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59 Cards in this Set

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1892, TMV, porcelain filter
1898, TMV = 'virus'
Loeffler and Frosch
1898, foot-and-mouth = virus in animals
1915, bacteriophage but didn't know was virus
coined term 'bacteriophage' as virus
1933, purified 1st virus, virus = 1/2 protein, 1/2 nucleic acid
1935, purified TMV, electron microscopy 1st applied to viruses
Bawden and Pirie
1937, showed TMV was RNA virus
Markham and Smith
1949, turnip yellow mosaic virus
found 2 particles (1= nucleic acid (key to infection) and 1 = not)
Hershey and Chase
1952, DNA (not protein) carry genetic info
Fraenkel-Conrat and Singer
1957, virus infections mirrored RNA (not protein), nucleic acid = genetic info and could cause infection alone
Brenner, Jacob, and Meselson
1959, viruses use host cell ribosomes to produce protein, virus hijack cell
possible origin of viruses - nucleic acid from protocell that lost all functions
possible origin of viruses - after acciental transfer, nucleic acid in foreign cell survive, replicate, and escape
Primordial soup
possible origin of virus - never associated with cells
Organisms culture (advantages/disadvantages)
Embryonic (in egg) Disadvantage: mutate when harvesting

Advantage: best models natural infection, sometimes only feasible culture system
Disadvantage: bioethical considerations, cost, individual variations
Organ culture (advantages/disadvatages)
Advanage: one organism can yeild multiple organ models, similar to natural infection
Disadvantage: many cell types present, no homeostasis, technical difficulties in sustainability (not natural environment)
Cell culture (advantages/Disadvantages)
Advantages: control environment, little intercell variation, lab convenience (grow quick)
Disadvantage: mutate so don't resemble original, least like natural environment
Uses of Cell culture
study cytopathic effects (effects of virus on cell type); study viral biology (replication); test response to agents; test virility; viral plaque assay (infection)
use of antibodies to bind viruses
Application: ID, infectivity, quantification
HA/HIA/ELISA/Flourescence microscopy
Hemagluttination Assay
plate out equal number of RBC to each well, add virus - if enough virus then RBC will stick together
Virus ok until too much antibody added
Hemagluttination-Inhibition Assay
add virus antibody to all wells, add virus, wait, add RBC
Antibody protected until too much virus
ELISA (enzyme-linked immunosorbent assay)
Add antibody, add antigen (bind to antibody if for that disease)(cause sandwich ELISA), enzyme added and bind, add marker
Genetic Technology
PCR, sequencing method (determine gene code), computer programs (compare sequence)
Microscopy without light
Use electrons (shorter wavelength), high resolution, use dead specimens, no color
Transmission electron microscopy
best for of EM for biology, thinly cut specimen coated in metal, electrons pass through thinner areas readily
Scanning EM
most detail, electrons bounce of specimen not transmitted through
rod-shaped spiral, ex. TMV, usually plants, single capsomer type
Why helix? virus use non-symetrical shapes to house genetic materials, helix maximizes bonding with nucleic acid, max stability
sphere made of flat tiles, general bauplan for symmetry
Why? smaller gene/subunits better (economy)
Why icosahedral over dodecahedral?
less number of faces with less tight corners (tighter packing at joints = increased energy don't want)
ex. influenza, helical(variety) or icosahedral(animals) inside, from host cell, layer of viral proteins between capsid and envelope (glycoproteins)
Comples viruses - head-tail
ex. bacteriophages, bacteria only, head = icosahedral and tail = helical
Complex viruses - Poxviruses
HUGE oval with studs, more nucleic acid, more complex, more genes, lots of layers
Preferred Capsid arrangement of human pathogens
Icosahedral (non-enveloped) and Helical enveloped = common
Positive sense RNA
identical to mRNA, can't reproduce mRNA from it
Negative sense RNA
complementary to mRNA, can produce mRNA directly from it
Baltimore Scheme Class 1
dsDNA as template
Animals: Pox, mono, HPV
Plants: none
Baltimore Scheme Class 2
ssDNA template
(dsDNA as intermediate)
Animals: fifth disease
Plants: bean golden mosaic virus
Baltimore Scheme Class 7
partial dsDNA
RNA as intermediate (positive sense)
mRNA as template for replication (not original)
Always in circular form
Animals: Hep B
Plants: cauliflower mosaic virus
Baltimore Scheme Class 3
dsRNA with RDRP carry in
mRNA as template
Animals: rotavirus
Plants: white clover cryptic virus
Baltimore Scheme Class 4
ssRNA, positive sense
dsRNA as template
original strand must be converted to negative strand before mRNA generated
pdsRNA as intermediate
makes RDRP (not carry in)
Animals:Norwalk, west nile, yellow fever
Plants: TMV, many!
Baltimore Scheme Class 5
ssRNA, negative sense (RDRP)
mRNA generated straight from original strand
pdsRNA as intermediate
Animals: ebola, influenza, measles
Plants:tomato spotted wilt virus, potato yellow dwarf virus
Baltimore Scheme Class 6
dsDNA as intermediate and template
Animals: retrovirus, HIV
Plants: none
ORF (open reading frame)
cadence in which nucleic acid is read, gene can encode for more than one proteinm max of 6 per protein (most seen = 4)
Ex. Hep D (delta agent) need Hep B (helper)
Stapler (helper) needs staples (satellites)
satellite viruses encode their own protein, satellite nucleic acids do not have own protein ('naked')
only in plants, usually ssRNA, circular, complementary (nucleic acid can fold back on itself), no protein just nucleic acid, short
Direct repetition on end
same sequence on 5' and 3' end if read in same direction (ABC.....ABC)
Indirect repitition on end
same sequence if you read 5 to 3 and 3 to 5 (ABC.....CBA)
ex. T4 phage, tandem repeats of genome that not seperate, individual nucleic acids are cleaved randomly
point mutations
change in letter, switch one for another, changes in genetic sequence, more common in RNA
recombination mutations
'viral sex', swapping of genetic info, equally common, recombination in segmented RNA genomes = reassortment
Class V: Paramyxoviridae, pathogenizes only humans
Black's island data - correlations between population size and sustainability of measles, need 500,000 or measles die out (start in Mesopotamia 6000 years ago)
Class V: Orthomyxoviridae, 3 genra (A,B,C) - A = severe in humans but in mostly animals, C least sever and in humans
Antigenic drift
point mutations (change in H and N), localized epidemics, immune individuals drive drift - must mutate so survive
antigenic shift
rare and major change in H and N, reassortment, global pandemic
Ebola and Marburg
Emerging Viral Disease, Class V: Filoviridae
don't know reservior, no treatment
West Nile
emerging viral disease
Class IV: Flaviviridae
no treatment, birds/mosquitos are host
Multiple Sclerosis
Myelin-specific CD4+T cells attack oligodendrocytes (which protect myelin sheath)
Cause: HHV? - guilty-by-association