA strand
+ RNA strand
106
Replication of RNA viruses
Replicase lacks _________ ability
- generates _________ during replication
- results in _________
proofreading
mutations
Antigenic drift
107
In replication of RNA viruses, some RNA viruses have _________ genomes
segmented
108
What is subtype of segmented genomes in RNA viruses?
antigenic shift
109
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
reverse transcriptase
retroviruses
Complementary
110
spontaneous self-assembly when viral _________ and _________ accumulate in host cell
nucleic acid and capsid proteins
111
Most enveloped viruses leave via _________
budding
112
Viral _________ insert into host cell membrane, matrix proteins accumulate; nucleoacapsids extruded
protein spikes
113
Non-enveloped viruses released when host cell dies by _________ initiated by virus or host
apoptosis
114
how many low-pathogenicity coronaviruses are endemic in humans?
4
115
how many coronaviruses have crossed the species barrier since 2000?
Three
116
What protein protrudes from the viral surface and resembles a crown?
S protein
117
SARS-CoV-2 belongs to what genus?
B-coronavirus, coronaviridae
118
SARS-CoV-2 is an enveloped or non-enveloped vrius?
Enveloped
119
SARS-CoV-2 is what type of genome?
single stranded, unsegmented, +
120
What are the 4 proteins in SARS-CoV-2
Spike glycoproteins
Envelope glycoproteins
membrane glycoproteins
nucleocapsid protines
