microbiology - viruses, prions and viroids Flashcards

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define virus

PARTICLES, that are infectious agents and are obligate intracellular paracites because they need a host cell to replicate


viruses are ____ specific.

host cell. (very strict and eukaryotic cell viruses cannot affect prokaryoticand vice versa. only exception is rabies


what two structural components do all viruses have and describe them.

1.nucleic acid core/genome- either DNA or RNA genetic material that can be used to classify viruses
2.capsid-protein cote that surrounds nucleic acid core


what two other structural components can be found in viruses and describe them.

card image

1.envelope- membrane like structure that surrounds capsid. they sometime steal the membrane from their host cell but they do not function as such
2. spikes-made of glycoprotien and are associated with enveloped viruses. function as attachment to host cell


what is so special about pox viruses

they are the largest and pretty much self sufficient. size matters .they have multilayered capsids and make own envelope


describe the shapes found in viruses

1.icosahedral/ spherical


what is icosahedral/ spherical

polyhedron with about 20 equilateral triangular faces. shape of a capsid


what is helical

cylindrical-tube-like structure


what is an enveloped viruses shape

usually spherical however shape of capsid underneath can vary


what is a viron

fully assembed virus particle ; extracelluar form of virus


define nucleocapsid

genome and capsid


what is an enveloped virus?

a virus with an envelope


what is a naked capsid virus?

not surrounded by an envelope


bacteriophage, phage, φ

viruses that affect prokaryotic cells( means bacteria eating)


how do viral replication and cell replication differ

cell replication=1 to 2
viral replication= 1 to many


viral cultivation- live animals advantages and disadvantages

advantages-monkeys are close to human,s some viruses wont replicate unless in live animal, good for when we want to see effect on entire animal
disadvantages-very expensive, pediree (not working with genetially identical) and dont know genentic composition, with monkeys they come from other parts of the world and they can be different. also ethics is a factor


organ culture-(whole organ or part of organ) advantages and disadvantages

adv. they will be like they would be in the animal. you can control / maintain to a certain extent. dis- sacrifice animal, expensive and most organs dont cooperate


embryonated eggs- what is used and advantages and disadvantages

fertalized eggs typically chicken eggs. 1st type of test outside original viral place
adv. - cheap, different tissues in egg, viral propigation .
disadv- innoculating egg is not easy. cant’ see what is going on


tissue/ cell culture- what happens and what are the two types and explain them and their advantages and disadvantages

take cells (animal cells typically sticky) place in glass or plastic container. cells attach to bottom. then baith cells with some kind of medium
two types:
continuous cell lines
primary cell lines


what are continuous cell lines and what are their advantages and disadvantages

can be transferred indefinitely take growing cells in fresh container and medium and they will continue to grow) adv. passed indefinitely . disadvantage- tend not to be normal cells, eg. cancers. often form monolayer but these don’t


what are primary cell lines and their advantages and disadantages?

cells that come directly from host- adv. normal cells disadv- transfered indefinitely


what makes infecting plants so hard?

the barrier is plant cell wall because viruses can’t get inside by on their own and do so via storm damage insect damage, disease damage and things like that. once affect, spread quickly! shead in seeds


three ways plants are infected

-whole plant cultures
-plant cell protoplast
-plant tissue culture


how is a whole plant culture infected?

rub stem and leaves with virus and abrasive material


how is a plant cell protoplast able to be infected

plants w/o cell wall


why are plant tissue cultures advantages

adc- cheaper and replicate faster and get more. genetically engineer


what is a viral assay ?

methods used “enumerate” viruses


what are the two types of viral assays?

1.hemagglutination assay
2.plaque assay


when and where is hemagglutination assay useful and what do they do?

for animal viruses useful only w/ viruses w/ hemagglutininc causes red blood cells to clump together (you have to have something to hold them together)


what are the steps for hemagglutination assay

1.serially dilute viruses suspended in wells of microtiter plate
2.add same concentration of sheep red blood cells to each well
3.look for hemagg. ( if occured virus particle allows rbs to connect to another virus well and look like they are holding hands. if not occurred all break apart and there is a red dot at the bottom. titer=reciprocal of greatest dil. of virus that allows for hemagg. disadvantage is you cannot cannot compare titer of different viruses. used to monitor viral loads


what are plaque assays?

for bacterophage that lyce host cells.


what are the steps for plaque assay

serially dilute in suspended mix each solution to generate bacteria lawn incculate and count number of plaquest in bacteria. lawn and multiply diltion factor . disadvantage is that you can under estimate


what are the 2 major types of viral replication?

-productive response
-non productive response


what are the other types of replication

-non- integrative lysogeny
-persistent or chronic viral infections
-latent virus infection


what is productive response

when virus successfully infects host cell, begins to replicate and continue to, proglenine are produced and released from cell. length varies


what is non productive response

sucessfully inects ,begins to replicate but replication stops. host cell still infected but virus will not kill cell


what is non- integrative lysogeny

virual DNA does not integrate but stays in cytoplasm


what is persistent or chronic viral infections

slow productive response. infect host cells and begin replicating but it takes a long time (examples-1. hepatitis b. virus - not food born, blood born, and sexually transmitted. sometimes never goes away 2-mesles virus (rubeola) incubation period ~ 1 month. 2- epstein - barr virus (herpes virus) . causes mono )


what are latent virus infections

infects then goes dorment but may begin replicating again.( ex. herpes simplex virus type I and II.type 1-> cold sores/ fever blisters. type-> genital herpes infected for life . 2->varicella -> zoster virus - chicken pox and shingles)


what cycle does productive response go through? what do productive responses with bacteriophages do?

lytic cycle
. they lice cells open they kill them but not necessarily lice them


step 1 of the lytic cycle and describe?

adsorption- host range is defined.. very specific pairing of host and virus. if it does not pair correctly, virus will not affect. virons (use fibers) attach proteins specifically interact with host cell receptor. cell walls are typically receptors (pili, flagella) for animals glycoprotiens


step 2 of the lytic cycle and describe

penetration and uncoating- virus gets into cell and viral genome is released. occur simultaneously for bacteriophage(s) φ-> inject genome (usually all that enters) some φ-> genome inserted into bacteria cell wall for all phage the only thing that enters is genome. animal virus-. (endocytosis) membrane fusion event. fusion of envelope with some membrane of the cell via fusion protien and nuclieocapsid is entered. fusion proteins remain at surface and due to bumping cells fuse to each other. uncoating step varies


step 3 of the lytic cycle and describe

replication (synthesis)- varies from virus to virus . always occur during “eclipse phase” - time in viral replication when virus has been taken apart. does not always start here. for φ starts at penetration. (stepwise and sequential)
early functions: early mRNA ->early proteins (nucleiaces: shut down factory; polymerase)
late functions:late mRNA-> late proteins (caped proteins , spike proteins etc)


step 4 of the lytic cycle

assembly (stepwise and sequential) maturation genome is replicated, build capsid, genome is stuffed, other parts are added if needed some viruses have to get an envelope


step 5 of the lytic cycle

release- getting bacteria out of host cell
φ late proteins endolysin
animal vir-> varies considerably some have to just sit and wait. some acquire envelope s they leave or exocytosis.


what cycle does nonproductive response go though

lysogeny λ . everything goes a planned until replication stops λ jumps into bact chromosome


step 1 of lysogeny

absorption- λ example-e. coli virus


step 2 of lysogeny

penetration and uncoating


step 3 of lysogeny

replication begins


step 4 of lysogeny

if lysogeny occurs-> integration. λ DNA plants itself inside e. coli chromosomes. λ DNA is replicated along with bacteria chromosome indefinitely


step 5 of lysogeny

induction- lytic cycle (activity repressor) was keeping it off


step 6 of lysogeny

replication continues


step 7 of lysogeny

assembly of virus particles


step 8 of lysogeny

release of virus particles


what happens when replication begins in the lysogenic cycle

early protiens called λ repressor is made λ repressor blocks lytic cycle . when in effect w. coli , has two options- go productive ( lytic cycle ) or non-productive (lysogenic cycle) if enough repressor is made->lysogeny occurs


what determines is lysogeny or the lytic cycle occurs

if the cell is healthy or not


when does induction occur and what happens?

naturally occurs due to nutrient limitation and damaged DNA
in lab-> induction of lytic cycle w/ agents that damage DNA
as a result of DNA Damage bac. cell produces a protease. it cleaves (a different) repressor of a DNA repair system an it turns on
bact protease also cleaves λ repressor
lytic cycle is turned on


what are virulent or lytic viruses and what is an example?

only capable of entering productive response. ex. -> cold viruses (rino-virus)


what are temperate viruses?

capable of entering non-productive response


what is a lysogen

bacterial cell infected (dormantly) w/ φ; have medical significance


why is it hard to treat viruses? why cant you use antibiotics?

because of intamacy with its host cell. you cant use antibiotics because they target certain things.


what are used to treat viruses



what is amantadine used for?

revents influenza A by blocking penetration and uncoating steps


what is adenine arabinoside and what is it used for?

nucleotide mimic. herpes virus


what is acyclovir used for?

to block herpes virus DNA polymerase since they have it and humans don't and used for shingles


what is Azidothymidine (AZT) and why does it work?

used for HIV . works because HIV is a retrovirus


what is a retrovirus? and what makes it occur

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due to reverse transcriptase which AZT targets


what is interferon (cytosine)

chemicals produced by cells


where and when is interferion produced

produced by mammals . it is an immunoregulatory molecule
produced in response to double stranded RNA (some viruses have it), endotoxins (LPS) ,some viruses and other antigenic stimuli (something that can turn on a viral response)
function against viruses: cells virually infected prod. interferon whic triggers other cells to produce antiviral molecule * esp RNA viruses because they replicate in cytoplasm


why is interferon produced

in response to double stranded RNA which is found in some virues, endotoxins (LPS), some viruses and other antigenic stimuli


what is the relationship between interferon and viruses?

interferon functions against viruses . the cells virually infect produce interferon which triggers other cells to produce antiviral molecule *especially RNA viruses becaue they replicate in cytoplasm


Is interferon host specific? are they virus specific?

they are host specific but not virus specific


what does cancer mean

uncontrolled cell growth; cell cycle is no longer properly regulated


what is a tumor

a lump or mass of cells growing out of control


what is a benign tumor?

a noncancerous , non-spreading tumor


what is a malignant tumor

a cancerous tumor and cells are spreading (metastasis)


what are three cause of cancers?

-mutagenic agent
-carinogenic agents


what is a mutagenic agent?

induce mutations above spontaneous mutations and lead to cancerous conditions


what is a carsinogenic agent?

potential to cause cancerous conditions


what type of viruses usually cause cancer?

DNA viruses and long term viruses


what is a transforming agent virus?

tell cells to divide and induce S phase and is very dangerous


how is papillomavirus (HPV) transmitted and what are they

sexually and they are benign warts which lead to cervial cancer


what is the herpes virus I?

fever blisters that lead to lip or mouth cancer


what is the herpes virus II?

genital herpes that lead to cervical and penile cancer


what is kinds of viruses do EBV lead to?

mono which leads to hodgkins disease and burkett's lymphoma


what is burkett's lymphoma and where is it found

which is usually found in tropical parts of the world . it is usually a tumor in the jaw but is very treatable


what is the human herpes virus and when does it usually infect

a feaver and a rash that is very prevalent and usually infects in childhood


what is kaposis sarcoma

cancer of vascular epithelial tissue


what is the risk of hepadna viruses

risk of liver cancer


what are RNA viruses

some retroviruses and HTLV i and HTLV II ( human tull lymphotropnic virus and some are associated with leukemia


what is a viroid

piece of circular RNA


what is the host of Viroids

plant patogen.


what is the smallest known infectious agent

plant cell nucleus


what is the mode of infection for viroids

it blocks mRNA splicing


what is the definition if a prion

pieces of proteins ( a proteinaceous infectious particles


what are the host for prions



what is the mode of infections for prions

(coded for by host) they are misfolded protien and presence of one can cause others to misfold (we think) and causes tangles and kills them (most are not mutants


what is a example of a disease that is caused by prions

krutz-jacob disease (KJD)