Chap 13 Flashcards
(285 cards)
1
Q
Can viruses reproduce outside of a living host?
A
No, viruses are obligate cellular parasites, meaning they cannot reproduce outside of a living host
2
Q
Can viruses be cultured outside of hosts?
A
no
3
Q
Viruses can’t be seen with what kind of microscope?
A
light microscope
4
Q
The first human disease associated with a filterable agent was
A
Yellow fever
5
Q
Viruses are mostly made of nucleic acids, either
A
DNA or RNA
6
Q
Capsid
A
protein coat of viruses
7
Q
capsomere
A
building block of a virus’s capsid
8
Q
Some viruses have a lipid bilayer envelope, which they get from
A
host cells upon release
9
Q
Do viruses have ribosomes?
A
No
10
Q
Do viruses have ATP generating mechanisms?
A
no
11
Q
contagium vivum fluidum
A
Fluid with viruses. Couldn’t imagine sub-microscopic organisms
12
Q
What kind of microscope do you need to see a virus?
A
Electron microscope
13
Q
Viruses are inert outside of a host cell, meaning
A
Their nucleic acids are inactive outside of a living host
14
Q
virus
A
submicroscopic, parasitic, filterable agent. Made of nucleic acid surrounding a protein coat.
15
Q
host range
A
spectrum of species, strains or cell types that a pathogen can infect
16
Q
bacteria vs viruses: have a plasma membrane
A
virus: no
typical bacteria: yes
17
Q
bacteria vs viruses: binary fission
A
typical bacteria: yes
virus: no
18
Q
bacteria vs viruses: intracellular parasite
A
typical bacteria: no
virus: yes
19
Q
bacteria vs viruses: pass through bacteriological filters
A
typical bacteria: no
virus: yes
20
Q
bacteria vs viruses: possess both DNA and RNA
A
typical bacteria: yes
virus: no
21
Q
bacteria vs viruses: ATP generating metabolism
A
typical bacteria: yes
virus: no
22
Q
bacteria vs viruses: ribosomes
A
typical bacteria: yes
viruses: no
23
Q
bacteria vs viruses: sensitive to antibiotics
A
typical bacteria: yes
viruses: no
24
Q
bacteria vs viruses: sensitive to interferon
A
typical bacteria: no
viruses: yes
25
Most viruses infect only specific types of ______ in one host
cells
26
Host range of virus is determined by
specific host attachment sites and cellular factors
27
Bacteriophages
viruses that infect bacteria
28
virus size range
Viruses range from 20 to 1000 nm in length
29
How could the small size of viruses has helped researchers detect viruses before the invention of the electron microscope?
since viruses are smaller than bacteria, they could pass through filters designed to trap bacteria, demonstrating the existence of an infectious agent too small to be seen under a light microscope, thus revealing the presence of viruses.
30
Virion
complete, fully developed infectious viral particle
31
Virion is made of
composed of nucleic acid and surrounded by a protein coat outside a host cell
32
how are viruses classified?
by their nucleic acid and by differences in the structures of their coats.
33
How can nucleic acid in viruses vary?
acid-D N A or R N A can be single- or double-stranded; linear or circular
34
Envelope (only found in some viruses) is made of
lipid, protein, and carbohydrate coating on some viruses
35
Spikes
projections from outer surface. made of carbohydrate protein complex.
36
what is the purpose of spikes?
help virus attach to host cell
37
The ability of certain viruses to clump red blood cells is associated with
spikes
38
How do viruses cause hemagglutination?
Such viruses bind to red blood cells and form bridges between them.
39
nonenveloped viruses
Viruses whose capsids aren’t covered by an envelope
40
The capsid of a nonenveloped virus protects the nucleic acid from
nuclease enzymes in biological fluids and promotes the virus’s attachment to susceptible host cell.
41
Viruses may be classified into several different morphological types on the basis of
Their capsid architecture
42
The structure of these capsids has been revealed by electron microscopy and a technique called
X-ray crystallography.
43
Helical viruses resemble
long rods that may be rigid or flexible
hollow, cylindrical capsid
44
Polyhedral viruses
many sided
45
within helical viruses, the viral nucleic acid is found within
a hollow, cylindrical capsid that has a helical structure
46
Examples of diseases caused by helical viruses
viruses that cause rabies and Ebola are helical viruses.
47
The capsid of most polyhedral viruses is in the shape of an
icosahedron, a regular polyhedron with 20 triangular faces and 12 corners
48
The capsomeres of each face of an icosahedron form an
equilateral triangle
49
adenovirus and poliovirus
icosahedral polyhedral viruses
50
Enveloped viruses
the capsid of some viruses is covered by an envelope.
51
Enveloped viruses shape
roughly spherical
52
When helical or polyhedral viruses are enclosed by envelopes, they are called
enveloped helical or enveloped polyhedral viruses
53
An example of an enveloped helical virus is the
influenza virus
54
An example of an enveloped polyhedral (icosahedral) virus is
the human herpes virus
55
Virus with complicated structure, such as
a bacteriophage
56
Some bacteriophages have capsids to which
additional structures are attached.
57
poxviruses
complex viruses
58
don’t contain clearly identifiable capsids but do have
several coats around the nucleic acid
59
bacteriophages are what kind of virus?
complex
60
Genus names end in
-virus
61
Family names end in
-viridae
62
Order names end in
-ales
63
Viral species
a group of viruses sharing the same genetic information and ecological niche (host)
64
Descriptive common names are used for
species
65
Subspecies are designated by a
number
66
How does a virus species differ from a bacterial species?
Bacteria are single cells that can survive on their own, inside or outside the body. Viruses cause infections by entering and multiplying inside the host's healthy cells
67
Viruses must be grown in
living cells
68
Bacteriophages are grown in
bacteria
69
What forms plaques?
Bacteriophages
70
Plaques
clearings on a lawn of bacteria on the surface of the agar
71
Plaque forming units
Each plaque corresponds to a single virus
72
Specific epithets for viruses aren't used t/f?
true, Viral species is designated by descriptive common names.
73
Why does most understanding of viruses come from bacteriophages?
because bacteriophages grow in bacterial cultures
74
plaque method
Detects infectious viruses in concentrates in 3-5 days by culturing cells where plaques form
method used for detecting infectious viruses in concentrates by culturing cells, where plaques develop after 3-5 days to indicate the presence of viruses.
75
How does the plaque method work?
1. A bacteriophage sample is mixed with host bacteria and melted agar.
2. The agar containing the bacteriophages and host bacteria is then poured into a Petri plate containing a hardened layer of agar growth medium
3. The virus-bacteria mixture solidifies into a thin top layer that contains a layer of bacteria approximately one cell thick. Each virus infects a bacterium, multiplies, and releases several hundred new viruses. These newly produced viruses infect other bacteria in the immediate vicinity, and more new viruses are produced.
4. all the bacteria in the area surrounding the original virus are destroyed. This produces a number of clearings, or plaques,
76
What is a plaque-forming unit?
visible clearing in bacterial culture caused by lysis of bacterial cells by bacteriophages
77
how do you culture animal viruses in a lab?
using living animals, embryonated eggs, or cell cultures.
78
Most experiments to study the immune system’s response to viral infections must also be performed in
virally infected live animals.
79
diagnostic procedure for identifying and isolating a virus from a clinical specimen
Animal inoculation; After the animal is inoculated with the specimen, the animal is observed for signs of disease or is killed so that infected tissues can be examined for the virus.
80
The lack of natural animal models for AIDS has slowed our understanding because
slowed our understanding of its disease process and prevented experimentation with drugs that inhibit growth of the virus in vivo
81
How are viruses cultured in embryonated eggs?
Virus injected into the egg
Viral growth is signaled by changes or death of the embryo
82
have replaced embryonated eggs as the preferred type of growth medium for many viruses.
cell cultures
83
Cell culture lines are started by
treating a slice of animal tissue with enzymes that separate the individual cells.
84
Normal cells tend to adhere to the glass or plastic container and reproduce to form a monolayer, but viruses infecting such a monolayer sometimes cause
the cells of the monolayer to deteriorate as they multiply.
85
cytopathic effect
cell deterioration; A visible effect on a host cell, caused by a virus, that may result in host cell damage or death.
86
Virally infected cells are detected via their
deterioration, known as the cytopathic effect (C P E)
87
CPE can be detected and counted in much the same way as plaques caused by bacteriophages on a lawn of bacteria and reported as
PFU/ml
88
Viruses may be grown in _________ or ___________ cell lines
primary or continuous cell lines
89
Primary cell lines
Human tissue cells that grow for only a few generations in vitro.
90
widely used for culturing viruses that require a human host.
diploid cell lines
91
developed from human embryos can be maintained for about 100 generations
diploid cell lines
92
diploid cell lines
eukaryotic cells grown in vitro
93
used to culture rabies virus for a rabies vaccine called human diploid culture vaccine
Cell lines developed from embryonic human cells
94
continuous cell line
Animal cells that can be maintained through an indefinite number of generations in vitro
95
Which cell lines are used when viruses are routinely grown in a laboratory?
continuous cell lines
96
transformed (cancerous) cells that can be maintained through an indefinite number of generations, and they’re sometimes called immortal cell lines
continuous cell lines
97
steps for growing transformed cells
1. Tissue is treated with enzymes to separate the cells
2. Cells are suspended in a culture medium
3. Normal or primary cells grow in a monolayer across the glass or plastic container. Transformed cells or continuous cell cultures do not grow in a monolayer
98
How are viruses identified?
1. Cytopathic effects
2. Serological tests
3. Nucleic acids
99
Western blotting serological test
reaction of the virus with antibodies
100
RFLPs
molecular method that helps identify and characterize viruses. restriction fragment length polymorphisms
101
identification methods based on nucleic acids?
RFLPs
PCR
102
PCR polymerase chain reaction
allows specific identification of the infective agents and the detection of multiple/co-infecting viruses.
103
Western blotting
A technique that uses antibodies to detect the presence of specific proteins separated by electrophoresis.
104
For a virus to multiply it must
1. invade a host cell
2. take over the host’s metabolic machinery
105
The multiplication of viruses can be demonstrated with a
one-step growth curve
106
The data are obtained by
infecting every cell in a culture and then testing the culture medium and cells for virions and viral proteins and nucleic acids.
107
Eclipse period of one step growth curve
The time during viral multiplication when complete, infective virions are not present.
108
No new infective virions are found in a culture until after
biosynthesis and maturation have taken place.
109
What happens to most infected cells as a result of infection?
cells die as result of infection, consequently, new virions won't be produced.
110
Phage causes lysis and death of the host cell
Lytic cycle
111
Lytic cycle
mechanism of phage mutation that results in host cell lysis
112
Lytic cycle ends with
the lysis and death of the host cell
113
host remains alive
lysogenic cycle
114
lysogenic cycle
Stages in viral development that result in the incorporation of viral DNA into host DNA
115
Bacteriophages can multiply by two mechanisms
the lytic cycle or the lysogenic cycle
116
The virions of _______ bacteriophages are large, complex, and nonenveloped, with a characteristic head-and-tail structure
T-even
117
Lytic cycle phases
1.attachment,
2. penetration,
3.biosynthesis,
4. maturation,
5. release.
118
Attachment
Phage attaches to host cell
119
Penetration
Phage penetrates host cell and injects its DNA
120
Biosynthesis:
Phage DNA directs synthesis of viral components by the host cell.
121
Maturation
Viral components are assembled into virions
122
Release
host cell lyses and new virions are released
123
Phage conversion
Genetic change in the host cell resulting from infection by a bacteriophage. the host cell exhibits new properties
124
Specialized transduction
process of transferring a piece of cell DNA adjacaent to a prophage to another cell
125
specialized transduction is initiated during
the lysogenic cycle of temperate bacteriophages
126
virulent bacteriophages reproduction
carry out lytic cycle
127
temperate bacteriophages replication
carry out two types of life cycle: lytic and lysogenic
128
In temperate bacteriophages, after penetration, the phage DNA forms a
circle
129
The circle of DNA can then
replicate and be transcribed to produce phage components in the lytic cycle, OR can proceed to the lysogenic stage.
130
During the biosynthesis stage of the lytic cycle in temperate bacteriophages,
the phage DNA directs the host cell to make viral components
131
after penetration, in the lysogenic cycle, the phage DNA integrates within bacterial chromosome by
recombination
132
The inserted phage DNA is called a
Prophage
133
Most of the phage proteins are repressed by
two repressor proteins that are products of phage genes
134
After combining the DNA, what happens when the bacteria reproduces?
the prophage is also copied
135
induction
The prophage is excised from the host chromosome.
136
What causes induction?
can occur spontaneously through recombination, or some other genetic event, UV light, or chemicals
137
after induction, the phage may enter the
lytic cycle
138
phage attaches by the tail fibers to the host cell
attachment
139
phage lysozyme opens the cell wall; tail sheath contracts to force the tail core and D N A into the cell
Penetration
140
production of phage D N A and protein
biosynthesis
141
assembly of phage particles
Maturation
142
phage lysozyme breaks the cell wall
Release
143
Lysogeny
A state in which phage DNA is incorporated into the host cell without lysis. phage remains latent
144
In contrast to T-even bacteriophages, some viruses don’t cause lysis and death of the host cell when they multiply.
lysogenic/temperate phages
145
Steps of lysogenic cycle of bacteriophage I in E. Coli
1. Phage attaches to host cell and injects DNA
2. Phage DNA makes a circle
3. can enter lytic cycle, where circle multiplies and gets transcribed OR
3.bcircle recombines with bacterial DNA and gets replicated every time bacteria divides. Prophage DNA remains latent
4. phage DNA can be ejected and start lytic cycel
146
lysogenic cells are immune to reinfection by
the same phage. However, the host cell isn’t immune to infection by other phage type
147
host cell may exhibit new properties caused by
phage conversion
148
generalized transduction
Bacterial genes can be picked up in a phage coat and transferred to another bacterium
149
possible results of lysogeny
1. Specialized transduction
2. immunity to reinfection by same phage
3. Phage conversion
150
specialized transduction
process of transferring a piece of cell DNA adjacent to a prophage to another cell. packages bacterial DNA along with its own DNA. When viral dna leaves, it carries some of the genes from one bacterium to another.
151
Specific bacterial genes transferred to another bacterium via a phage. The becaterial genes next to the phage
Changes genetic properties of the bacteria
specialized transduction
152
Two types of transduction
generalized and specialized
153
Generalized transduction is initiated during
the lytic cycle of virulent bacteriophage
154
The donor DNA for generalized transduction can be
any fragment of the bacterial chromosome
155
Transduction
DNA from one cell is transferred to another cell via a replicating virus
156
Specialized transduction is initiated during the
lysogenic cycle of a temperate bacteriophage.
157
Donor DNA for specialized transduction is
a very specific part of the bacterial chromosome adjacent to the prophage
158
Transducing phages
made of phage and bacterial DNA, when injected the bacterial DNA also spreads to host.
159
The multiplication of animal viruses follows the basic pattern of bacteriophage multiplication but has several __________,
differences
160
Animal viruses differ from phages in their mechanism of
entering the host cell
161
Regarding animal viruses, once the virus is inside, the synthesis and assembly of the new viral components are somewhat _________
different because of diffences in prokaryotic and eukaryotic cells
162
______ ________may have certain types of enzymes not found in phages
Animal viruses
163
Finally, the mechanisms of maturation and release, and the effects on the host cell, differ in
animal viruses and phages
164
Multiplication of Animal Viruses attachment
viruses attach to the cell membrane
165
Multiplication of Animal Viruses entry by
receptor-mediated endocytosis or fusion
166
do animal viruses require uncoating?
yes, enzymatic removal of capsid proteins happens
167
Biosynthesis of animal viruses happens in
nucleus (DNA viruses) or cytoplasm (RNA viruses)
168
Infection by animal viruses is latent, meaning
slow viral infections; cancer
169
How are animal viruses released?
Enveloped viruses bud out; nonenveloped viruses rupture plasma membrane.
170
Animal viruses require uncoating, meaning
viral or host enzymes break down protein coat
171
Biosynthesis of animal viruses
production of nucleic acid and proteins
172
Maturation of animal viruses
nucleic acid and capsid proteins assemble
173
Animal viruses release by:
budding (enveloped viruses) or rupture
174
naked viruses
Animal viruses without an envelope. Bind to surface of host cell and inject dna similar to bacteriophages.
175
Some enveloped animal viruses infect the host cell by binding to receptors on the host cell
The viral envelope merges with the host cell membrane and the capsid enters the cell . After entry, the capsid opens and releases the viral genetic material into cytoplasm.
176
Upon attachment, some enveloped viruses infect the host cell via inducing
phaogytocis.
177
When the virus has entered the cell, the outer and inner part of the envelope
merge together and the capsid is released into the cytoplasm
178
The type of nucleic acid in an animal virus determines how the viral nucleic acid and proteins are synthesized.
true
179
When the single stranded DNA genome of a parvovirus enters a host cell and invades its nucleus a complementary strand is
produced
180
the complementary strand is replicated
normally
181
mRNA is transcribed and transported into
Cytoplasm
182
viral capsomere proteins are produced in
cytoplasm
183
capsomere protein enter the
nucleus of the host , and the virions containing the original single stranded RNA are assembled
184
Virus dsDNA synthesis
two strands, same process and single strand DNA virus
185
186
synthesis of viruses with single strand RNA genome +RNA
1. can act directly as mRNA AKA as sense strand
187
Sense strand
read by host ribosomes to make viral proteins
188
Virus with +RNA carries a unique polymerase
polymerase makes a complimentary negative strand. also called an antisense strand.
189
There is no known animal equivalent of the rna dependent
polymerase
190
the negative strand RNA can act as a template for
positive strand RNA
191
positive strand single strand RNA viruses are assembled in the cytoplasm of the
host cell after the viral capsomere proteins have been produced.
192
viruses with single strand negative sense RNA -RNA are in a special situation
their RNA will not act as messenger RNA until its transcribedd into the sense strand. carries its own rna polymerase to make positive strand.
193
When -RNA is packages into virions it must contain
RNA POLYMERASE and -RNA
194
dsRNA
sense strand acts as mRNA for protein production. two strands get packaged along with a polymerase.
195
retrovirus
special kind of +RNA virus.
196
When a retrovirus infects a cell, its +RNA strand is transcribed into a
-DNA strand
197
wat does retrovirus use to make -DNA
viral reverse transcriptase
198
-DNA IS transcribed into
double stranded DNA, WHICH SERVES AS A TEMPLATE FOR THE VIRAL RNA genome
199
positive strand RNA serves as
template for viral protein syntheis. Reverse transcriptase is packaged in virion
200
Which viruses generally leave their host cells?
naked; by accumulating until cell lyses. Causes inflammation and infection in tissues
201
Enveloped viruses leave by
merging with one of the cell's membranes, the nuclear membrane , the endoplasmic reticulum membrane, or the cytoplasmic membrane
202
during synthesis, some viral glycoproteins are embedded in cellular membrane
act as recognition sites for viral capsid.
203
How do enveloped viruses leave the host?
bud off thanks to glycoproteins. cell membrane forma a bud which pinches off and make an envelope
204
Advantage of enveloped viruses
does not need cell to lyse, so the cell can stay alive longer and make more copies
205
D N A viruses replicate their D N A in
the nucleus of the host using viral enzymes
206
DNA VIRUSES SYNTHESIZE CAPSID IN THE CYTOPLASM USING
HOST CELL ENZYMES
207
Adenoviridae
DDN, respiratory infection humans, tumors animals
Double-stranded D N A, nonenveloped
Respiratory infections in humans
Tumors in animals
208
Poxviridae
DDE skin lesions
Double-stranded D N A, enveloped
Cause skin lesions
209
Vaccinia and smallpox viruses (Orthopoxvirus)
Poxviridae
210
Herpesviridae
DDE
Double-stranded D N A, enveloped
211
H H V-1 and H H V-2-Simplexvirus
Cause cold sores
212
H H V-3-Varicellovirus
causes chickenpox
213
H H V-4-Lymphocryptovirus
causes mononucleosis
214
H H V-5-Cytomegalovirus
H H V-6 and H H V-7-Roseolovirus
are types of
herpesviridae
215
H H V-8-Rhadinovirus
causes Kaposi’s sarcoma
216
Papovaviridae
DDN
Double-stranded D N A, nonenveloped
217
Papillomavirus leads to
warts
218
Hepadnaviridae
DDE
Double-stranded D N A, enveloped
Hepatitis B virus
Use reverse transcriptase to make D N A from R N A
219
Virus multiplies in the host cell’s cytoplasm using
R N A-dependent R N A polymerase
220
ss R N A; + (sense) strand
Viral R N A serves as m R N A for protein synthesis
221
ss R N A; − (antisense) strand
Viral R N A is transcribed to a + strand to serve as m R N A for protein synthesis
222
ds R N A
double stranded RNA
223
Picornaviridae
SRN+
Single-stranded R N A, + strand, nonenveloped
224
Enterovirus
Poliovirus and coxsackievirus
Rhinovirus
hepatitis A virus
Types of picornaviridae
225
Rhinovirus
common cold
226
Togaviridae
SRE+
Single-stranded R N A, + strand, enveloped
227
Alphavirus
(Togaviridae)
Transmitted by arthropods; includes chikungunya
228
Rubivirus (togaviridae)
Rubella
229
Rhabdoviridae
SR-, numerous animal diseases
Single-stranded R N A,
, -Strand, one RNA strand
numerous animal diseases
230
Lyssavirus
rabies (Rhabdoviridae)
231
Reoviridae
DRN
Double-stranded R N A, nonenveloped
232
Reovirus (Reoviridae)
(respiratory enteric orphan)
233
Rotavirus leads to (Reoviridae)
(mild respiratory infections and gastroenteritis)
234
Use reverse transcriptase to produce D N A from the viral genome
ssRNA
Single stranded RNA , produce DNA
235
Viral D N A integrates into the host chromosome as a
provirus
236
Retroviridae examples
Lentivirus (H I V)
Oncoviruses
237
Several types of cancer are caused by
viruses
238
Cancer may develop a long time after
viral infection
239
Cancers caused by viruses are not
contagious
240
241
Sarcoma
cancer of connective tissues
242
Adenocarcinoma
cancers of glandular epithelial tissue
243
oncogenes
transform normal cells into cancerous cells
244
Oncogenic viruses
become integrated into the host cell’s D N A and induce tumors
245
A transformed cell harbors a ______ on the surface
Tumor-specific transplantation antigen
246
A transformed cell harbors a ______ in the nucleus
T antigen
247
Adenoviridae
Herpesviridae
-Epstein-Barr virus
Poxviridae
Papovaviridae
-Human papillomavirus
Hepadnaviridae
-Hepatitis B virus
DNA oncogenic viruses
248
How is retroviridae oncogenic?
viral R N A is transcribed to D N A (using reverse transcriptase), which can integrate into host D N A
249
H T L V-1 and H T L V-2 cause
adult T cell leukemia and lymphoma
250
Latent virus remains in asymptomatic host cell for
long periods
251
A latent virus may reactivate due to
changes in immunity
252
Examples of things that happen thanks to latent viral infections
Cold sores,
shingles
253
persistent viral infection
occurs gradually over a long period; is generally fatal
254
Example of a persistent viral infection
Subacute sclerosing panencephalitis (measles virus)
255
viruses continuously released
persistent infection
256
13-13, 13-14 Is shingles a persistent or latent infection?
latent
257
Plant viruses enter through
wounds or via insects
258
Plant cells are generally protected from disease by an
inpermeable cell wall
259
Viroids:
short pieces of naked RNA
260
Cause potato spindle tuber disease
viroids
261
virusoids
viroids enclosed in a protein coat
262
Virusoids only cause disease when
plant cell is coinfected with a virus
263
Caulimoviridae characteristics
DDN
Double-stranded DNA, nonenveloped
264
Caulimoviridae viral genus or unclassified members
Cauliflower mosaic virus
265
Prions
Proteinaceous infectious particles
266
Prions Inherited and transmissible by
ingestion, transplant, and surgical instruments
267
Spongiform encephalopathies
neurological diseases caused by large vacuoles in the brain
268
Examples of Spongiform encephalopathies
“Mad cow disease”
Creutzfeldt-Jakob disease (C J D)
Gerstmann-Sträussler-Scheinker syndrome
Fatal familial insomnia
Sheep scrapie
269
PrPC
normal cellular prion protein, on the cell surface
270
PrPSc
scrapie protein; accumulates in brain cells,
accumulates in bran cells forming plaques
271
How do prions cause illness
They make other cellular proteins misfold into infectious forms
272
All mammalian cells contain a gene that codes for the primary sequence of aminoacids for the prion protein
PrP
273
Normally, Prp FOLDS INTO A functional form with a-helices called
cellular PrP
274
What is the normal function of the prion protein?
not well understood, but important in synaptic development and function
275
may be involved in stabilizing structure of synapses and establishing memory
PrP
276
Is also capable of folding into a from with beta pleated sheets
PrP
277
Do not reproduce like bacteria or viruses
Prions; they make normal prions into infectious prions, by folding into beta pleated sheets.
278
Number of infectious prions is increased by
conversion instead of reproduction
279
The number of infectious prions has increased by
conversion instead of reproduction
280
Multimers
infectious conformation . Very stable and resistant to protease.
281
probably lead to damage in prion infected tissues
multimers
282
Creutzfeld Jakob disease
1/1000000 people, appears in mid life20-70 age, avg age of onset 50 , affectscerebrum
283
Can transform cells and cause cancer
Papillomavirus
284
Double stranded DNA serves as
TEMPLATE FOR THE VIRAL RNA genome
285
Hepadnaviridae uses reverse transcriptase to make
(Hepatitis B virus )
D N A from R N A
