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Microbiology > Replication of Virus > Flashcards

Replication of Virus Flashcards

1
Q

what do normal cells transcribe DNA in the nucleus to?

A

positive single stranded mRNA

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2
Q

what must viruses produce in order to be recognized by cellular ribosomes

A

mRNA – so it can be translated

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3
Q

examples of dsDNA viruses

A

polyoma, papilloma, adeno, herpes, pox

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4
Q

what is the promoter for polyomavirus

A

SV40

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5
Q

what are the different classes of virus according to the genome they carry

A 
class I: dsDNA virus
class II: ssDNA virus
class III: dsRNA
class IV: + ssRNA virus
class V: -ssRNA virus
class VI: +ssRNA virus, RT
class VII: dsDNA virus, ssRNA intermediate, RT
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6
Q

how do class I: dsDNA virus make +mRNA

A

they use host CELLULAR ENZYMES to transcribe IE (immediate early) and/or Early (E) mRNA

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7
Q

what happens with the IE mRNA

A

they get transcribed to IE proteins –> transcribed to E-mRNA —> translated to E-proteins

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8
Q

what are the functions of E-proteins

A

they replicate parental DNA and late (L) mRNA –> translate to L proteins —> assemble into capsids

tend to have regulatory functions in general

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9
Q

what does the capsid do in dsDNA once it is formed

A

incorporate the viral DNA to make mature virus

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10
Q

what is the exception to the dsDNA mechanims

A

pox virus – it enters the cell with all the machinery it needs and commands membrane to come to them then poke holes to get out of the cell

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11
Q

where are the capsid proteins for dsDNA virus from?

A

L (late) genes

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12
Q

example of a class II: ssDNA virus

A

parvovirus

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13
Q

where does replication of ssDNA virus occur and what happens with the strands of DNA

A

nucleus of actively dividing cells: go from a (-) strand to a template for a (+) strand

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14
Q

mechanism to form mRNA in ssDNA virus

A

ssDNA —> dsDNA (using cellular enzymes)
dsDNA –> mRNA (using cellular enzymes)
mRNA –> viral proteins

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15
Q

what is the function of the viral protein

A

they make up capsids which surrounds viral DNA in progeny virus

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16
Q

are there immediate early and early protein produced in ssDNA viruses

A

nope

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17
Q

shape of parvovirus and are they enveloped or not

A

icosahedral and nah not enveloped

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18
Q

how are the viruses released in ssDNA viruses

A

via lysis of cell

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19
Q

what is the consequence of dsRNA not being able to function as an mRNA

A

Class III viruses must package an RNA polymerase to make mRNA after infection of host cell

(genomes segmented)

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20
Q

type of polymerase is used in dsRNA viruses

A

RNA dependent RNA polymerase

RNA dependent - because that is the type of genome it is reading
RNA polymerase - because that is the type of genome it is making

21
Q

example of dsRNA virus

A

reovirus, birnavirus, rotavirus (member of reovirus)

22
Q

mechanism of dsRNA virus when forming mRNA

A

dsRNA is transcribed to viral mRNA (v-mRNA) using a RNA dependent RNA polymerase

v-mRNA gets translated to structural and non structural proteins

23
Q

what is an immature capsid in dsRNA virus and why is it formed so early

A

immature capsid are formed from the resulting viral proteins – capsid formed early because dsRNA looks foreign to the body so for protection, it needs the immature capsid

RNA replication will be concurrent with the packaging of genome segments

24
Q

what happens once mRNA is packaged into the immature capsid

A

mRNA (viral) is copied within the capsid to form more dsRNA so more mRNAs can be formed

25
Q

what does rotavirus cause in young children and infants

A

acute gastroenteritis

26
Q

where does replication of dsRNA occur

A

cytoplasm

27
Q

example of +ssRNA virus

A

Picornavirus, togavirus, coronavirus, flaviviruses

28
Q

why is a +ssRNA virus considered directly infectious

A

+ss vRNA can be infectious without viral proteins

the ends of the genome is modified 􏰁–> 5’ end - protein or methyl. nt cap and 3’ end by poly A

once modified, they look exactly like mRNA

29
Q

what are the two types of +ssRNA virus

A

IVa +ssRNA and IVb +ssRNA

30
Q

difference between the two types of +ssRNA virus

A

IVa: the infectious +ssRNA gets translated into one polyprotein which is then cleaved by proteases into multiple viral proteins

IVb: the infectious +ssRNA gets translated into several proteins

31
Q

what happens in non structural vs. structural proteins in class IV

A
  • Non-structural proteins: transcribe parental (+) RNA into (-) RNA which in turn is transcribed to (+) RNA
  • Structural proteins: make up capsids which incorporate viral RNA􏰀 into progeny virus
32
Q

where does the virus replicated in +ssRNA

A

cytoplasm

33
Q

what does picornavirus include

A

Include poliovirus, hepA, rhinovirus, and enteroviruses

34
Q

example of class V: -ssRNA

A

Orthomyxovirus, Paramyxovirus, Bunyavirus, Filoviruses, influenza, Hantavirus

35
Q

what copies the -ssRNA

A

virus specific polymerase because our cells do not have the machinery to do it

RNA dependent RNA polymerase

36
Q

what are the two types of class V -ssRNA

A

Va: non segmented
Vb: segmented

37
Q

mechanism of making mRNA in -ssRNA viruses

A

-RNA is read by virus associated premade polymerase —> +RNA –> mRNA –> viral proteins

38
Q

what happens after the assembly of the capsid in -ssRNA viruses

A

incorporation of the genomic RNA and viral proteins, including the virus RNA polymerase into the􏰁 progeny virus

39
Q

examples of +ssRNA virus, RT

A

retroviruses like HIV and HTLV-1

40
Q

mechanism of +ssRNA virus, RT

A

RNA genome use reverse transcriptase (which virus) has to make DNA copy (provirus)

provirus –> viral mRNA –> viral structural and non structural proteins

41
Q

is +ssRNA virus, RT directly infectious

A

no it is not

42
Q

difference in structural vs. non structural proteins in +ssRNA virus, RT

A
  • Non-structural proteins: may be RT and other polymerases

* Structural proteins: assemble into the capsid

43
Q

what is considered the mature virion in +ssRNA virus, RT

A

The capsid incorporates the viral genome AND the nucleoproteins, including RT into 􏰁 progeny virus

44
Q

example of class VII – ds DNA Viruses, ssRNA intermediate, RT

A

Hepadnavirus and HBV

45
Q

mechanism of class VII - ds DNA viruses, ssRNA intermediate, RT

A

partially ds DNA –> ds supercoiled DNA using virus polymerase –> goes to nucleus for transcription to v-mRNA and viral pregenomic mRNA –> various structural and nonstructural proteins

46
Q

what does the capsid do in class VII - ds DNA viruses, ssRNA intermediate, RT

A

they package the structural proteins with the pregenomic mRNA and the viral polymerase

47
Q

what occurs with the pregenomic mRNA

A

they get turned back to partially dsDNA using RT then the virus begins to mature

48
Q

HBV has a strict tissue tropism to what organ

A

liver

Microbiology (39 decks)

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