Module 9 - Viruses Flashcards
1
Q
What are viruses?
A
Small particles that can replicate inside living host cells
2
Q
How are viruses obligate intracellular parasites?
A
They rely on taking over the host cell to function
3
Q
True or false: viruses can infect all forms of life
A
True
4
Q
How many viruses exist on the planet?
A
Millions
5
Q
How many viruses have been extensively characterized?
A
5000
6
Q
How long have viruses plagues humans?
A
Since before we knew about them
7
Q
How old is the history of virology?
A
Nearly as old as the history of life itself
8
Q
What is virus Latin for?
A
Poison
9
Q
When was yellow fever virus discovered?
A
1901
10
Q
What did Walter Reed do?
A
Showed yellow fever was causes by a virus transmitted by mosquitos in 1901
11
Q
Who discovered yellow fever virus?
A
Walter Reed
12
Q
What did Stanley (from Columbia) do?
A
Crystallized TMV
13
Q
When was TMV crystallized?
A
1935
14
Q
Who crystallized TMB?
A
Stanley (from Columbia)
15
Q
How was TMV isolated?
A
In a filtered, bacteria-free fluid
16
Q
What is the typical size of a virus?
A
10-100 nm
17
Q
What is the typical genome size of a virus?
A
A few thousand to 200,000 nucleotides
18
Q
How many genetic molecules do viruses typically have?
A
One
19
Q
How can viruses have more than one genetic molecule?
A
By having a segmented genome
20
Q
What is the structure of the genetic material in viruses?
A
Linear or circular, single or double stranded DNA or RNA
21
Q
What is the host for poliovirus?
A
Humans
22
Q
What is the structure of poliovirus?
A
Non-enveloped, icosahedral
23
Q
What is the size of poliovirus?
A
30 nm
24
Q
What is the genome size of poliovirus?
A
7.7 kbp
25
What is the genetic material of poliovirus?
ssRNA
26
What is the host for TMV?
Tobacco and related plants
27
What is the structure of TMV?
Non-enveloped, helical
28
What is the size of TMV?
300x18 nm
29
What is the genome size of TMV?
6.4 kbp
30
What is the genetic material of TMV?
ssRNA
31
What does TMV stand for?
Tobacco mosaic virus
32
What is the host of T4?
E. coli
33
What is the structure of T4?
Non-enveloped
34
What is the size of T4?
200x90 nm
35
What is the genome size of T4?
170 kbp
36
What is the genetic material of T4?
dsDNA
37
What is the host for variola virus?
Humans
38
What is the structure of variola virus?
Enveloped, complex
39
What is the size of variola virus?
300x250 nm
40
What is the genome size of variola virus?
186 kbp
41
What is the genetic material of variola virus?
dsDNA
42
What is the most for mimivirus?
Amoeba
43
What is the structure of mimivirus?
Enveloped, complex
44
What is the size of mimivirus?
400 nm
45
What is the genome size of mimivirus?
1200 kbp
46
What is the genetic material of mimivirus?
dsDNA
47
What surrounds the viral genome?
A capsid
48
What is a capsid?
Viral proteins that surround the viral genome
49
What are capsids composed of?
Capsomeres
50
What is a capsomere?
A subunit of a capsid
51
What is a capsomere composed of?
One or more polypeptides
52
What are the common shapes of a capsid?
Helical or icosahedral
53
What type of genome do helical viruses have?
ssRNA
54
What are some examples of helical viruses?
Ebola, TMV
55
What are some examples of icosahedral viruses?
Rhinovirus, adenovirus, poliovirus
56
What does rhinovirus do?
Causes the common cold
57
True or false: capsid shapes are always simple
False: they can have irregular or complex shapes
58
What is the typical structure of bacterial viruses?
Icosahedral head and a helical tail
59
What do the tail fibers do in bacteriophages?
Help binding to host cells
60
What is the nucleocapsid?
The capsid and genome of the virus
61
What is an enveloped virus?
A virus where a plasma membrane surrounds the nucleocapsid
62
What is a naked virus?
A virus where there is no plasma membrane surrounding the nucleocapsid
63
What is another name for a naked virus?
A non-enveloped virus
64
What are some examples of enveloped viruses?
Influenza and HIV
65
What are spikes?
Glycoproteins inserted into the lipid membrane of enveloped viruses
66
What are some examples of spike proteins?
Hemagglutinin and neuraminidase
67
Which virus has hemagglutinin and neuraminidase?
Influenza
68
What does hemagglutinin and neuraminidase determine?
Subtype of influenza
69
What are the 4 steps for viral replication?
1. Adhere
2. Penetrate and uncoat
3. Synthesis
4. Assembly and exit
70
What happens when a virus sticks to the host cell?
It releases its genome into the cell
71
What happens once the viral genome is inside the host cell?
The host cell expresses the genes to make proteins, replicate genome, and put itself together
72
What is the most important part of the viral replication cycle?
Entry into the host cell
73
What does the entry mechanisms depend on?
The host cell
74
How are animal cell viruses different from bacterial, plant, and fungal viruses?
Animal viruses do not have to contend with cell wall, while bacterial, plant, and fungal viruses do
75
What does entry of viruses into plant cells depend on?
Some damage on the plant tissue
76
Why do plant viruses rely on plant tissue damage?
It opens a spot on the cell wall
77
How can plant tissue be damaged?
Through insects feeding on plants, wind damage, hail/rail damage, fire damage, or human-induced damage
78
True or false: bacterial viruses enter the host cell
False: they do not enter the host cell after attachment
79
What happens when bacterial viruses attach to the host cell?
There is a conformational change in the tail protein subunits, which moves DNA from capsid head into bacterial cytoplasm
80
What happens when animal viruses attach to the host cell?
Some form of virion capsid or viral genome enters the cytoplasm
81
How do non-enveloped animal viruses enter the cell?
The entire viral particle enters through endocytosis
82
How do enveloped viruses such as HIV enter the cell?
They undergo a membrane fusion event at the cell surface
83
How do enveloped viruses such as influenza enter the cell?
They first enter through endocytosis, and then the viral capsid undergoes a specific set of disassembly to release the genome into the cytoplasm
84
What is the consequence of viruses only being able to replicate within living host cells (in terms of evolution)?
Their origin must be connected with the host cell
85
What three hypotheses have been proposed for the origin of viruses?
Coevolution, regressive, and progressive
86
What is another name for the coevolution hypothesis?
The virus first hypothesis
87
What does the coevolution hypothesis state?
Viruses co-evolved with current cellular hosts, or existed before cells
88
What are the strengths of the coevolution hypothesis?
It can explain the origin of many RNA viruses
89
What are the weaknesses of the coevolution hypothesis?
It has little support outside of RNA viruses
90
What does the regressive hypothesis state?
Viruses were cells that lost their metabolic and replicative features over time, thus depending on the host cell
91
What are the strengths of the regressive hypothesis?
There is support from nucleocytoplasmic large DNA viruses
92
What are the weaknesses of the regressive hypothesis?
It does not explain the origin of RNA viruses
93
What does the progressive hypothesis state?
Existing genetic elements gradually gained the ability to move between cells
94
What are the strengths of the progressive hypothesis?
There is evidence in the similarity of replication of retroviruses and replication of transposons and retrotransposons
95
Based on the progressive hypothesis, how did retroviruses evolve?
From eukaryal retrotransposons
96
How do transposons move within a genome?
By converting DNA to RNA, and then converting back into DNA
97
How is RNA converted into DNA for transposons?
Through the enzyme reverse transcriptase
98
What is done with the DNA copy produced by reverse transcriptase in transposons?
It can be integrated into a different location on the chromosome
99
How are retroviruses similar to retrotransposons?
They also undergo RNA to DNA conversion, and they have a similar genetic organization
100
True or false: there is evidence for all three hypothesis of viral origin
True: each of them has different evidence
101
True or false: one hypothesis of viral origin completely explains the origin of viruses
False: each of them have a partial description
102
What traits of viruses makes them difficult to work with?
They are small and can only replicate within appropriate host cells
103
What is needed to cultivate viruses?
Host cells must be inoculated with virus, and progeny viruses must be harvested
104
How are bacteriophages cultivated?
A culture of actively growing bacteria are inoculated with a small sample of phage
105
How can a researcher tell that a bacteriophage is replicating?
The growth media changes from turbid to clear
106
What happens after incubation of bacteriophages?
The medium is centrifuged, and the resulting supernatant is filtered
107
What is done to isolate a viral clone?
Molten nutrient agar is added to the cells and poured on a plate
108
What is the purpose of the molten nutrient agar?
It inhibits free movement of virus
109
What does a virus produce when plated?
A visible plaque of dead cells
110
What does each discrete plaque represent?
A clone (the progeny of a single virus)
111
What is done to cultivate animal viruses?
A small amount of virus is added to host cells growing in a flask
112
What do the viruses in the animal cell flask do?
New viral particles are released from infected cells into the medium, and infect other cells
113
What does the replication of many animal viruses lead to?
CPEs
114
What is an example of a virus that produces CPEs?
Poliovirus
115
What does CPE stand for?
Cytopathic effects
116
What are CPEs?
Visible changes in cellular morphology
117
What are CPEs often associated with?
Cell damage or death
118
What are CPEs commonly used as a marker for?
Extent of viral replication
119
What cell line was used to develop the tools to study animal viruses?
HeLa cells
120
What is done for simple and relatively crude purifications?
A viral suspension can be centrifuged and filtered through a very small pore filter
121
What does differential centrifugation do?
Separates particles by mass
122
What does low speed centrifugation lead to?
Pelleting of large objects, including cells
123
What does high speed centrifugation lead to?
Pelleting of small objects, such as viruses
124
What does gradient centrifugation do?
Separates particles by density (concentration)
125
What is the setup for gradient centrifugation?
The sample is layered on top of a density gradient made up of sucrose concentrations (ranging from 20-70%)
126
How does gradient centrifugation work?
During centrifugation, particles move down until they encounter a sucrose concentration equivalent to particle density
127
What is the product of gradient centrifugation?
Bands at different locations in the tube
128
What is the product of differential centrifugation?
Pellets and supernatant
129
What are the 4 methods used to quantify viruses?
Direct count, hemagglutination assay, plaque assay, and endpoint assay
130
How does direct count work?
The absolute number of total viral particles is calculated with an electron microscope
131
What are the disadvantages of the direct count method?
It requires an expensive, specialized microscope, and it does not differentiate between infectious and non-infectious viral particles
132
What does the hemagglutination assay rely on?
The properties of some viruses to stick to RBCs, forming a gel mat
133
What does RBC stand for?
Red blood cell
134
True or false: hemagglutination assay can be done on all viruses
False: it can only be done on certain viruses
135
What is hemagglutionation?
The process of RBCs clumping up together due to viruses binding to the RBC surface
136
True or false: hemagglutination can be seen with the naked eye
True: no microscope is required
137
What are the advantages of the hemagglutination assay?
It is cheap, easy, fast, and requires no microscope
138
What are the disadvantages of the hemagglutination assay?
It cannot differentiate between viable and non-viable viruses, and there is no virus number
139
What type of viruses is the plaque assay useful for?
Phages and plant viruses
140
What is the plaque assay commonly used for?
To determine infectious titer
141
What are the steps of a plaque assay?
1. A series of dishes with host cells are inoculated with serial dilutions of the virus
2. Newly formed viruses infect neighboring cells, resulting in plaques
3. Plaques are counted to determine PFU
142
What is a plaque?
A collection of dead cells
143
What does PFU stand for?
Plaque forming unit
144
What is the endpoint assay used for?
Determining the TCID50
145
What does TCID50 stand for?
Tissue culture infectious dose 50
146
What are the steps of an endpoint assay?
1. Dilutions of viruses are used to infect cells in a growing culture
2. Cells are monitored for CPEs, and calculated to find out how much viruses is needed to cause CPE 50% of the time
147
How is the TCID50 calculated from the endpoint assay?
The number of viruses needed to cause CPE 50% of the time is calculated
148
How can viruses be named?
Based on the location of discovery, the disease they cause, or appearance
149
What are some examples of viruses named based on a location?
Ebola, West Nile
150
What are some examples of viruses named based on diseases?
TMV, Hepatitis A
151
What are some examples of viruses named based on a physical characteristic?
Coronavirus, Picornaviridae
152
What are some notes about Ebola virus?
1. First recognized outbreak occurred in Zaire (Democratic Republic of Congo) near Ebola River
2. Most subsequent outbreaks occurred in central Africa
153
What are some notes about West Nile virus?
1. Initially isolated from a person living near Nile River in Uganda
2. First appeared in USA in 1999, now firmly established in North America
154
What are some notes about TMV?
1. Plant infected show distinct discoloration, or mosaic pattern
2. First described in 1880s, still causes significant crop loss today
155
What are some notes about Hepatitis A virus?
1. A number of viruses (A, B, C) have been identified
| 2. All cause damage to liver cells, but differ significantly from each other
156
What are some notes about coronaviruses?
1. Have projections on surface that resemble crowns or coronas
157
What are some notes about picoronaviruses?
1. Have very small (pico) RNA genomes
158
What does ICTV stand for?
International Committee on Taxonomy of Viruses
159
Based on the ICTV, how are viruses classified?
Based on order, family, subfamily, genus, and species
160
What can be used as a common feature to compare viruses?
How they form mRNA
161
How come mRNA can be used as a common feature to compare viruses?
Because all viruses make mRNA recognized by ribosomes of host cells
162
How does the Baltimore classification system work?
Each virus is divided into 7 classes based on how they make mRNA
163
What did David Baltimore do?
Develop the Baltimore system of classification
164
What is a class I virus?
dsDNA genome
165
What is an example of a class I virus?
Human herpesvirus
166
What is a class II virus?
ssDNA genome
167
What is an example of a class II virus?
Parvoviruses
168
What is a class III virus?
dsRNA genome
169
What is an example of a class III virus?
Reoviruses
170
What is a class IV virus?
ssRNA genome, positive sense
171
What is an example of a class IV virus?
Poliovirus
172
What is a class V virus?
ssRNA genome, negative sense
173
What is an example of a class V virus?
Influenza virus
174
What is a class VI virus?
ssRNA genome, DNA intermediate
175
What is an example of a class VI virus?
HIV
176
What is a class VII virus?
ssRNA genome, RNA intermediate
177
What is an example of a class VII virus?
Hepatitis B virus
178
What class of virus has a dsDNA genome?
Class I
179
What type of virus is human herpesvirus?
Class I
180
What class of virus has a ssDNA genome?
Class II
181
What type of virus is parvovirus?
Class II
182
What class of virus has a dsRNA genome?
Class III
183
What type of virus is reovirus?
Class III
184
What class of virus has a ssRNA genome, positive sense?
Class IV
185
What type of virus is poliovirus?
Class IV
186
What class of virus has a ssRNA genome, negative sense?
Class V
187
What type of virus is influenza?
Class V
188
What class of virus has a ssRNA genome, DNA intermediate?
Class VI
189
What type of virus is HIV?
Class VI
190
What class of virus has a dsDNA genome, RNA intermediate?
Class VII
191
What type of virus is hepatitis B?
Class VII
192
How is electron microscopy used in virology?
It is useful to see physical differences or how they look like
193
How is nucleic acid analysis used in virology?
It provides more exact information about virus identity
194
How is rtPCR different from PCR?
rtPCR uses reverse transcriptase to create cDNA from mRNA, which can then undergo the PCR reaction
195
What is needed for rtPCR?
Primers, Taq polymerase, nucleotides, and reverse transcriptase
196
When were viroids first isolated?
1967
197
How were viroids first discovered?
As infectious agents that caused potatoes to grow abnormally
198
What do viroids do?
Infect plants
199
What is the structure of a viroid?
Naked circular ssRNA, with a complicated secondary structure
200
How do viroids achieve intricate secondary structure?
Through intracellular complementary base pairing
201
How large is a typical viroid?
400 nucleotides
202
What is the purpose of the extensive secondary structure of viroids?
It makes it resistant to ribonucleases
203
What do satellite viruses and satellite RNAs do?
Infect plants
204
What do satellite viruses and satellite RNAs have in common?
They both have small RNA genomes
205
How do satellite viruses and satellite RNAs replicate in hosts?
They require a helper virus that co-infects the host cell for replication
206
Where do satellite viruses get the capsid protein?
From their own gene
207
Where do satellite viruses get the capsid protein?
From the helper virus
208
What is an example of a satellite virus?
HDV
209
What does HDV stand for?
Hepatitis D virus
210
What is needed for HDV to infect a cell?
HBV also needs to infect the cell for HDV to replicate
211
True or false: HDV has an envelope
True: it is an enveloped virus
212
What do prions stand for?
Proteinaceous infectious particles
213
What is the structure of a prion?
Just protein (no DNA or RNA)
214
How are prions infectious agents?
They can replicate in the host and cause diseases
215
What are some specific diseases caused by prions?
Kuru in humans, Scrapie in sheep, mad cow disease in cattle
216
What types of dieases are caused by prions?
TSEs
217
What does TSE stand for?
Transmissible spongiform encephalopathies
218
What are TSEs?
A group of progressive neurological diseases
219
What are prions?
Misshapen forms of naturally occurring proteins
220
Where do the prion proteins normally exist?
On the surface of the neuron
221
What are the two states of the prion protein?
The more common cellular form, or the pathogenic scrapie form
222
What happens when pathogenic proteins come in contact with the normal cellular proteins?
It causes the cellular molecule to change shape and become pathogenic
223
What is the consequence of the prion causing a normal protein to change shape?
It can replicate and function as an infectious agent
224
What can make the prion protein more likely to assume the pathogenic confirmation?
Certain mutations in the gene
225
True or false: prion-associated diseases can be both infectious or genetic
True: it can arise from another source, or from genetics
226
What is thought to lead to disease from prions?
The formation of fibrils
227
How have viruses shaped human history?
Smallpox decimated Native American populations, and influenza influenced the outcome of World War I
228
What did Dimitri Ivanovski do?
Demonstrated a disease in tobacco plants (TMV) that could be transmitted after using a filter in 1892
229
What is the official beginning of virology?
Martinus Beijerinck describing TMV as contagium vivum fluidum (soluble living germ) in 1898
230
What did Frederick Twort and Felix d'Herelle do?
Described bacteriophages in the early twentieth century
231
What does variola virus do?
It is the agent of smallpox
232
What is an example of a virus with a segmented genome?
Influenza virus A
233
How does influenza virus A have a segmented genome?
It has eight segments of ssRNA that code for ten different proteins
234
What are the largest viruses (in terms of size)?
1. Pithovirus sibericum (1.5 um x 500 nm)
| 2. Mimivirus (400 nm)
235
What are the largest viruses (in terms of genome)?
1. Pandoravirus salinus (2.47 Mbp)
2. Megavirus chilensis (1.2 Mbp)
3. Mimivirus (1.2 Mbp)
236
What genes are found in large viruses (such as mimivirus)?
Genes similar to synthesis of nucleotides and amino acids
237
What is the structure of influenza virus?
Multiple copies of the NP (nucleoprotein) and viral polymerase complex associate with each segment of RNA
238
What does helical symmetry lead to?
Filamentous, fiber-like, or rod shaped morphology
239
What is a virion?
Complete viral particle
240
What is the virion in helical plant and bacterial viruses?
The entire helical nucleocapsid
241
What do all known animal viruses with helical symmetry have?
An envelope
242
What does the genome size of a helical virus determine?
How large it is (capsid can grow indefinitely)
243
How come the genome size of an icosahedral virus is limited?
Only a certain amount of genetic material can be packaged inside the capsid
244
What is the purpose of a viral envelope?
The associated proteins are important for successful entry into the cell
245
How many protein units are used for an icosahedral capsid?
60 (3 polypeptides x 20 faces)
246
What is the advantage of a viral envelope?
It can disguise the virus from the host cell immunity, and helps with attachment
247
What is the disadvantage of a viral envelope?
The envelope is typically degraded in external environment through desiccation and exposure to chemicals
248
What is an attachment protein, and what does it do?
It is a protein on the surface of the virus that aids in binding to a host cell
249
How does adenovirus interact with receptors?
A spike protruding from the vertices
250
How does poliovirus interact with receptors?
Through amino acid residues in an indentation within the capsid
251
What receptors does HIV use?
CD4, CCR5, and CXCR4
252
What breaks down the influenza coat when it enters the cell?
Acidic pH
253
How do viruses spread within plants?
Through plasmodesmata
254
True or false: plant viruses recognize specific receptors to enter cells
False: only animal and bacterial viruses do this
255
How can viral particles exit a cell?
Through budding or cell lysis
256
What do respiratory viruses do?
Infect respiratory cells
257
How do respiratory viruses spread?
Through inhalation and exhalation
258
What do enteric viruses do?
Cause intestinal problems by damaging GI tract cells
259
What is an example of an enteric virus?
Rotaviruses
260
How do enteric viruses spread?
Through ingestion (fecal matter)
261
How do blood-borne viruses spread?
Through bodily fluids (blood, semen)
262
What cells does HIV affect?
Immune cells
263
What does NCLDV stand for?
Nucleocytoplasmic large DNA viruses
264
What are some examples of NCLDVs?
Herpesvirus, poxvirus, and mimivirus
265
What hypothesis can be made regarding NCLDVs?
Primordial viruses gave rise to the first eukaryal nucleus
266
What is special about Chlamydia?
It is a bacteria that relies on a host cell for survival
267
What is Chlamydia missing for survival?
An ETC to synthesize ATP
268
What does sequence analysis of viral genomes demonstrate?
Genomes of animal viruses show great similarity to host genomes, and no similarity to bacterial genomes
269
What hypothesis does sequence analysis of viral genomes not support?
The regressive hypothesis
270
How was Mavirus used in the progressive hypothesis?
It has a mechanism similar to transposons
271
What was a major advancement in the field of virology for cultivation?
The development of cell culture techniques
272
What are some examples of CPEs?
The rounding and detachment of the infected cells, or the creation of syncytiums
273
What is a syncytium?
The fusion of individual, infected cells into a large, multinucleated mass
274
What is the problem with filtration?
It does not concentrate the viruses
275
How are the viruses concentrated?
Through ultracentrifugation
276
What is a viral titer?
Concentration of a virus preparation
277
What is the purpose of the latex beads in the direct count?
It is used to determine the exact volume, and thus concentration, of the sample
278
Besides an electron microscope, what can be used to directly count the viruses?
Fluorescent microscopy or flow cytometry
279
What is the purpose of the serial dilutions in the hemagglutination assay?
It can be used to determine the viral titer maximum concentration that still produces complete hemagglutination
280
True or false: hemagglutination can occur without viral particles
True: sometimes the viral proteins alone can induce hemagglutination
281
How come a plaque assay may give a different number than a direct count?
A direct count looks at all particles, while a plaque assay only looks at infectious particles (those that cause cell death)
282
Why may viruses be defective?
They may have been assembled incorrectly, missing part of the genome, or contain mutations to preclude further replication
283
What types of viruses are often quantified by an endpoint assay?
Those that cannot form plaques or cause RBCs to aggregate, but still have an observable effect on cells
284
What does LD50 stand for?
Lethal dose 50
285
What is the LD50?
The amount of virus to kill 50% of the infected animals
286
How come an LD50 is not commonly measured?
It requires the use of a lot of lab animals
287
What is a virus species?
A group whose members share several properties and occupy a common ecological niche
288
What do Paramyxoviridae and Orthomyxoviridae look like under an electron microscope?
Enveloped, spherical, and 100-150 nm in diameter
289
How are Paramyxoviridae and Orthomyxoviridae different?
Paramyxoviridae enter the cell by fusing with the cell membrane, and constain a linear ssRNA genome, while Orthomyxoviridae enter the cell by endocytosis, and have a segmented genome
290
How was an electron microscope helpful and hurtful in the SARS outbreak?
They could identify the virus, but not the specific virus (thought it was paramyxoviridae, not coronavirus)
291
What is an example of a viroid?
PSTVd
292
What does PSTVd stand for?
Potato spindle tuber viroid
293
What is missing from the viroid genome?
Genes that encode for proteins
294
How can viroids replicate?
By using the cell's RNA polymerase
295
How can viroids damage the cell?
By diverting essential resources away from transcription, or interfering with the formation of SRP
296
What does SRP stand for?
Signal recognition particle
297
How does a viroid interact with SRP?
The viroid can bind to 7S RNA, interfering with the formation of SRP
298
What does SRP do?
Directs unfolded polypeptides from the cytoplasm to the ER
299
How can viroids be transmitted between plants?
Through insects or human activities
300
How does HBV help HDV?
HBV provides the proteins necessary for the HDV envelope
301
How are virophages similar to satellite viruses?
They only replicate in host cells coinfected with a helper virus
302
How are virophages different to satellite viruses?
Virophage replication is detrimental to the helper virus
303
When was the first virophage discovered?
2008
304
What is an example of a virophage?
Sputnik
305
How does Sputnik infect a cell?
It replicates in amoeba infected with mamavirus, inhibiting the production of more mamavirus
306
What may virophages be used for?
Lateral transfer of gene material
307
What does CJD stand for?
Creutzfeldt-Jakob disease
308
How do TSEs affect the brain?
They leave sponge-like holes
309
Who first studied prions?
Stanley Prusiner
310
How have viruses been used in research?
They can be used to study the inner workings of cells (DNA replication and gene regulation)
311
What virus was used to study gene regulation?
Simian virus 40 (SV40)
312
How were bacteriophages used in research?
They helped show that DNA, not protein, was the genetic material of cells
313
What did David Baltimore and Howard Temin do?
Discovered reverse transcriptase
314
What did Harold Varmus and J. Michael Bishop do?
Used virology to study cancer in the 1970s
315
Which virus was used to study cancer?
Rous sarcoma virus
316
What is a proto-oncogene?
Genes involved in the normal regulation of the cell cycle
317
What is an oncogene?
Altered forms of proto-oncogenes that can lead to uncontrolled cell growth and development of tumors
318
What are oncolytic viruses?
Viruses that infect and kill cancerous cells without harming normal cells
319
How can reoviruses act as oncolytic viruses?
They preferentially infect cells with activated ras pathways
320
What is gene therapy?
The process of correcting genetic defects in humans
321
How can viruses be used in gene therapy?
They can be used to transport and deliver the gene to the host cells
322
What is nanotechnology?
The development and use of nano-devices
