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MIMM-211 final > Virology #1 > Flashcards

Virology #1 Flashcards

1
Q

Importantce of virus sturdy

A

Make up most of Eath living matter

67.7% of human=composed of virus (viral genome in our DNA)

Can be harmful disease/cancer… can enhance health

Provide toolds and models system for our discovery of fundam princple of mol. biology
Engineed virus to deliver gene therapy or deliver vaccine

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2
Q

GEneral characteristics of virus

A

Virus: genetic element that can mulstiply only in a living cell (host)
Not living, cant reproduce indepently

Obligate intracellular parasite: Need host all for energy, metabolic intermediate, P synthesis

Virus particle (virions): Extracellular form of a virus: Exist outside of the host and facilitate trans. for 1 host to other

Repl./Rep occus only infection (entry into host cell): Cause inf ina ll living things

Contain nucleic acid (DNA/RNA): No cytoplasmic memb or organelle

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3
Q

Intraceluuluar state

A

CApside removes
Virus exists as a nucleic acid

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4
Q

EXtracellular state (virions)

A

P coat capside around nucleic acid

Nucleic acidand capsid=nucleocapsid

Some have phospholipids enveloppe (phosp. bilayer form host cell memb. and viral P)

May possess glycoproteins (spikes-projections from outer surface. rEcognized and bind of host cell)

Outermost layer: protection and recognition sire for host cells

Cehck pic

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5
Q

Discovery and origin

A

Chemist Adolf Mayer: tobacco mosaic disease (TMD)=transmissible from diseased plant to healthy plan

Bacteriologist Dimitri Iwanowski: filtered sap of diseased plant thry poralain filter that was designed toretain bact

Chemist Wendell Sanley: Nobel prize for isolation, characterization and crystallization of Tobacco Mosaic Virus (TMV)

Bacteriologist Sarah Steart: Pioneered the concept that some viruses can lead to cancer

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6
Q

More hst

A

No deinitive explanation for the origin of virus exists
Viruses may have arisen either prior to or form cells

Hyp: viruses require host all:
Viruses evolved after all first appeared
Viruses were around dugin RNA world

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7
Q

Why they appeared

A

MEchanisms to quicly move genes

Viruses enriched genetic diveristy of hosts by facilitating gene transfers

Especially relevant for prokaryotic cells (horizontal gene transfer)

Possible that earliest viruses co-existed with host cells evolved killing host later

Viruses as part of the “RNA wolrd” playes a rold in R/DNA transitions

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8
Q

RNA to DNA transition

A

Some RNA viruses evolved DNA genome to protect their genome from cellular ribonucleases (cellular enzyme that destroyt foreign RNA)

DNA is more stable than RNA
Use of cellular replication machinery ro replicate

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9
Q

Virus everywhere

A

Occupy all org. and found in all type of habitat

Infect bact, fungi, animals plants, humans

Most abundant m/o on the planet

94% of nucleic acid containing virus

Small size so only 5% of biomass on this Earth

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10
Q

Climate change affect spread of disease

A

Shift geo range of 3100mammal species and virus they carry by 2070

Increasingly driving the encounter between mammal species (novel disease)

Next 50 years: More than 15000 new cases of mamal trans.

58% to infectious diseases confronted by humanity=aggravated

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11
Q

Virus=small (expections)

A

Neeed elctron microscopy: 100M poiovirus and side by side in period

Giant virus:
(nucleocytoplasmic large DNA virus-NLDV)
OWn viral parasite
Challege of evolution

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12
Q

nucleocytoplasmic large DNA virus-NLDV

A

often able to replicate in both the host cell nucleus and cytoplasm…

2003: Minivirus (mimmick microbes) in amoeba host
Large capsid with hilaments ectending
LArge DNA genome (1000 gene VS 10 usully)

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13
Q

Own viral parasite

A

Virophages: Small DNA viruses that replicate only in all co-infected with a giant virus use viral replication factory established by giant virus

Sputnik: First virophage discovered, only replicate in Mimivirus-infected amoeba cells

Virophage=parasite erslationship with coingecting giant virus (Sputnik reduces Mimivurs rep. by 7-%)
Virophage could improve survival of host by preventing ex lysis

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14
Q

Challenges of evolution

A

Infect only Euk unicellular host
Genome large and dense: Setal gene from host to be giant

Hyp: origin=bact/archea but qcuired gene by lateral transger

Giant viruses played impo role in evol of euk thry gene exhange

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15
Q

Most are not pathogenic

A

38 OTR/insdie body rn
some cause illness
Some co-existal with us
Crucial role in ecosystee:

helo control bact pop
Influene cthe evo and diveristy of host

Bacteriphage: viruses that infect and kill bact can be use to combat bact. infection

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16
Q

Virus struture

A

Capside is made of capsomere subunit protein

Envelope: combination of lipid and P (host-derived)

MAY POSSESS VIRAL GRLYCOPROTEIN (SPIKES) : RECOGNIZED ANF BIND RECEPTOR TO HOSTCELL (TO INFECT)

Most bact. and plant virus: naked (non-env)

Most animal virus : envelopped

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17
Q

Capside (functions)

A

Protection of genome: Packaging of the nucleinc acide genome
Delivery of the fenome (non-env. virus): Capside binds to host cell receptos…2 ways:

1-Direct penetration: genomes alone enter the cell

2-Endocytosis: Host cell endocytoses the entire virus uncoating of the capside and relase the genome

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18
Q

Capside morphology

A

Helical (hollow/cylindrical)
Icosahedral (many sided)
Complec (complicated structure)

19
Q

Helical capside

A

spiral/rod
Lenght=enght of nucleic acid
Width=size and packaging of capsomere
Can only package SSRNA cuz double stranded are rigid

20
Q

Icosahedral

A

Spherical and rigid
HAd closed shell with na inside
Package everything (DSRNA/DNA OR SSRNA/DNA)

Identical triangluar faces edges, vertices, 5,3,2, identical seg so we fold them

P are pentamers and/or hexamers

Most efficient arrangement of subunit (fewest caspomere required)
Most animal viruses have icosahedral capsids

21
Q

Complex capsid

A

Not helical nor icosahedral

MAinly bacteriphages
capsid is polyhedral (tail sheath is helical)

Poxviruses: overall shape=brick-shaped (no identifiable capsids but many coat around na)

22
Q

Envelopped virions

A

ACquired from host cell during viral replciation or release (budding)

Env. P or glycoP=role in host recognition

Env=Protection from immune sys (if similar… itmask it for longer time)

Env. virus=more fragile than naked (lipid bilayer of env. =sensitive to env. change …pH, T°/// Easily disrupted by phys and chem agents and can dry out easily)

23
Q

Delivery of genOME from env. virions

A

1-Attachement of virus to host cell mem (receptos)
2Endocytosus: engulf virus by host cell… memb fusion : viral and host mem fuse and realease capside into cyto
3- Uncoating of capside to releas genome

NO STRUCURE BETWEEN STRUCTURE GENOME AND WETHER IS HAS ENV OR NOT

24
Q

Virus particles (virions are metastable)

A

Stable: Must protect the gemome (created by symmetrical arrangement of many identical portein to provide genome in infected cell)

Unstable: Must come apart quickly upon infection, undergo structural changes to relase viral genome in infected cell (structure us not permanently bonded tgtr and can be taken apart and loosened upon infection)

25
Q

Proof that the viral nucleic acid genome is the genetic code…2 experiment

A

HErshey-Chase experiment with phage T2: DNA virus that infects bact.

Fraenkel-Conratsand singers’s work with TMV: RNA virus that infects tobacco leaves

26
Q

HErshey-Chase experiment

A

Proof that DNA is the genetic material of bacteriophage T2
Viruses gown in radioactive sulfur (35S) had radiolabelled proteins 9sulfur is present in protein but not dNA)

Virus gowns in radioactive phosphorus (32P) had radiolabeld DA (phsophorus is presnt in DNA but not P)

Ceck pic

27
Q

FRaenkel-Conrat

A

Proof that RNA is the genetic material of TMV
BAsed on the creation of hybrid viruses

check pic

28
Q

Overview of viral genome

A

SS OR DS DNA OR RNA (Can be + sense or- sense)

shape of viral genome: linear, circular, segmented

Coding capacity: few gene (4-100)

mRNA (ribosome ready)=always +

Complements of + are -

(-)sense viral RNA cant be directly translated

Eukaryotic DNA viruses: mostly dsDNA (diff struc tha host cell chromos… DNA repl. in nucleus (except poxvirus))

Eukaryotic RNA viruses: mostly ssRNA (cytoplasm for RNA rep. (Exceptions like retrovirus… intra-nuclear step)

29
Q

RNA viruses challenges dogma

A

DNA–> DNA (DNA-dep DNA polym)
DNA–>RNA (DNA dep RNA poym)
RNA–>P (ribosomes)

RNA–>DNA : Reverse transcriptase (RNA-dependant DNA polymerase)

RNA–>RNA: RNA-dependant RNA-polymerase

30
Q

Genome replication and exp of RNA viruses

A

RNA virus (Except retrovirus) need a RdRP to replicate

RNA virus genome encode or carry RdRP since mammalian cells do not have it

RdRP=RNA transcriptase=RNA replciase
Check pic

31
Q

Calassification of viruses based on viral attribute

A

Attribute can be used:

NAture of nucleic acid in virion, symmetry of nucleic acid invirion, symmetry of P shell (capsid)
Presnece or abscnec of phospholipid membrane (env)
host range

32
Q

ICTV classification (International Committee on Taxonomy of Viruses)

A

Order name: Virales
Family name: Viridae
GEnus name: Virus

Viral species Descriptive common names are used, suspecies are designated by number or aletter

33
Q

Baltimore’s system of virus

A

Classify animal virus

3 criteria:

1- Nucleic acid composition of viral genome
2- The way thevriral genome is rpelicated
3- WAy the virus makes mRNAs for expression of the viral P

ALL CELLS AND VIRUSES NEED RO MAKE MESSENGER RNA TO PRODUCE THEIR FUNDAMENTAL P COMPENENTS

34
Q

Baltimores 7 classes

A

Viral mRNA uses host machinery (ribosomes) to translate their viral P

  1. dsDNA viruses
  2. (+) ssDNA viruses
  3. dsRNA viruses
  4. (+) ssRNA viruses
  5. (-) ssRA viruses
  6. ssRNA-RT viruses: (+) RNA viruses that replicate thru a DNA intermediate (require reverse transcripatse)
  7. dsDNA-RT: ds DNA viruses that replicate thru RNA intermediate (require reverse transcriptase)
35
Q

Class 1: dsDNA genome viruses

A

Similar to replication of cellular DNA :
Viral P made in the cytoplasm
Viral genome replicated in the nucleus

TRanscription: viral dsDNA genome can be immediatly transcibed into mRNA upon entry using host RNA polym.

EXceptionL Poxvirus (including smallpox virus) encodes their own DNA-dRNA-polym and do not use the host machinery

Replication: use the host machinery

CHECK PIC

36
Q

Class 2: ssDNA genome viruses

A

Cells do not use ssDNA-rarely infect humans b/c of cell sensors

TRanscription: Viral mRNAs are transcribes from dsDNA using the host transcurption machinery

ReplicationL Most of viruses have circular genomes that are replicated withing the nucleus via a ds DNA intermediatte. REquire host DNA polym to generate the compl. strand

Some viral ssDNA strand folds back on itself to form ds DNA, which is replicated by cellular DNA polym.
Newly replicated strand is relased as ssDNA

***Mammalian cells do not have RNAdRp…must encode OR… RdRp produce RNA genomes and mRNA from the RNA template

37
Q

class 3 dsRNA viruses

A

All happens in the cytoplasm

RdRp is needed to make mRNA (transc) and to make copies (repl)

These viruses must carry a RdRp in the viral particle

38
Q

Class 4 (+) ssRNA geomes viruses

A

In cytoplasm

TRansc: (+) viral RNA genome can be used directly to translate to viral P by host ribosomes (dont have to carry the RdRp in particle,,,, has to encode it)

Rel: Synthesis of complementary (-) strand by viral RdRp… (-)=template for (+)
Pic

39
Q

class 5: (-) ssRNA genome viruses

A

in cytoplasm
(-)ssRNA genome cannot be used by host ribosomes cuz not (+ ) mRNA but complement

TRansc: require RdRp to make mrNA (+ssRNA)… must carry it

Repl: (+) ssRNA can be used a s a template for replication of additional copies of (-)ss RNA

PICq

40
Q

class 6: Retroviruses or ssRNA reverse trascribing (Rt) viruses

A

Use viral reverse transcriptase (RT) to turn (+) RNA to dsDNA in cyto: Must carry RT… insert ds DNA intermediate in host genome in nucleus using ciral enzem integrase (carry)= provirus

transc: integrated pociruse used as template to make mRnA by host transcription machinery

Repl: Provirus used a s atemplate to make (=)ssRnA by host machinery

41
Q

Class 7: PAraretrovirus or dNA reverse transcurbing virus

A

PArtially dsDnA

Partially/grapped DNA converted to fully dsDNA by cellular DNA repaire mechanisme or forms a covalently closed circular DNA (cccDNA0

Tans: dsDNA transcibed into mRNA in nucleus

Repl: uses ssRNA intermediate as a template for viral reverse trsncriptasetpo make more DNA copues in cytoplasm (encode for reverse transcriptase)

42
Q

Comparing and Contrasting strategies #1

A

Viral dsDNA or RNA transcribed into mRNA via enzymes:

Class 1,2,6,7 dsDNA use host cell RNA polym (diff strategies)… check pic

Class 3,4,5, use viral RdRp

Check pic

43
Q

Class 3,4,5 =RdRp

A

Upon nifection, +RNA genome of class 4 virus is used directly by ribosomes to make RdRp to initiate viral replciation

Upon infection, genome of classes 3 and 5, cant be translated directly into ribosome… RdRp must be carried in the viral particle to initiate the vrial replication

44
Q

Class 4 vs Class 6

A

HAve a postiive RNA genome but use diff enz. to epress and replicate their genome

Class 4: RdRp
Class 6: RT, integrase and host RNA polymerase 2

check pic

MIMM-211 final (7 decks)

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