question

classification of animal Viruses, taxonomy criteria based on what 3 things

answer

genomic structure
viral particle structure
presence of absence of envelope

question

genomic structures include

answer

single or double stranded
DNA or RNA

question

Virus particle structure include

answer

isometric
helical
pleomorphic

question

Groupoing based in transmission route of the virus, what are 4 groups

answer

enteric virus
respiratory virus
sexually tranmitted virus
zoonotic virus

question

enteric virus

answer

generally transmitted via fecal-oral route
often cause gastroenteritis
some can cause system disease

question

respiratory virus

answer

usually inhaled via infected respiratoy droplet
generally remain localized in repiratory tract

question

zoonotic virus

answer

transmitted from animal to human via animal vector

question

sexually transmitted virus

answer

can cause lesions on genitalia or cause systematic infections

question

replication cycle of animal viruses is similar to virulent bacteriophage cycle

answer

true

question

what are the steps of reproduction fro animal viruses

answer

attachment
entry into suseptable cell
targetting the site of viral reproduction
uncoating of viron
syntheis of nucleic acids and proteins
assembly /maturation/release

question

absorbtion / attachment

answer

viral surface protein mediate attachment to specific host receptor, spikes attach to glycoproteins most frequently, and often require attachment to two different receptors

question

entry

answer

viruses enter the cell whole, because animal cells do not have a rigifd cell wall

question

how does the virus achieve penetration

answer

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

question

do viruses enter the cell intact?

answer

yes but the require an uncoating step to release the nucleic acid from the protein coat.

question

what are early genes jobs in the replication process of DNA virus

answer

to encode proteins envolved in the take over of the host and in synthesis of viral DNA and RNA

question

where does viral DNA replication usually occur

answer

in the nucleus of the host

question

Early mRNA synthesis is done usually by

answer

host RNA polymerase

question

what are the simplist of DNA viruses

answer

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

question

when is the viral DNA replicated in paroviruses

answer

only during the S period of the cell cycle

question

replication in Herpes Simple Virus

answer

use host RNA polymerase for synthesis of early viral mRNA Related to regulatory proeints and enzymes required for viral DNA replication

question

The herpes Simplex virus uses what fir the replication of the genome

answer

virus encoded DNA polymerase

question

INfluenza Virus replication

answer

negative strand of ssRNA virus,
use virus associated, RNA- dependant RNA polymerase to synthesis mRNA

question

Wat does the influenza virus use to form double stranded RNA to transcribe viral RNA genome

answer

viral replicase

question

compare positive strand ssRNA with negative mRNA

answer

positive strand ssRNA use the viral genome as the mRNA to form massive polypeptide which is then cleaved or processed to produce various proteins

question

HIV reproduction CYcle

answer

HIV is a retrovirus

question

what is A retrovirus

answer

it converts its RNA genome into DNA and inserts this into the genome of the host cell

question

during assembly capsid proteins are encoded by

answer

late genes

question

during assembly with naked viruses

answer

empty procapsids form
nucleic acids then insert by some unknown mechanism

question

during assembly with envelope viruses

answer

in most cases similar to assembly of naked virus, the site varies either the cytoplasm or the nucleus

question

lipid draft?

answer

microdomain in membranes with specific embedded proteins that seem to be involved in virion assembly

question

naked viruses are usually released by

answer

lysis of the host cell

question

cytocidal infection

answer

usually results in cell death

question

during cytocidal infection

answer

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

question

can envelope viruses have cytocidal effects?

answer

yes

question

envelope viruses release virions when

answer

the virus encoded proteins encorporated into the host membrane
nucleocapsid buds outward and is surrounded by a modified host membrane

question

with envelope viruses formation of envelope and release usuallt occur concurrently?

answer

trueq

question

relationships of viruses and their hosts are divided into two catagories

answer

acute- rapid onset and usually short duration
persistant- can last many years

question

acute infection

answer

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

question

persistant infection

answer

viruses are continuously persistant in the host

question

what are 3 possible causes to persistant infection

answer

integration of viral genome into host genome
decrease in antigenicity of virus
mutation to less virulent and slower reproducing form

question

persistant infections can be divided into three catagories distinguished by detection of virus during period of persistance

answer

latent infection
chronic infection
slow infection

question

Latent infections

answer

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

question

during reactivation of latent infections what happens

answer

infectious particles can be detected
symptoms of reactivation and inital disease may differ
examples herpes simplex virus ( cold sores)
shingles (zoster)

question

chronic infection

answer

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

question

best example of chronic infection

answer

hepititis B aka serum hepititas

question

best example of reactivation od a latent disease

answer

herpes ( cold sores)
shingles (zoster)

question

slow infections

answer

infectious agent gradually increase in amount over long periods of time
no significant symptoms apparent during this time

question

what two groups of infectious agents cause slow infections

answer

lentiviruses ( retroviruses0 which includs HIV And prions

question

how can viruses alter genes

answer

mutation- virus may become more virulent, virus might also become easliy transmitted

question

how else can viruses alter genes

answer

genetic reassortment - occurs in segmented viruses
these have genomes divided into different segments - each coding for different information

question

during genetic reassortment-- viruses infect the same cell

answer

2, each virus encorporated segments of viral DNA, one segment comes from one virion the rest comes from the other virion

question

what is responsible for antigenic shift and antigenic drift in influenza virus

answer

reassorment

question

does the number of plant diseases caused by viruses have a major economic importance?

answer

yes

question

how can infection be recognized by plant viruses?

answer

pigment loss
markes on leafs and fruits
tumors
stunted growth

question

plants usually recover from viral infections?

answer

NEGATIVE

question

all infections from plants are bad?

answer

no they are not

question

most plant viruses are

answer

RNA VIRUSES

question

plant viruses differ alot from animal and bacterial viruses

answer

false

question

plant virus transmission usually causes damage to plant

answer

true

question

do viruses attach to specific receptor site on plants?

answer

no

question

how do viruses infect plants

answer

through wound in plant cell wall

question

how are plant viruses traferred by

answer

wind, animals seeds, tubers, soil and pollen grafting healthy plants to infected plants

question

what are the most important agents of transmission in plant viruses

answer

insects, they act as vectors, their feeding by- passes cell wall protectiion, also leaves a wound which viruses can infect

question

many plant viruses are resistant to inactivation

answer

once started infection spreads from cell to cell through plasmodesmata

question

replcation of plant viruses is similar to bacteria and animals except

answer

capsid remains outside the cell, tobacco mosaci virus, filamentous, RNA virus

question

RNA replication is unclear if replicated by host ----- or virus encoded enzyme

answer

host RNA dependant RNA polymerase

question

protein synthesis in plant viruses

answer

processed viral genome serves as mRNA and new virions assemble spontaneously

question

Viriods

answer

define group of pathogens much smaller and distinclty different from viruses

question

viriods consist of

answer

small, circular, single- stranded RNA molecule

question

do virions have a protein coat?

answer

no, therefore resistant to proteases

question

do virions act as mRNA molecules

answer

no

question

how do viriods replicate

answer

anonomously in suseptable cells

question

RNA might be replicated in virions by

answer

rolling circle method using host RNA polymerase

question

are single virions capable of infecting a cell

answer

yes

question

viriod RNA is

answer

circular and resistant to nuclease digestion

question

all identified virions infect plants

answer

true, mechnaisms are unknown some cause latent infections

question

diseases include from virions

answer

potatoe spindle tuber
chrysanthemum stunt
cadang-candang

question

prions are

answer

protein infecting agents

question

what are linked to a number of fatal diseases

answer

prions

question

all afflictions of prions cause what

answer

brain degeneration

question

how does prions cause brain degeneration

answer

the brain tissue developed sponge like holes, disease termed transmissible spongiform encephalopathies symptoms may not appear for many years after infection

question

currently thought that PrP( prion proteins) is present in " normal" form in host animal but ------- is what is thought to cause diease

answer

to altered PrP

question

how did the altered prion arise

answer

by the gene that encodes for normal prion protein, the mutation caused protein to have different folding properties, the mutated protein resistant to preteases

question

prions are resistant to Uv light and nucleases due to

answer

lack of nucleic acid

question

how are prions inactivated

answer

by chemicals that denature proteins

question

normal prion proteins are sensative, but prions are resistant to what enzyme

answer

protease

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