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Virology > Viral Genomes (Lecture 6) > Flashcards

Viral Genomes (Lecture 6) Flashcards

1
Q

3 basic principles behind the viral genome

A

genomes need to be copied to make mRNA; unity in viral diversity; genome is used as a template for new genomes for new progeny

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2
Q

How is there unity in the 7 different types of viral genomes?

A

they all want to accomplish the same goal –> make mRNA

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3
Q

Why are not all (+)ssRNA are mRNA?

A

they may not be ribosomal ready, they can be preliminary mRNA

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4
Q

What are the 5 genes viruses need to have or already have with them?

A

genes that will help replicate viral genome | assembly/packaging genes | regulation and time of replication cycle | modulation of host defenses | genes that will allow it to spread and infect other cells

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5
Q

What are 4 genes that viruses DON’T have encoded in their genome but may need?

A

protein synthesis machinery | synthesis of biomembranes | synthesis of energy | centromeres/telomeres

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6
Q

Why would viruses need telomeres?

A

to maintain genome so as it replicates, it won’t get totally wiped out

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7
Q

What are the 3 viral genes needed for infection?

A

capsid proteins | viral receptor-binding protein | polymerase (either to have it with them or something to induce activation host-cell polymerase)

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8
Q

What are the 4 types of polymerases?

A

DdDp, DdRp, RdDp, RdRp

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9
Q

What is DNA-dependent DNA polymerase?

A

replicates DNA

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10
Q

What is DNA-dependent RNA polymerase?

A

makes mRNA and other RNA transcripts (such as RNA primers)

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11
Q

What is RNA-dependent DNA polymerase?

A

reverse transcriptase; uses RNA as a template to make DNA

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12
Q

What is RNA-dependent RNA polymerase?

A

copies viral RNA genome

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13
Q

Which polymerases do eukaryotic cells NOT have? What does this mean for the virus?

A

ANY RNA-dependent polymerases (RdRp and RdDp) which means the virus needs to have genes to make RNA-dependent polymerases

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14
Q

Which polymerases do DNA viruses use?

A

host-cell DNA-dependent polymerases

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15
Q

Which polymerases do RNA viruses use?

A

need to have genes to make their RNA-dependent polymerases (can come with them)

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16
Q

What are segmented genomes?

A

genome is cut into 8 different pieces (segments)

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17
Q

What are gapped genomes?

A

part of the genome is single-stranded while rest of genome is double stranded

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18
Q

What are ambisense genomes?

A

has both a (+) strand and a (-) strand

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19
Q

What are genomes with cross-linked ends of dsDNA?

A

ends are cross-linked to each other = difficult to replicate/transcribe genome

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20
Q

What are 3 basic strategies that viruses use to replicate their genome and synthesize mRNA?

A

based on host DNA (will use same strategies host already uses to replicate DNA) | emulate host (need DNA polymerase = only present during cell division = virus need to jump start cell cycle) | viral genomes are not chromosomes so don’t have telomerase = need to fix that issue

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21
Q

Which type of viruses are more likely to cause cancer and why?

A

DNA virus, they need to jump-start and push cell cycle forward = causes cells to begin replicating (and may not stop)

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22
Q

What are 2 common types of dsDNA viruses?

A

Herpes and HPV

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23
Q

What is the first biosynthetic event dsDNA viruses undertake? The second?

A

1) make mRNA –> protein | 2) replicate genome (can be used to make more mRNA)

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24
Q

What are the polymerases that dsDNA viruses use?

A

DdDp and DdRp

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25
Q

Which type of virus has gapped dsDNA?

A

Hepadena virus

26
Q

What polymerases does this gapped-dsDNA virus use?

A

RdDp (RT), DdRp, DdDp

27
Q

What is the first biosynthetic event that gapped dsDNA viruses undertake?

A

repair and fill in the broken gaps of its genome –> mRNA –> protein

28
Q

What are common example(s) of gapped dsDNA viruses?

A

hepatitis viruses

29
Q

How do gapped dsDNA viruses replicate their genome?

A

dsDNA &raquo_space;> (+)ssRNA via DdRp &raquo_space;> (-)ssDNA via RT (RdDp) &raquo_space;> enzymes make it gapped dsDNA

30
Q

What are the 3 benefits to having a gapped DNA genome?

A

more resistant against host cell defenses, mutations = evolutionary advantage, may assist with assembly of virus

31
Q

What is the first biosynthetic even ssDNA viruses need to undertake?

A

need to become dsDNA first

32
Q

Why can’t you make mRNA with a ssDNA molecule?

A

DNA-dependent RNA polymerase ONLY recognize double-stranded molecules

33
Q

What are the polymerases that ssDNA viruses use?

A

DdDp and DdRp

34
Q

What are the 3 strategies that RNA viruses use to replicate their genome and make mRNA?

A

encode for RdRp (host cells don’t have this), use RdRp, RdRp is used to replicate genome and make mRNA

35
Q

Which type of virus is the most abundant and why? (RNA or DNA viruses?

A

RNA viruses because they are always changing as RNA is less stable than DNA

36
Q

What is a key enzyme that scientists use to target RNA viruses and why?

A

RdRp or RdDp because host cells don’t have this

37
Q

What is a common type of dsRNA virus?

A

rotavirus

38
Q

What is the first biosynthetic event dsRNA viruses undertake?

A

use RdRp to synthesize (-)ssRNA strand which will be then transcribed to mRNA by RdRp

39
Q

What polymerases do dsDNA viruses use?

A

RdRp

40
Q

How do dsRNA viruses replicate their genome?

A

encapsidate some newly synthesized mRNA in a vesicle and use RdRp to copy the second strand

41
Q

Why do dsRNA viruses need to encapsidate their mRNA in a vesicle to replicate their genome?

A

they are hiding from host-cell defenses since our cells have never seen dsRNA = once cell detects dsRNA it will destroy it asap

42
Q

Which type of virus can potentially be used to cure cancer?

A

dsRNA viruses

43
Q

Which type of RNA virus is the most abundant?

A

(+)ssRNA viruses

44
Q

What are common types of (+)ssRNA viruses?

A

Togavirus and Flavivirus

45
Q

What is the first biosynthetic event (+)ssRNA viruses undertake?

A

make protein IF genome/mRNA is ribosome ready

46
Q

What polymerases do (+)ssRNA viruses use?

A

RdRp

47
Q

How do (+)ssRNA viruses replicate their genome?

A

RdRp makes (-)ssRNA that serves as a template to make (+)ssRNA

48
Q

What is the first protein that (+)ssRNA will make?

A

RdRp

49
Q

What is a common type of (+)ssRNA w/DNA intermediate virus?

A

retroviruses = HIV

50
Q

What is the first biosynthetic event (+)ssRNA w/DNA intermediate viruses undertake?

A

reverse transcribe their (+)ssRNA to (-)ssDNA

51
Q

What enzyme copies the complementary strand of (-)ssDNA?

A

reverse transcriptase (RdDp)

52
Q

What enzyme(s) do (+)ssRNA w/DNA intermediate viruses use?

A

RdDp and DdRp

53
Q

How do (+)ssRNA w/DNA intermediate viruses replicate their genome?

A

uses newly synthesized mRNA as genome since they are (+)ssRNA (essentially)

54
Q

Do (+)ssRNA w/DNA intermediate viruses have to encode for the RdDp once they get into the cell or do they carry it with them?

A

carry it with them

55
Q

What is unique about (+)ssRNA w/DNA intermediate viruses and how do they do this?

A

insert their genome into our genome via integrase

56
Q

What are common types of (-)ssRNA viruses?

A

rhaboviruses = rabies

57
Q

What is the first biosynthetic pathway (-)ssRNA viruses undertake?

A

RdRp copies (-)ssRNA into (+)ssRNA

58
Q

What polymerases do (-)ssRNA viruses use?

A

RdRp

59
Q

Do (-)ssRNA viruses have to encode for the RdRp once they get into the cell or do they carry it with them? And why?

A

carry it with them since they are (-)ssRNA and it needs to be copied into (+)ssRNA; no way of making RdRp from (-)ssRNA

60
Q

How do (-)ssRNA viruses replicate their genome?

A

use RdRp to re-transcribe their newly synthesized mRNA to (-)ssRNA

Virology (23 decks)

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