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LIFE 3007 > Properties of Viruses: Structure and Fundamentals of Viral Replication > Flashcards

Properties of Viruses: Structure and Fundamentals of Viral Replication Flashcards

1
Q

Define Peptide

A

two or more amino acids linked together by a peptide bond

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2
Q

Define oligopeptide

A

a short peptide, 5-20 amino acids

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3
Q

Define polypeptide

A

extended peptide of undefined length 20+ amino acids

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4
Q

What is polymerase

A

proteins involved in replication by creating a complementary strand of DNA or RNA from a template molecule

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5
Q

What is mRNA

A

the template for protein translation with positive sense polarity and a 5’ cap and 3’ poly-A tail

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6
Q

Define Positive Sense

A

A positive sense DNA or RNA molecule is one where the genes are encoded in a form that is directly translated to the protein.

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7
Q

Define negative sense

A

Negative sense DNA or RNA molecule is one where the genes are encoded in the reverse complement of the protein coding version

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8
Q

Viral genomes can be encoded on a single molecule and known as

A

non-segmented

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9
Q

Viral genomes can be encoded on several different molecules and are known as

A

segmented

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10
Q

What is a virus/virion mainly comprised of

A
  1. Nucleic acid
  2. A protein shell/capsid
  3. Lipid envelope derived from host membrane (some viruses)
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11
Q

List of structural proteins in viruses

A
  1. Surface proteins: Hemagglutinin envelope of influenza A (IAV), VP7 of rotaviruses, gp120 of HIV
  2. Ion channels: M2 of IAV
  3. Capsid and matrix proteins : VP1-VP4 of rhinoviruses
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12
Q

List of non-structural proteins in viruses

A
  1. Enzymatic Functions
  2. Cellular Pathway disruptors
  3. Immunomodulators
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13
Q

Three examples of Enzymatic functions in virions

A
  1. for copying viral genome reverse transcriptase enzyme (e.g HIV)
  2. Proteases are used to cleave viral proteins (e.g FMDV 2a protein, NS3/4A of hepatitis C)
  3. Modifying enzymes (e.g heparinase enzyme of herpes simplex virus 2
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14
Q

Group 1 viruses are _______ stranded _NA viruses which replicate in the ___________ using cellular proteins or in the __________ and make their own enzymes for _________ ________ ___________.

A

double
DNA
nucleus
cytoplasm
nucleic acid replication

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15
Q

Give four examples of group 1 viruses

A
  1. Adenovirus from adenoviridae
  2. Herpesvirus from Herpesviridae
  3. Papillomavirus from papovaviridae
  4. Molluscum contagiosum from Poxviridae
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16
Q

Group 2 viruses are ___________ stranded _NA viruses. Their replication takes place in the ___________ and involves the formation of a ________ sense strand which serves as a template for the __________ strand RNA and DNA synthesis

A

single
DNA
nucleus
negative
positive

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17
Q

Give an example of a group 2 virus

A

Parvoviridae which causes the parvovirus B19

18
Q

Group 3 viruses are _______________ stranded _NA viruses. Their genomes can be both ____________ and ___________________ as well as _____________ or ____________. There replication does not include a ______ phase

A

double
RNA
non-segmented
segmented
linear
circular
DNA

19
Q

Give an example of a group 3 virus

A

Reoviridae responsible for the human rotavirus

20
Q

Group 4 viruses are _____________ sense ___________ stranded _NA viruses. Their genomes can be both ____________ and _________________. Genomes act as a _____________ template for translation meaning the genome is equivalent to mRNA. Their protein generates a _____________ and all the proteins are translated simultaneously.
The genome of group 3 viruses must encode RNA dependent ___________ polymerase enzyme (_____) and its replication does not include a ___________ phase

A

positive
single
non-segmented
segmented
direct
polyprotein
RNA
RdRp
DNA

21
Q

What are two examples of group 4 viruses

A

Coronaviridae responsible for corona virus

Picornaviridae reponsible for Hep A

22
Q

Group five viruses are ___________ sense ___________ stranded _NA viruses. Their first step in replication is the production of ________ and the _______ act as a template for mRNA synthesis. Their replication cycle does not include a ______ phase.

A

negative
single
RNA
mRNA
genome
DNA

23
Q

Give two examples of a group 5 viruses

A

Paramyxoviridae which is responsible for measles

Filoviridae which is responsible for the ebola virus

24
Q

Group 6 viruses are ____________-transcribing ___________ sense, ________ stranded _NA viruses. Their genomes are ______________ but the virion may contain multiple copies. The genome must encode for _______ dependent DNA polymerase ( ) enzyme also known as reverse transcriptase. The first step in replication is production of _______ stranded _NA

A

reverse
positive
single
RNA
non-segmented
RNA
RdDp
double
DNA

25
Q

Give an example of a group 6 virus

A

Retroviridae which causes HIV

26
Q

What is an example of group 7 virus

A

Hepadnaviridae which causes Hepatitis B virus

27
Q

Define taxonomy

A

the hierarchy of virus classification

28
Q

Which committee is responsible for classifying viruses?

A

International Committee on the taxonomy of viruses (ICTV)

29
Q

The primary criteria for classification of viruses is

A

pairwise sequence identity comparisons

30
Q

Other than pairwise sequence identity what other criteria is used to classify bacteria?

A

Genome composition
Virus capsid structure
Whether the virus is enveloped or not
The mechanism of gene expression
Tropism
Pathogenicity

31
Q

Define tropism

A

The point of entry via interactions between virus surface proteins and host cell molecules

32
Q

The three types of tropism

A

host
cellular
tissue

33
Q

What are the steps taken in virus replication

A
  1. Attachment
    2 Entry
  2. Uncoating
  3. Genome Replication and production mRNA (transcription)
  4. Production of protein (translation)
  5. Particle assembly
  6. Virion release (egress) and virion maturation in some viruses
34
Q

Describe the attachment step in virus replication

A
  • a protein on the surface of the virus binds to a receptor on the surface of host cell in accordance with its tropism
35
Q

Describe the entry step in virus replication

A

-As the cell membrane is impermeable the virus cannot diffuse across the cell and uses types of facilitated entry like plasma membrane membrane fusion and endocytosis

36
Q

Describe the uncoating process in virus replication

A

-This is when the virus genome is exposed to the intracellular environment of he host cell in the nucleus or cytoplasm depending on the virus
- During this stage there ma be a small change to the genome or a complete disintegration of the virion.
- Uncoating may occur at the same time as entry where the genome and other associated proteins are deposited inside

37
Q

Describe the protein production process of virus replication (translation)

A

-some viruses synthesis their protien as a single continuous chain from a single mRNA with one start codon
-these are cleaved post translation by protease and release the individual mature proteins (Flaviviruses)
- post translational modifications like glycosylation, myristylation and the addition of a gpi anchor is common

38
Q

An example of a virus that regulates the timing of translation to control their cellular environment when replicating

A

Herpesviruses

39
Q

Describe the particle assembly process of viral replication

A

-New virions are assembled with all structural proteins and their genome
- Occurs in various locations depending on the virus

40
Q

Describe the egress and maturation process in viral replication

A

-new virions are released from the host cell in a manner that is specific to the virus
-there is then complete cellular breakdown of the host cell
-there is then budding of the cell before it fully dies
-the bud then exits through exocytosis and moves on to infect the rest of the body

LIFE 3007 (6 decks)

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