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DD/BL unit 3 > Virus structure and function > Flashcards

Virus structure and function Flashcards

1
Q

Property of virus

A

submicroscopic, obligated intracellular parasite, uses host to replicate ans assemble progeny

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2
Q

Viral Classical system:

A

Nature of genetic material (DNA/RNA)
Symmetry of capsid
Naked/enveloped
Dimensions of virion/capsid

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3
Q

Baltimore system viral calssificaiton based on:

A

Central dogma (DNA, RNA, Proteins)

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4
Q

Baltimore first principle

A

Small finite number of nucleic acid copying strategies

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5
Q

Baltimore second principle

A

Viral genome in cell makes mRNA (viral genome must provide mechanisms for syn of mRNA)

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6
Q

7 classes of viral genome configuration

A 
dsDNA
gapped circular dsDNA
ssDNA
dsRNA
ss+ RNA
ss- RNA
ss+ RNA with DNA intermediate
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7
Q

3 main function of virion proteins

A

protection of genome
Delivery of genome
Mediate interaction with host

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8
Q

Two hypes of capsids

A

helical and icosahdral

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9
Q

Helical capsids arranged by:

A

identical subunits - rotational symmetry/irregularly shaped protein –> disk

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10
Q

Icosahedral capsids are:

A

form hollow quasi-spherical structure with genome inside.

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11
Q

Envelopes - define and source

A

lipid bilayers during assembly/budding - with viral glycoproteins embedded

plasma membrane, ER, golgi

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12
Q

Envelope functions

A

entry and host range determination
Assembly/egress
Evasion from immune sys

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13
Q

Describe growth curve of virus life cycle

A

One step
Eclipse phase
Latent period
plaque forming units shoots up after latent period

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14
Q

Eclipse period:

A

particles broken down, release genome

No PFU - Not infectious

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15
Q

Latent period

A

Time from initiation of infection to release infectious virus particle from cell

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16
Q

5 main things happen during latent period:

A

attachment of virus to cell
Entry of virus into cell/uncoating of viral genome
Viral gene expression
viral genome replication
assembly of new virus/egress to new particles

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17
Q

Carbohydrate receptor tend to be _____ ______ than protein receptor (and why)

A

less specific

Same config of carb side chain on many diff glycosylated membrane bound molecules

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18
Q

Entry is an energy ______ process

A

dependent (cell must be metabolically active)

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19
Q

2 ways for virus to enter cell

A

endocytosis -> nedosomes -> escape

Enveloped -> fusion with cell membrane

20
Q

Uncoating (define)

A

viral particle enter cell, capsid removed, genome exposed

21
Q

Gene expression for DNA virus

A

ds, gapped, ss = transcribe mRNA using (-) strand as template
Uses: Host RNA pol II (nucleus)
mRNA capped/poly adenylated

22
Q

Poxviruses are unqiue in their gene expression - why?

A

replicate in cytoplasm - encodes own RNA polymerase

23
Q

All RNA viruses make an viral enzyme called ____________?

A

RNA-dependent RNA polymerase (RdRp)

24
Q

RdRp function

A

production of mRNA and replication of RNA genomes

25
Q

+ vs - strand RNA virus gene expression

A

+ = translated directly by cellular ribosomes. Amp of mRNA copy number/subgenomic mRNA by RdRp

  • = transcribe + mRNA
    package RdRp in virus particle
26
Q

Retroviruses uses what enzyme?

A

reverse transcriptase - RNA to DNA - integrate into host - transcribed with host cell encoded RNA pol II

27
Q

dsDNA viral replicate (location and methods)

A
  1. nuclear - cellular factor, viral pol, accessory factors

Cytoplasm - largely independent of cell machinery

28
Q

ssDNA virus replicate (location)

A

nucleus

forms ds intermedate - template for syn ssDNA

29
Q

Gapped circular ds DNA replicate

A

Virally encoded reverse trasncriptase - mRNA to DNA viral genome
Gaps must be filled in before transcribed

30
Q

Icosahedral capsids packaging of genome by (1) or (2)

A

(1) capside assembles around genome

(2) genome fed into preformed capsids

31
Q

Egress by naked capsids viruses typically ______

A

cell lysis

32
Q

Egress by enveloped typically

A

budding
From plasma membrane - extracellular environment directly
From ER/Golgi - secreted from infected cell

33
Q

Primary initial routes of virus infection:

A

respiratory, alimentary, genitourinary

Also: mucous membrane, skin abrasion, parentally

34
Q

Successful initial infection requires?

A

Sufficient virus, host susceptible, host permissive, low host defense

35
Q

Sufficient virus

A

free virus particle must sruvive environmental exposure/abundant enough in concentration

36
Q

Tropism defined as:

A

infect certain tissues and not other - tissue specificity

37
Q

site of initial replication (local/systemic)

A

Epithelium both

38
Q

Secondary replication sites (local/system)

A

none

lymphoid organs, lungs, skin

39
Q

Incubation and immunity (local vs systemic)

A

1-3 days vs 10-21 days

Short vs lifelong

40
Q

Antibody to resist acute local/systemic?

A

Local: IgA
Systemic: IgG and IgA

41
Q

Chronic viral infection described as

A

ongoing infection/replication with mild/inapparent disease

42
Q

Persistent vs latent

A

continue to produce new virus vs No infection detected but can reactivate/recrudescence

43
Q

Slow chronic infection

A

no symptoms initially, long incubation, may induce immune response. Eventually deterioration/death

44
Q

Example of acute local, systemic, chronic, latent, slow

A 
cold/diarrhea
Smallpox/measles
Rubella
VZV
AIds, cancer
45
Q

Transforming viral infection: define

A

integrate to host -> activate/supress oncogene/TSG

Tumorigenesis

DD/BL unit 3 (16 decks)

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