Test 3 Flashcards
(328 cards)
1
Q
Virus
A
Genetic element that cannot replicate independently of a living host cell
2
Q
What is a virus made of
A
Nucleic acid surrounded by protein (viral genome and protein coat)
3
Q
Virus particle name
A
Virion
4
Q
Virion
A
Extracellular form of a virus. Exists outside the host and facilitates transmission from one host cell to another
5
Q
Other layers that could make up a virus
A
Envelope
6
Q
When do viruses replicate and reproduce
A
Upon infection (entering host)
7
Q
True or false, viruses have a metabolism
A
False
8
Q
Classification of viruses
A
Obligate parasites
9
Q
Capsid
A
Protein shell that surrounds the genome of a virus particle
10
Q
Viruses with no other layers
A
Naked
11
Q
Bacterial viruses name
A
Phage
12
Q
Phage
A
Only infects bacteria, harmless to humans
13
Q
envelope viruses consist of
A
Phospholipid bilayer (from host cell membrane) and viral proteins
14
Q
Nucleocapsid
A
Nucleic acid and protein
15
Q
What is the capsid composed of
A
Capsomeres
16
Q
Virulent (lytic) infection
A
Replicates and destroys host
17
Q
Lysogenic infection
A
Host cell genetically altered because viral genome becomes part of the host genome
18
Q
True or false, viral genomes can be DNA or RNA
A
True
19
Q
True or false, viral genomes can be single or double stranded
A
True
20
Q
Types of single stranded
A
Plus sense and minus sense
21
Q
Plus sense
A
Same as mRNA, can be immediately translated
22
Q
Minus sense
A
Complementary to mRNA, must be transcribed to plus strand first
23
Q
Genome shape of viruses
A
Linear or circular
24
Q
Size of virus genome
A
Usually smaller than host cells
25
Smallest known bacterial genome
110 genes, 139 kilobase pairs
26
How many genes do most viral genomes encode
A few genes to ~350
27
How many genes in a DNA virus
40+
28
What viruses have the smallest genomes
RNA viruses
29
How many nucleotides and genes do some small RNA viruses have
2000 nucleotides and 2 genes
30
Genome of unusal viruses
Use both DNA and RNA, but at different stages in the replication cycle. Not at the same time
31
Name of ssRNA viruses
Retroviruses
32
Name of dsDNA viruses
Hepadnaviruses
33
How are viruses classified
Based on the hosts they infect
34
Types of virus classifications
```
Bacterial viruses
Arachael viruses
Animal viruses
Plant viruses
Protozoan viruses
Fungal viruses
```
35
Virus specificity
Infect specific species in a kingdom and specific cell types in that species
36
Model systems
Bacteriophages
37
Extensively studied virus
Animal virus
38
Less studied virus
Plant virus
39
Size of virus
0.02 to 0.3 micrometers (20-300nm)
40
Are viruses larger or smaller than prokaryotic cells
Smaller
41
Largest virus and size
Smallpox, 200nm (same size as smallest known bacterial cell)
42
Smallest virus and size
Polio, 28nm (same size as a ribosome)
43
Capsomere
Individual protein molecules arranged in a precise highly repeating pattern around the nucleic acid making up the capsid
44
How small genome affects capsid
Some small viruses only have a simple type of protein in their capsid that repeats
45
How are capsids put together
Through self assembly or require host cell folding proteins for assistance
46
Virus symmetry
Helical
Icosahedral
Complex
47
Helical
Rod shaped viruses (TMV)
48
How is the length of the helical virus determined
Length of nucleic acid
49
How is the width of the helical virus determined
Size and packaging of capsomeres
50
Icosahedral
Spherical viruses (HPV)
51
Faces and vertices of icosahedral
20 triangular faces, 12 vertices
52
Why is icosahedral most efficient
Requires fewest capsomeres
53
Complex
Varies, has an icosahedral head and helical tail (t4)
54
Membrane of enveloped viruses
Lipoprotein (derived from host cell) and some viral surface proteins
55
What does the envelope surround
Nucleocapsid
56
What type of virus has the highest rate of mutation
RNA
57
Role of envelope proteins
Key tp attachment and infection in animal host cells
58
What enters the animal cell during infection
The entire virion
59
What types of viruses exit more easily
Enveloped
60
How do viruses acquire their envelope
Buds off the membrane of the cell
61
Enzymes inside virions
Lysozyme like enzymes
Neuraminidases
Nucleic acid polymerases
62
Where are lysozyme like enzymes found
Bacteriophages
63
Function of lysozyme like enzymes
Make hole in the peptidogylcan cell wall and allows for nucleic acid entry
64
What is the function of the similar enzymes to lysozyme
Lyses bacterial cell to release new virions
65
Type of neuraminidase
H1N1 (h is hemoglobin, n is neuraminiidase), influenza
66
Where are neurominidases found
In animal cell viruses
67
Function of neurominidases
Destroy glycoproteins and glycolipids of animal cell connective tissue, allows virus to release from cell
68
Types of nucleic acid polymerases
RNA replicase
| Reverse transcriptase
69
RNA replicase
Assist in the replication of the viral genome and production of viral mRNA
70
Reverse transcriptase
Catalyze the transcription of RNA into DNA
71
Major difference between prokaryotic and eukaryotic viruses
Nucleic acid entry in prokaryotes
| Viron entry in eukaryotes
72
Phases of viral replication of a bacteriophage
1. Attachment of the virion
2. Penetration of the virion nucleic acid
3. Synthesis of viral nucleic acid and protein by host cell metabolism as redirected by virus
4. Assembly of capsids and packaging of viral genomes into new virions
5. Release of mature virions from host cell
73
Latent period
Newly assembled virions are not yet present outside the cell
74
Burst size
Number of virions released per cell (varies from few to thousands)
75
One step growth curve of viral replication
Increase occurs when cells burst
76
Eclipse
Genome replicates and proteins translated
77
Maturation
Packaging of nucleic acids in capsids
78
Latent period
Ecplise and maturation
79
Release
Cell lysis, budding or excretion
80
What is needed to cultivate viruses
Host cells
81
Cultivation of bacterial viruses
Pure cultures inoculated in a liquid medium or spread as lawns on an agar plate and then inoculated with virus
82
What viruses can be cultivated in tissue cultures
Animal and plant
83
Why is cultivating animal viruses more complex than bacterial
Needs to be done in tissues, requires wide assortment of nutrients such as blood serum
84
The plaque assay
Detecting and counting viruses, used to assess titer
85
Titer
The number of virions per volume of fluid, number of plaque forming units per mL
86
Plaques
Clear zones that develop on lawns of host cells where successful viral infection occurs
87
How to calculate the titer of virus sample
Counting plaques
88
What is used in quantitative virology
Plating efficiency
89
The number of plaque forming units is always ______ than direct counts by electron microscopy
Lower
90
Why might a virus fail to infect
- Assembled incompletely during maturation
| - Defective genomes or spontaneous mutation that prevents it from attaching or properly replicating
91
Major factor in host specificity
Attachment
92
What does the virion have on its surface that attach to receptors on the host cell
Proteins
93
True or false, Viruses can attach to any cell
False, receptors on the cell are specific
94
Types of host cell receptors
Proteins, carbohydrates, glycoproteins, lipids, lipoproteins, or other cell structures
95
What do receptors do for the cell
Carry out normal functions for the cell (uptake proteins, cell to cell interaction, flagella, pili)
96
What do bacteriophages release into the cell and what do they leave behind
Inject viral genome and leave behind capsid outside the cell
97
What do virions use to attach to cells
Tail fibers
98
What do tail fibers interact with
Polysaccharides on E coli LPS layer
99
How do the tail pins reach the cell wall
Tail fibers retract
100
What forms a small hole in the peptidoglycan layer to allow for entry of the viral genome
T4 lysozyme
101
What contracts for the viral DNA to pass into the cytoplasm
Tail sheath
102
What happens to the T4 capsid
Stays outside the cell
103
True or false, penetration guarantees infection
False
104
Mechanisms of prokaryotes to diminish viral infections
1. Restriction endonucleases
2. Antiviral CRSPR
3. Toxin antitoxin modules
105
Restriction endonucleases
Enzymes that cleave foreign DNA at specific sites
106
What isnt affected by restriction endonucleases and why
ssDNA and RNA, specific for dsDNA
107
How does restriction endonuclease prevent cleavage of its own DNA by restriction enzymes
Requires modification of hosts own DNA (methylation of nucleotides at sites where restriction enzymes cut)
108
Defense against restriction enzymes
Base substitution and modification
109
Base substitution and modification in T4
Cytosine replaced by 5-hydroxymethylcytosine and then glucosylated
110
Toxin for TA module
Hip A
111
Hip A
Inhibits transcription, cell growth, and viral biosynthesis (cell goes into dormancy and prevents virus)
112
What does CRSPR stand for
Clustered Regularly Interspaced Short Palindromic Repeats
113
Components of CRSPR
1. Spacers
| 2. CAS proteins
114
Spacers
Regions within chromosome that contain short repeats of constant DNA sequences alternating with short variable DNA sequences
115
What do spacers correspond to
Pieces of viral DNA or other foreign DNA
116
Nickname for spacers
Memory bank
117
What does CAS proteins stand for
CRSPR associated proteins
118
Role of CAS proteins
- Possess endonuclease activity and cleave foreign DNA
| - Create new spacers by inserting short piece of DNA into CRSPR region of the bacterial genome
119
Immunization
Genetic memory conferred when new spacers are inserted into CRSPR region of DNA by CAS proteins
120
What is considered the prokaryotic immune system
CRSPR
121
How does CRSPR maintain stability and integrity of the bacterial genome
Destroying certain plasmids and genes obtained from horizontal gene transfer
122
What is CRSPR found in
Bacteria (70%) and archea (90%)
123
How does the bacteria survive the initial viral invasion
Not well understood, may use restriction endonucleases to cleave viral DNA before infection begins
124
What environmental factors could inactivate a virus
UV light
125
What do small DNA viruses use for genome replication
DNA polymerase from the cell
126
What do complex DNA viruses use for genome replication
Encode their own polymerases
127
What does T4 encode in addition to its own polymerases
Primases and helicases and 8 proteinn DNA replisome complex
128
Replisome
Protein complex that carries out DNA replication
129
How long after enterance does it take viral transcription and translation to begin
1 minute (immediately)
130
What happens when the virus begins transcription and translation
Synthesis of host DNA and RNA ceases
131
How long does virion synthesis take overall
30 minutes
132
What is the result of virion synthesis
New virions released from lysed cell
133
Major sets of proteins encoded by T4 genome
Early, middle and late proteins
134
Early proteins
- Enzymes needed for DNA replication and transcription
- Enzymes needed for synthesis and glucosylation of T4 base hydromethylcytosine
- Enzymes that function in T4 replisome
- Proteins that modify host RNA polymerase
135
Does T4 encode its own RNA polymerase?
No, T4 specific proteins modify host RNA polymerase so it only recognizes phage promotors
136
What prevents the RNA polymerase from recognizing host promotors
Anti-sigma factor binds to host RNA sigma factor
137
What do actions by early protein result in
Switch from host transcription to phage transcription
138
Middle and late proteins
- Additional RNA polymerase modifying proteins
- Viral head and tail proteins
- Enzymes for releasing new virions from the cell
139
How is the T4 genome packaged
Genome is pumped into the head under pressure using ATP
140
What happens after the head is filled with DNA
T4 tail, tail fibers and other components are self assembled
141
How is the virion released
Late enzymes break the membrane and peptidogylcan. Lysis occurs and virion is released
142
Virulent
Viruses always lyse and kill host after infection
143
Temperate
Viruses replicate their genomes in tandem with host genome and without killing host, establishing long term stable relationship
144
Lysogeny
Most viral genes are not transcribed, viral genome is replicated with host chromosomes and passed to daughter cells
145
Lysogen
Host that harbors temperate virus
146
Lysogenic conversion
Bacteria whose pathogenic ability is at least impart linked to lysogenic bacteriophage
147
Example of lysogenic conversion
Strep. Some strains have prophages (viruses) that carry genes from toxins resulting in scarlet fever
148
How does genome exist in lysogeny
Either integrated into bacterial chromosome or exists as plasmid
149
Prophage
Viral DNA
150
How is lysogeny maintained
Phage-encoded repressor protein
151
What happens when repressors are inactivated
Lytic stage
152
What induces the lytic pathway
Cell stress (ex: DNA damage)
153
How are all viruses classified
By genomes (RNA or DNA)
154
What are most human viral diseases caused by
RNA viruses
155
Examples of RNA viruses
Polio, rabies, influenza, measles, ebola, SARS, HIV
156
What is the site of replication for animal viruses in eukaryotic cells
Nucleus
157
What do viruses bind to in animal cells
Host cell receptors, typically used for cell-cell contact or immune function
158
Why can viruses only infect certain tissues
Different tissues and organs express different cell surface proteins
159
How does entry of the virion occur in animal cells
Fusion with cytoplasmic membrane or endocytosis
160
Uncoating
Release of viral genome from capsid
161
Where does uncoating occur in animal cell
Cytoplasmic membrane or cytoplasm
162
Where do viral DNA genomes go in the animal cell
Nucleus
163
What is viral RNA converted to in the nucelus and what converts it
DNA
| Converted by enzymes within nucleocapsid
164
Virulent infection
Lysis of the host cell, most common
165
Latent infection
Viral DNA exists in host genome and virions are not produced. Host cell is unharmed unless/until virulence is triggered
166
Persistant infections
Release of virions from host cell by budding does not result in cell lysis. Infected cell remains alive and continues to produce virus
167
Transformation
Conversion of normal cell into a tumor cell
168
What does retro mean
Backwards. Flow of info from RNA to DNA instead of the other way around
169
Retroviruses
RNA viruses that replicate through a DNA intermediate
170
What do retroviruses contain
Reverse transcriptase (copies info from RNA to DNA)
Integrase
Protease
171
Do retroviruses have an envelope
Yes
172
Structure of retrovirus genome
Two identical ss+ RNA molecules
173
Genes of retrovirus
gag
pol
env
174
gag
Encode structural proteins
175
pol
Encode reverse transcriptase and integrase
176
env
Encode envelope proteins
177
What happens when retrovirus enters the cell
Envelope removed at the membrane
178
Where does reverse transcription begin for retrovirus
Nucleocapsid (only one RNA genome) --> produces single DNA strand
179
What is the single strand used for
To make a complementary strand (dsDNA produced)
180
Function of dsDNA produced by retrovirus
Enter the nucleus with integrase and incorporate retroviral DNA into the host genome to form a provirus
181
How long does the provirus last
Indefinitely
182
What happens after the retroviral DNA is incorporated into the host
- Transcription of retroviral DNA
- Assembly and packaging of genomic RNA
- Budding of enveloped virions and release from cell
183
Genome
Entire complement of genetic information
184
What is included in the genome
Genes, regulatory sequences and noncoding DNA
185
Genomics
Discipline of mapping, sequencing, analyzing, and comparing genomes
186
First genomes sequenced
Small viruses
187
When was the first bacterial genome published
1995
188
First bacterium sequenced
Homophilus Influenzae
189
How many genomes have been sequenced today
50,000+
190
True or false, the human genome has been sequenced
True
191
First eukaryotic genome to be sequenced and year
Saccgaromycos cerevisiae (bakers year) 1996
192
What can genomics tell us
1. Discovery of new genes
2. Detecting horizontal gene transfers
3. Monitoring disease outbreaks
4. Discovering CRSPRS
5. Understanding metabolism/growth requirements
6. Solving medical mysteries
7. Identifying new microbial phylas
193
Sequencing
Determining the precise order of nucleotides in DNA or RNA molecule
194
Genome annotation
Converting raw sequence data into a list of genes present in the genome
195
How do bacterial and archael genomes differ from eukaryotic
They are a series of open reading frames (few introns)
196
Open reading frames
Genes that code for funtional proteins
197
Functional open reading frame
Actually encodes a protein can be identified by a computer
198
What separates ORF
Short regulatory regions and transcriptional terminators
199
Finding and identifyinf ORF
1. Locate start and stop codons
2. Locate shine delgarm
3. Look for similarity to ORFs in other genomes
4. Codon bias
5. Look for codon consistency within the species
200
Shine delgarm
Ribosome binding sequences, generally located around 8 bases upstream of the start codon AUG
201
Purpose of locating shine delgarm
Determines if ORF is functional and which start codon is actually used
202
Codon bias
In a given species, some codons are used more frequently than others
203
What does it mean if the codon bias differs greatly from other ORFs in the species
ORF may be nonfunctional or may be functional but obtained through HGT
204
What percent of genes in a genome are clearly identified
70% or less
205
Hypothetical proteins
Uncharacterized ORFs, proteins that likely exist but whos function is currently unknown
- lack sufficient amino acid sequence homology with known proteins for identification
- may be assigned to family or general function (ex: transport protein)
206
Noncoding RNA
RNA not translated
207
Why is some RNA not translated
Lack start codons and have multiple stop codons
208
Examples of noncoding RNA
- tRNA
- rRNA
- noncoding RNA regulatory molecules
209
What organisms have the smallest genomes
Parasitic or endosymbiotic prokaryotes
210
Small genome size
112-140 kbp
211
What does small genome size mean for nutrition
Totally dependent on host, but provide host with amio acids and other nutrients the host cannot synthesize
212
Organisms with the smallest genomes
Mycoplasma (bacteria) and Nanoarchaeum (archaea)
213
Pathogen with large genome
Mycobacterium tuberculosis (4.4 Mbp)
214
Number of genes for a viable cell
250-300 genes
215
How large can bacterial genomes get
As large as some eukaryuotic microbes
216
True or false, some bacteria have more genes than eukaryotes do despite having less DNA
True, eukaryotes tend to have significant amounts of noncoding DNA
217
Largest prokaryotic genome to date
Sorangium cellulosum (14.8 Mbp)
218
In general, as genome size increases, gene content _______
Increases
219
Smaller genomes encode more _____
Transcriptional processes
220
Larger genomes encode more _____
Transcriptional regulation and signal transduction
221
What can we learn from sequencing a genome
1. Evolutionary relationships
| 2. Details about metabolic capabilities
222
Metabolic capabilities
Respiratory pathways, transport systems, chemotaxis ability
223
What genes are most abundant in cells with large genomes
Metabolism
224
As genome size decreases, the percent of metabolic genes _____
Decreases
225
As genome size decreases, the percent of genes for protein synthesis _____
Increases
226
What genes make up most of archael genomes
Energy and coenzyme production
227
What doesnt the archae have a lot of genes for
Carbohydrate metabolsim and membrane functions (transport)
228
How can genetic information be transferred
Vertically or horizontally
229
Vertical gene transfer
Informatio is passed from one generation to the next by binary fission
230
Horizontal gene transfer
Microbe acquires genes from another microbe of the same generation (genetic matetrial transfered to non offspring)
231
Types of horizontal gene transfer
Transformation, transduction, conjugation
232
True or false, Horizontal gene transfer can occur between species
True
233
What do horizontally transferred genes typically encode
Metabolic functions and virulence genes as opposed to core metabolic prosesses
"bonus DNA"
234
Bacterial transformation
Donor is dead. DNA is released and received by competant recipient cell
235
Bacterial transduction
Phage infected donor cell releases phage. Phage infects another cell
236
Bacterial conjugation
Donor cell makes copy of plasmid and sends it through tube to another cell
237
Most common horizontal gene transfer
Conjugation
238
What are horizontally transferred genes readily detectable in
Distantly related species
239
Detecting horizontal gene transfer in the genome
1. Identification of genes that encode proteins typically found in distantly related species
2. Codon bias
240
Codon bias in HGT
Stretch of DNA whos sequence differs significantly from the rest of the genome may signal horizontally transferred genes
241
Mobilome
Sum of all mobile (moveable) genetic elements in the genome
242
What does the mobilome consist of
Plasmids, prophages, integrons, insertion sequences and transposons
243
What is the basis for genetic variety
Mobilome
244
Plasmids
Small, ds, helical molecules of non chormosomal DNA (bonus DNA). Can replicate on their own and integrate into the bacterial chromosome
245
How are plasmids transferred
Conjugation
246
R-plasmid
Carries genes for antibiotic resistance
247
F-plasmid
Carries genes for conjugation tube
248
What do some plasmids encode
Toxin production
249
What is necessary for conjugation
F plasmid
250
Prophages
Integrated virus genomes that pick up a specific region of the host genome (specialized transduction) when the prophage initiates another cycle of infection
251
Specialized transduction
Phage DNA inserts itself into the bacterial host at a particular site
252
What does the imprecise exision of phage DNA contain
Both phage and speicifc genes from host DNA, genes for phage replication are missing
253
What genes are transduced
Genes adjacent to the insertion site
254
Transposition
The ability of a genetic sequence to move from one location to another
255
Transposable element
Mobile genetic sequence
256
Insertion sequences
Simplest type of transposable element
257
What are insertion sequences composed of
Short DNA segments (~1000 nucleotides long)
258
What is specific to each insertion sequence
Terminal repeats (10-50 base pairs in length)
259
What is the only protein encoded in insertion sequences
Transposase
260
Transposase
Enzyme needed for transposition
261
Where are insertion sequences found
Chromosomes and plasmids
262
Mechanism of insertion sequences
"Copy and paste"
| Copy randomly inserts itself into the bacterial chromosome or plasmid. Original IS remains in place
263
Effect of insertion of insertion sequences
When IS appear in the middle of genes they interrupt the coding sequence and inactivate the expression of that gene
Cause spontaneous mutations and accelerate genomic rearrangement
264
Genes encoded by transposon
Transposase and genes for toxin production or antibiotic resistance
265
Where do transposons move R genes
From one plasmid to another or to the bacterial chromosome
266
What is at the ends of transposons
Terminal repeats
267
Transposon size
Larger than IS due to the presence of additional genes
268
Where do transposons insert themselves
Most insert between genes, but can interrupt gene function sometimes if it inserts in the middle of a gene
269
Integrons
Carry multiple gene clusters called gene cassettes that move as a unit from one piece of DNA to another
270
What enzyme do integrons use
Integrase
271
Core genome
Genetic elements that are shared by all strains of a given species, genes typical of the species
272
Pan genome
Includes core plus genes present in some strains but not all strains of the species, generally very large in size
273
What do pan genomes result from
HGT of mobile elements
274
What does the pan genome cause
Major differences in the total amount of DNA and capabilities of the strain (2 strains of the same species may show significant difference in genome size)
275
Chromosomal islands (genomic islands)
Large clusters of genes for specialized functions not essential for survival
276
Where are chromosomal islands found
Main chromosome (not plasmid)
277
What is the origin of chromosomal islands
"foreign" --> transposition
278
Evidence that chromosomal islands come from transposition
1. Flanked by inverted repeats (implys whole region was inserted into chromosome by transposition)
2. Base composition and chromosomal bias differ significantly from rest of the genome
3. Found in some strains but not others
279
What makes chromosomal islands unable to move
Accumulation of mutations
280
Pathogenicity islands
Type of chromosomal island (cluster of genes) that encode virulence factors)
281
Virulence factors
Special proteins, toxins, enzymes that facilitate disease symptoms
282
What is the difference between harmless strains and virulent strains of the same species
Virulence factors
283
How much more DNA does the pathogenic strain of E coli have
11% more
284
What do the pathogenic islands of ecoli contain
Genes for attachment to host tissue and capsule to invade host immune system
285
What type of RNA viruses are immediately translated
RNA on + side
286
Virome
Entire population of viruses present in and on human body. Unique to an individual
287
True or false, healthy people are teeming with viruses
True
288
What is the human virome dominated bt
DNA viruses
289
What does the human virome also include
Plant viruses
290
What do plant viruses cause in humans
Inflammation
291
Human endogenous retrovirus (HERV)
Remnants of retroviral genes that integrate into the human genome
292
What diseases can HERVS be connected to
Autoimmune disorders
293
Most abundant viruses in the human virome
Bacteriophages
294
Where are bacteriophages concentrated in humans
Large intestine
295
How do bacteriophages benefit bacteria in humans
Transferring antibiotic resistance or metabolic genes through transduction and lysogeny - stabilizes gut microbiota
296
How do phages act as a first line of defense in humans
Phages are anchored to sugar residues produced by mucosal cells. They attack invading pathogens and kill them before they can cross the mucosal barrier
297
Phages acting as a first line of defense for humans is an example of ____
Symbiosis
298
Harmful thing pahges do with bacteria in humans
Enhance the pathogenicity
299
What is increasing the pathogenicity of certain bacteria called
Lysogenic conversion
300
Example of lysogenic conversion
Only v. chlorae infected with the lysogenic phage are pathogenic
301
Viroids
Small infectious ssRNA particles that lack a protein capsid
302
What do viroids cause disease in
Plants
303
Prions
Small infections proteins that lack any nucleic acid
304
What do prions cause disease in and what type of disease
Neurological disease in animals
305
Shape of viriods
Circular
306
Smallest known pathogen
Viriods (246-399 bp)
307
What do plat diseases caused by viroids affect
Plant growth
308
Viroid structure
Forms hairpin shaped ds molecule with closed ends providing stability outside the cell
309
How does the viroid enter the plant
Through a wound (due to action of insects or mechanical damage)
310
How do viroids move between plant cells
Through plasmodesmata and vascular system
311
What do viroids mimic and interfere with in plants
Regulatory RNA
312
What do viroids yield during replication
siRNA
313
Affect of viroid siRNA
Silences/suppresses plant genes
314
Prnp in host cell encodes what
PrPc, found in healthy animals
315
Where is Prpc found
Functions as glycoprotein at the cell membrane of neural cells
316
Pathogenic form of Prpc
PrPsc
317
How does PrPsc differ from Prpc
Differnt conformation of amino acid sequences
318
What is the host range linked to
Protein sequence
319
What does PrPsc promote
Conversion of Prpc into pathogenic form
320
Shape of Prpc
Alpha helical
321
Shape of pathogenic form
Less alpha helix and more beta pleated sheets
322
What must the pathogenic protein do to cause disease symptoms
Attach to cell membrane
323
What does accumlation of Prpsc form
Insoluble amyloids leading to disease symptoms
324
What do amyloids to
Destroy brain and other nervous tissue
325
Evidence of neural damage and loss
Spongy nature of tissues
326
Amyloid diseases
Alzheimers, Huntingtons, Parkinsons, Type 2 diabetes
327
Nonpathogenic prions in fungi
Help adapt to environmental condtions
328
MAVS
Mitochondrial antiviral signaling molecules
| Accumulation triggers interferon production. Cells die but interrupt viral replication cycle so virus isnt spread
