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HELENP CBG VIROLOGY AND IMMUNITY > CBG Lecture 20: Viral diversity > Flashcards

CBG Lecture 20: Viral diversity Flashcards

1
Q

define virus

A

a small non cellular agent consisting largely of nucleic acid within protein coat and requiring a cell for reproduction`

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2
Q

what is a way in which viruses differ from eachother

A 
genome diversity 
ss or ds
DNA or RNA
circular or linear
\+ sense or -sense
segmented or nonsegm
life cycles
replication strategy
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3
Q

name some DNA viruses

A

herpes
pox
mimi

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4
Q

name some rna viruse

A

picorna
polio
rubella
HIV

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5
Q

is herpes virus dna/rna

A

dna

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6
Q

is polio dna/rna virus

A

rna

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7
Q

is mimivirus dna or rna virus

A

dna

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8
Q

what is max size of rna virus

A

30kbp

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9
Q

what is range of dna virus

A

3-800kb

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10
Q

which viruses tend to have overlapping genes

A

those with small genomes

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11
Q

is HIV rna or dna virus

A

rna

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12
Q

what is HIV genome size

A

9kb

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13
Q

how many strands are most rna viruses

A

single stranded

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14
Q

which RNa viruses are double stranded

A

reoviruses

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15
Q

what is unusual about reoviruses

A

they are RNA double stranded

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16
Q

what ssDNA viruses are there

A

some small viruses

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17
Q

whats unusual about parvoviruses

A

v. small SINGLE stranded dna virus

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18
Q

name a circular dsDNA virus

A

SV40

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19
Q

what is unusual about SV40 virus

A

has circular dsDNA genome

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20
Q

which viruses have lower error/mutation rate

A

dna viruses, because DNAP has proofreading arm

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21
Q

what is the effect of RNA viruses having a high mutation rate

A

every RNA virus is different so get quasispecies

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22
Q

what is a quasispecies

A

virus doesnt exist as single sequence but pool of sequences making it v difficult to make vaccines

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23
Q

why is it important for big viruses to be dsDNA

A

more stable therefore lower mutation rates

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24
Q

how can RNa viruses have genome that is mostly ss but with some ds

A

because can make ds by looping structures - secondary structures eg. hairpin

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25
Q

in what direction does - sense viruses go

A

3’ 5’

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26
Q

how do -sense viruses replicate

A

produce +sense mRNA before production of viral proteins

input RNA then to +RNA then to progeny RNA then to virions which are -sense 3’5’

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27
Q

what are polarity switches

A

from virion of -sense RNa back to +sense RNA

28
Q

give example of segmented virus

A

influenza

29
Q

give example of non-segment

A

retrovirus

30
Q

give example of +sense non-segmented genome

A

retrovirus

31
Q

what genome do retroviruses have

A

+sense non-segmented genome

32
Q

how do nonsegmented viruses evolve

A

mutation

recombination

33
Q

how do segmented viruses evolve

A

mutation
recombination
assortment

34
Q

how many segments in influenza virus

A

7/8

35
Q

when does antigenic shift occur

A

when RNA segment are exchnaged between viral strains in a secondary host
no cross protective immunity to virus expressing a novel hemaglutinin

36
Q

what microscope used to see viruses

A

EM

37
Q

what is basic structure of a virus

A

genome (nucleic acid) surrounded by capsid eg.TMV

38
Q

give example of virus which has genome surrounded by capsid

A

TMV

39
Q

what does the capsid of a virus do

A

protect nucleic acid

40
Q

how can virus capsid be assembled

A

self assembly - monomeric protein units produce spherical particles
one or more capsid prteins:icosahedral formations

41
Q

name some ds segmented RNA virus

A

reoviridae

42
Q

name some nonsegmented negative strand rna virus

A

paramyxoviridae

filoviridae

43
Q

name a segmented - rna virus

A

orthomyxoviridae

bunyaviridae

44
Q

name a virus with an envelope

A

retrovirus: hiv

45
Q

name some dna virus

A

circo/parvo/papoadeno/herpes/pox

46
Q

name some host specific viruses

A

small pox and polio are human specific

47
Q

name some human specific viruses

A

smallpox and polio

48
Q

what is mortality rate of ebola

A

90%

49
Q

for most viruses, how many viral cells do you need to get exposure to to contract it?
whyh is ebola the exception

A

normally need 1000s virus eg.polio but with ebola need 1

50
Q

define zoonotic

A

infectious diseases of vertebrates that can be naturally transmitted to humans eg.rabies

51
Q

name a zoonotic virus

A

rabies

ebola

52
Q

what is WNV

A

west nile virus

53
Q

how is WNV transmitted

A

crow to crow transmission in caged birds by infected mosquitos

54
Q

what is WNV vector

A

mosquitos

55
Q

how do mosquitos become infected with WNV

A

when they bite birds infected with WNV

56
Q

what are the dead end carriers of WNV

A

uhans - the virus is not sufficient to be transmitted back to the mosquito, thereby ending transmission cycle

57
Q

why are humans dead end csarriers of WNV

A

because the virusin them is not sufficient enough to be transmitted ack to mosquto therefore ends the transmittion cycle

58
Q

whats unusual about mimivirus

A

physically big and related to other dsDNA viruses

59
Q

how many genes do mimiviruses contain

what is its genome size

A

900

1Mbp genome size

60
Q

apart from mimivirus, what virus has next biggest genome size

A

poxvirus

61
Q

how many genes does poxvirus contain

A

900

62
Q

how can you eradicate a virs

A

need to be human specific, effective vaccine, need virus to produce symptoms, need antigenetically STABLE virus

63
Q

name some asymptomatic viruses

A

WNV in some mamals

poliovirus

64
Q

how old are RNA viruses

A

up to 3.5bn yrs old

65
Q

what are similarities between HIV types 1&2

A

replicate in the nucleus
contain 2 env proteins
contain RT
envelope fuses with cell membrane

66
Q

how does adenovirus getinto host cell

A

endoctosed

67
Q

how does influenza get into host cell

A

endocytosed then fuses with the endosome in a pH dependent manner

HELENP CBG VIROLOGY AND IMMUNITY (8 decks)

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