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viruses part 2
viruses part 2
86
Microbiology
Undergraduate 3
07/26/2012

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Term
classification of animal Viruses, taxonomy criteria based on what 3 things
Definition
genomic structure
viral particle structure
presence of absence of envelope
Term
genomic structures include
Definition
single or double stranded
DNA or RNA
Term
Virus particle structure include
Definition
isometric
helical
pleomorphic
Term
Groupoing based in transmission route of the virus, what are 4 groups
Definition
enteric virus
respiratory virus
sexually tranmitted virus
zoonotic virus
Term
enteric virus
Definition
generally transmitted via fecal-oral route
often cause gastroenteritis
some can cause system disease
Term
respiratory virus
Definition
usually inhaled via infected respiratoy droplet
generally remain localized in repiratory tract
Term
zoonotic virus
Definition
transmitted from animal to human via animal vector
Term
sexually transmitted virus
Definition
can cause lesions on genitalia or cause systematic infections
Term
replication cycle of animal viruses is similar to virulent bacteriophage cycle
Definition
true
Term
what are the steps of reproduction fro animal viruses
Definition
attachment
entry into suseptable cell
targetting the site of viral reproduction
uncoating of viron
syntheis of nucleic acids and proteins
assembly /maturation/release
Term
absorbtion / attachment
Definition
viral surface protein mediate attachment to specific host receptor, spikes attach to glycoproteins most frequently, and often require attachment to two different receptors
Term
entry
Definition
viruses enter the cell whole, because animal cells do not have a rigifd cell wall
Term
how does the virus achieve penetration
Definition
phagocytosis in which the virus is engulfed by the cell, membrane fusion occurs with the enveloped virus when the viral envelope fuses with the plasma membrane of the host cell
Term
do viruses enter the cell intact?
Definition
yes but the require an uncoating step to release the nucleic acid from the protein coat.
Term
what are early genes jobs in the replication process of DNA virus
Definition
to encode proteins envolved in the take over of the host and in synthesis of viral DNA and RNA
Term
where does viral DNA replication usually occur
Definition
in the nucleus of the host
Term
Early mRNA synthesis is done usually by
Definition
host RNA polymerase
Term
what are the simplist of DNA viruses
Definition
paroviruses which have one small single stranded DNA (ssDNA) molecule, they have a small genome with overlapping genes that only encode capsid proteins, they use host cell for all biosynthetic processes
Term
when is the viral DNA replicated in paroviruses
Definition
only during the S period of the cell cycle
Term
replication in Herpes Simple Virus
Definition
use host RNA polymerase for synthesis of early viral mRNA Related to regulatory proeints and enzymes required for viral DNA replication
Term
The herpes Simplex virus uses what fir the replication of the genome
Definition
virus encoded DNA polymerase
Term
INfluenza Virus replication
Definition
negative strand of ssRNA virus,
use virus associated, RNA- dependant RNA polymerase to synthesis mRNA
Term
Wat does the influenza virus use to form double stranded RNA to transcribe viral RNA genome
Definition
viral replicase
Term
compare positive strand ssRNA with negative mRNA
Definition
positive strand ssRNA use the viral genome as the mRNA to form massive polypeptide which is then cleaved or processed to produce various proteins
Term
HIV reproduction CYcle
Definition
HIV is a retrovirus
Term
what is A retrovirus
Definition
it converts its RNA genome into DNA and inserts this into the genome of the host cell
Term
during assembly capsid proteins are encoded by
Definition
late genes
Term
during assembly with naked viruses
Definition
empty procapsids form
nucleic acids then insert by some unknown mechanism
Term
during assembly with envelope viruses
Definition
in most cases similar to assembly of naked virus, the site varies either the cytoplasm or the nucleus
Term
lipid draft?
Definition
microdomain in membranes with specific embedded proteins that seem to be involved in virion assembly
Term
naked viruses are usually released by
Definition
lysis of the host cell
Term
cytocidal infection
Definition
usually results in cell death
Term
during cytocidal infection
Definition
virus inhibits cellualar DNA, RNA, and protein synthesis, lysosomes are damaged, releasing hydrolytic enzymes, plasma membrane is disrupted or weakened
chromosomal disruption
toxicity from high concentrations viral proteins
Term
can envelope viruses have cytocidal effects?
Definition
yes
Term
envelope viruses release virions when
Definition
the virus encoded proteins encorporated into the host membrane
nucleocapsid buds outward and is surrounded by a modified host membrane
Term
with envelope viruses formation of envelope and release usuallt occur concurrently?
Definition
trueq
Term
relationships of viruses and their hosts are divided into two catagories
Definition
acute- rapid onset and usually short duration
persistant- can last many years
Term
acute infection
Definition
usually short in duartion
host may develope long lasting immunity
results in productive infection
produce large number of viruses during replication
disease systems result in tissue damage and infection of new cells
Term
persistant infection
Definition
viruses are continuously persistant in the host
Term
what are 3 possible causes to persistant infection
Definition
integration of viral genome into host genome
decrease in antigenicity of virus
mutation to less virulent and slower reproducing form
Term
persistant infections can be divided into three catagories distinguished by detection of virus during period of persistance
Definition
latent infection
chronic infection
slow infection
Term
Latent infections
Definition
infection is followed by symptonless period, virus stops reproducing and remains dormant for some time. During this perios symptoms, antivirus-antibodies, and viruses are not detectable
Term
during reactivation of latent infections what happens
Definition
infectious particles can be detected
symptoms of reactivation and inital disease may differ
examples herpes simplex virus ( cold sores)
shingles (zoster)
Term
chronic infection
Definition
infectious virus can be detected at all times, disease may be present or absent during extended times or may develope late clinical symptoms mild or absent for long periods
Term
best example of chronic infection
Definition
hepititis B aka serum hepititas
Term
best example of reactivation od a latent disease
Definition
herpes ( cold sores)
shingles (zoster)
Term
slow infections
Definition
infectious agent gradually increase in amount over long periods of time
no significant symptoms apparent during this time
Term
what two groups of infectious agents cause slow infections
Definition
lentiviruses ( retroviruses0 which includs HIV And prions
Term
how can viruses alter genes
Definition
mutation- virus may become more virulent, virus might also become easliy transmitted
Term
how else can viruses alter genes
Definition
genetic reassortment - occurs in segmented viruses
these have genomes divided into different segments - each coding for different information
Term
during genetic reassortment-- viruses infect the same cell
Definition
2, each virus encorporated segments of viral DNA, one segment comes from one virion the rest comes from the other virion
Term
what is responsible for antigenic shift and antigenic drift in influenza virus
Definition
reassorment
Term
does the number of plant diseases caused by viruses have a major economic importance?
Definition
yes
Term
how can infection be recognized by plant viruses?
Definition
pigment loss
markes on leafs and fruits
tumors
stunted growth
Term
plants usually recover from viral infections?
Definition
NEGATIVE
Term
all infections from plants are bad?
Definition
no they are not
Term
most plant viruses are
Definition
RNA VIRUSES
Term
plant viruses differ alot from animal and bacterial viruses
Definition
false
Term
plant virus transmission usually causes damage to plant
Definition
true
Term
do viruses attach to specific receptor site on plants?
Definition
no
Term
how do viruses infect plants
Definition
through wound in plant cell wall
Term
how are plant viruses traferred by
Definition
wind, animals seeds, tubers, soil and pollen grafting healthy plants to infected plants
Term
what are the most important agents of transmission in plant viruses
Definition
insects, they act as vectors, their feeding by- passes cell wall protectiion, also leaves a wound which viruses can infect
Term
many plant viruses are resistant to inactivation
Definition
once started infection spreads from cell to cell through plasmodesmata
Term
replcation of plant viruses is similar to bacteria and animals except
Definition
capsid remains outside the cell, tobacco mosaci virus, filamentous, RNA virus
Term
RNA replication is unclear if replicated by host ----- or virus encoded enzyme
Definition
host RNA dependant RNA polymerase
Term
protein synthesis in plant viruses
Definition
processed viral genome serves as mRNA and new virions assemble spontaneously
Term
Viriods
Definition
define group of pathogens much smaller and distinclty different from viruses
Term
viriods consist of
Definition
small, circular, single- stranded RNA molecule
Term
do virions have a protein coat?
Definition
no, therefore resistant to proteases
Term
do virions act as mRNA molecules
Definition
no
Term
how do viriods replicate
Definition
anonomously in suseptable cells
Term
RNA might be replicated in virions by
Definition
rolling circle method using host RNA polymerase
Term
are single virions capable of infecting a cell
Definition
yes
Term
viriod RNA is
Definition
circular and resistant to nuclease digestion
Term
all identified virions infect plants
Definition
true, mechnaisms are unknown some cause latent infections
Term
diseases include from virions
Definition
potatoe spindle tuber
chrysanthemum stunt
cadang-candang
Term
prions are
Definition
protein infecting agents
Term
what are linked to a number of fatal diseases
Definition
prions
Term
all afflictions of prions cause what
Definition
brain degeneration
Term
how does prions cause brain degeneration
Definition
the brain tissue developed sponge like holes, disease termed transmissible spongiform encephalopathies symptoms may not appear for many years after infection
Term
currently thought that PrP( prion proteins) is present in " normal" form in host animal but ------- is what is thought to cause diease
Definition
to altered PrP
Term
how did the altered prion arise
Definition
by the gene that encodes for normal prion protein, the mutation caused protein to have different folding properties, the mutated protein resistant to preteases
Term
prions are resistant to Uv light and nucleases due to
Definition
lack of nucleic acid
Term
how are prions inactivated
Definition
by chemicals that denature proteins
Term
normal prion proteins are sensative, but prions are resistant to what enzyme
Definition
protease
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