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Virology > Virus Classification - DNA, RNA > Flashcards

Virus Classification - DNA, RNA Flashcards

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1
Q

Define obligate intracellular parasite

A

Growth and reproduction of this organism can only occur inside of host cells

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2
Q

A virus is an Obligate intracellular parasite (T/F)

A

True

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3
Q

What is viral genetic information surrounded by?

A

Protein in the form of protein capsid

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4
Q

Range of virus sizes

A

20-300nm

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5
Q

Viruses have a receptor - binding protein for attaching to cells (T/F)

A

True

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6
Q

Viruses are not host/organ specific (T/F)

A

False; viruses have host and organ specificity i.e. they can target specific organs in a host or specific hosts

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7
Q

Viruses cannot pass through filters (T/F)

A

False; viruses are ultramicroscopic unlike bacteria which can be filtered

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8
Q

Which microscope is used to observe viruses

A

Electron microscope

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9
Q

List 4 main components of a virus structure

A

Nucleic acid genome, protein capsid, lipid envelope, envelope proteins

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10
Q

Classifications of viruses based on nucleic acids

A

DNA viruses

RNA viruses

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11
Q

Herpes, Pox, Papovavirus, Parvovirus, Adenovirus, Bacteriophage
- These are DNA or RNA viruses?

A

DNA viruses

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12
Q

Herpes virus types

A

Human herpes virus 1 - Herpes Simplex Virus 1
“ “ “ 2 - HSV2
“ “ “ 3 - Varicella zoster virus - chicken pox
Human “ “ 4 - Epstein-Barr virus
Human “ “ 5 - Cytomegalovirus
“ “ “ 6
“ “ “ 7
“ “ “ 8 - Kaposi sarcoma associated herpes virus

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13
Q

Pox virus

A

Smallpox virus

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14
Q

Are antibiotics used when treating patients with viruses?

A

No; only if patient is in ICU and has secondary bacterial infection

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15
Q

Icosahedral - define

A

A polyhedron with 20 faces

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16
Q

Complex viral structure - define

A

Combination of icosahedral and helical shape and may have a complex outer wall or head-tail morphology e.g. bacteriophage

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17
Q

Enveloped viruses are only double stranded (T/F)

A

True

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18
Q

Name an icosahedral, ds, enveloped DNA virus

A

Herpes

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19
Q

Name a complex, ds, enveloped DNA virus

A

Pox

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20
Q

Naked viruses have no lipid envelope (T/F)

A

True

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21
Q

The structure of naked viruses consists of both complex and icosahedral (T/F)

A

False; all are icosahedral

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22
Q

Naked viruses are only single stranded (T/F)

A

False, both single and double stranded

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23
Q

Name an icosahedral, ss, naked DNA virus

A

Parvovirus

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24
Q

Name an icosahedral, ds, naked DNA virus

A

Papovavirus, Adenovirus

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25
Q

+ssRNA vs -ssRNA

A

a positive-sense RNA virus doesn’t need a polymerase (enzyme) and so the virus is able to make message for the DNA right away without a vital enzyme! It can make viral DNA immediately.
-ssRNA must be converted to +ssRNA before translation to make proteins because -ssRNA is complementary to mRNA.

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26
Q

ssRNA is split into +ve stranded and -ve stranded types of viruses (T/F)

A

True

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27
Q

Name a +ve stranded, ss, naked RNA virus

A

Picornavirus, Calicivirus

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28
Q

Name a +ve stranded, ss, enveloped RNA virus

A

Togavirus, Flavivirus, Coronavirus, Retrovirus

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29
Q

Name a virus that can be either +ve or -ve stranded but single stranded

A

Arenavirus

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30
Q

Name a -ve stranded, ss, enveloped RNA virus

A

Bunyavirus, Orthmyxovirus, Paramyxovirus, Rhabdovirus

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31
Q

Name a ds, naked RNA virus

A

Reovirus

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32
Q

Picorna, Calici, Toga, Flavi, Reovirus all are icosahedral and the rest of RNA viruses are helical (T/F)

A

True

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33
Q

Structure of naked capsid virus

A

DNA/RNA + Structural proteins +/- enzymes and nucleic acid binding proteins = nucleocapsid

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34
Q

Structure of enveloped virus

A

Nucleocapsid + Glycoproteins and membrane

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35
Q

Viruses have two protective layers (T/F)

A

True - protein and lipid layers

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36
Q

Function of capsid/ protein coat

A

– Protects nucleic acid from inactivation

– Helps to introduce viral genome into host cell

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37
Q

Capsid is composed of

A

Capsomers

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38
Q

Capsomer is composed of

A

Repeating protein subunits blocks that make up the capsid.

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39
Q

Protomers are ?

A

The polypeptide chains which make up the capsomers

40
Q

Icosahedral capsid symmetry

A

12 Corners & 20 Sides

  • Two types of Capsomers form the Capsid
  • Pentagonal capsomers form the vertices
  • Hexagonal capsomers form the sides
41
Q

Capsid symmetry - helical

A

Capsomers & nucleic acid are wound together to form a helical or spiral tube

42
Q

Complex capsid symmetry

A

The overall shape of virus is quite variable , but mostly they are spherical

43
Q

Protein subunits seen as projecting spikes on the

surface of envelope are called

A

Peplomers

44
Q

A virus may have more than one type of peplomer (T/F)

A

True

45
Q

Example of virus with more than one type of peplomer

A

Influenza virus

46
Q

Properties of peplomers

A
  • Confers chemical , antigenic & biological properties.

- Susceptible to lipid solvents

47
Q

Viral replication steps

A 
1) Recognition of host cell
 ↓
2) Attachment
 ↓
3) Penetration
 ↓
4)Uncoating
 ↓
5) Transcription ( RNA-dependent RNA transcriptase is carried with virus for -sense b/c needs to be converted to +sense mRNA to form proteins in nucleus)
 ↓
6) Protien synthesis
 ↓
7) Replication
 ↓
8) Assembly
 ↓
9) Lysis & release
48
Q

When is the eclipse phase of viral replication?

A

From the stage of penetration till the appearance of mature daughter virions
The virions cannot be detected inside the host cell

49
Q

Duration of eclipse phase

A

3-12 hours

50
Q

Viruses can grow on chemically defined media (T/F)

A

False

51
Q

Types of Arboviruses

A

Alpha virus
- Chikungunya

Flaviviridae
–> Mosquito transmission
Hemorrhagic group
- Yellow fever, Dengue

Rhabdovirus
- Rabies virus

52
Q

In vivo vs in vitro

A

In vivo - lab bred animals, embryonic bird tissue

In vitro - cell/tissue culture

53
Q

Why do we culture viruses?

A
  • Isolate + ID viruses
  • Research on viral structure, replication effects on host cell
  • Prepare virus for vaccine production
54
Q

How does animal culture work?

A

Animals are inoculated with the virus and observed for effects which can include death
Virus is isolated and purified from the tissue of these animals.

55
Q 
Match virus to animal inoculation (rabbit, monkey, white mouse, baby white mouse)
HSV 
Rabies virus
Dengue virus
Polio virus
A

HSV - rabbit
Rabies virus - white mouse
Dengue virus - baby white mouse
Polio virus - monkey

Animal inoculation isn’t done much anymore - difficulty in choosing animals + care

56
Q

Which viruses is CAM (chorioallantoic membrane) used for?

A

Herpes simplexx virus, Pox virus

57
Q

Which viruses is Amniotic cavity used for?

A

Inoculation is mainly done for primary isolation of influenza virus and the mumps virus.

58
Q

What is Amniotic cavity used for?

A

10 day old embryo

Inoculation is mainly done for production of vaccine of influenza virus, yellow fever, rabies.

59
Q

Which viruses is the yolk sac used for?

A

3-8 day old embryo

e.g.: Chlamydiae & Ricketssia

60
Q

Which viruses is the intraembryonal area used for?

A

Japanese B encephalitis virus

61
Q

Pros and cons of inoculating embryonated eggs

A

Pros
They are free from contaminating bacteria and many latent viruses.
Specific and non specific factors of defense are not involved in embryonated eggs
Cost effective and maintenance is much easier.

Cons
Site of inoculation for varies with different virus. That is, each virus have different sites for their growth and replication.
Primary cultures usually have a limited life span. When cells in a primary culture undergo mitosis and a sufficient density of cells is produced, cells come in contact with other cells.
When this cell-to-cell-contact occurs, mitosis is triggered to stop. This is called contact inhibition and it prevents the density of the cells from becoming too high.
To prevent contact inhibition, cells from the primary cell culture must be transferred to another vessel with fresh growth medium (secondary cell culture).

62
Q

Purpose of cell cultures in cultivating viruses

A

For isolation , Neutralization , Production of Antigen for

serological assay

63
Q

Types of cell cultures

A

Primary culture :- Made by dispersing cells from freshly
removed host tissues , unable to grow for more than a few passage/sub cultures.
eg : - Rhesus monkey kidney cell & Human
amnion cell culture .

Secondary / Diploid culture :- Diploid cell lines up to 50
passage/ sub cultures but retain their normal chromosome pattern.
eg Human embryonic lung cell culture.

Continuous cell line / Heteroploid cell culture :- Capable of prolonged , infinite growth , derived from cancerous cells ,
grow faster with haploid chromosomes.
eg HeLa cell from cancer of cervix , Hep-2 ( epithelioma of larynx cell ) .

64
Q

Pros and cons of cell cultures

A

Pros
Relative ease, broad spectrum, cheaper and sensitivity
Cons
Need trained technicians 24/7
Most hospital labs don’t isolate and ID viruses

65
Q

What are Cytopathic effects?

A

Cytopathic effects (CPEs) are distinct observable cell abnormalities due to viral infection.

66
Q 
Which of the following is NOT a cytopathic effect?
transformation
cell fusion
mononucleated cell
inclusion bodies
A

Mononucleated cell

67
Q

Cell abnormalities resulting from a viral infection are called _____________.

A

Cytopathic effects

68
Q

CPEs can include what events in a viral cell?

A

CPEs can include:

  • adherence of red blood cells to the surface of avirus (hemadsorption)
  • inhibition of viral reproduction (interference)
  • changes in cell shape from flat to round, shrinkage of the nucleus (transformation)
  • vacuoles in the cytoplasm, fusion of cytoplasmic membranes and the formation of multinucleated syncytia,
  • inclusion bodies in the nucleus or cytoplasm, and
  • complete cell lysis
69
Q

During viral replication, what can be produced?

A

Inclusion bodies

70
Q

Inclusion bodies become larger tan viruses and have an affinity for dyes (T/F)

A

True

71
Q

Intra vs inter

A

Intra - inside

Inter - between

72
Q

Herpes virus , Poliovirus , Echovirus , Coxsackie virus , Influenza virus , Rubella virus , CMV all have inclusion bodies present where in a viral cell?

A

Nucleus

73
Q

Herpes virus , Poliovirus , Echovirus , Coxsackie virus , Influenza virus , Rubella virus , CMV all have inclusion bodies present where in a viral cell?

A

Nucleus; if the virus is made of RNA then it affects cyotplasm and if DNA then nucleus, this is because inclusion bodies form during viral replication

74
Q

Herpes virus has inclusion bodies where in a viral cell?

A

Nucleus

75
Q

Influenza virus has inclusion bodies where in a viral cell?

A

Nucleus

76
Q

Poxvirus , Rabies virus has inclusion bodies where in a viral cell?

A

Cytoplasm

77
Q

Adeno virus & Measles virus has inclusion bodies where in a viral cell?

A

Both ( nucleus&cytoplasm)

78
Q

Cowdry bodies - define

A

Eosinophilic nuclear inclusions made up of nucleic acid and proteins

79
Q

Cowdry bodies - define

A

Eosinophilic nuclear inclusions in viruses, composed of nucleic acid and protein seen in cells infected with Herpes simplex virus

Nuclear inclusions - Abnormal substances in the nuclei

80
Q

Most viruses are acidophilic, few basophilic e.g. ______.

A

Adenovirus

81
Q

Intra nuclear inclusions consist of what types of inclusions?

A

Cowdry type A and cowdry type B

82
Q

Cowdry type A is found in?

A

Yellow fever - Variable size, granular appearance

83
Q

Cowdry type B is found in?

A

Polio) - Circumscribed (confined to one area) , multiple

84
Q

Match the Intra cytoplasmic inclusions to the viruses (Small pox, adenovirus, rabies, measles)
Guarnieri bodies
Negri bodies
Both

A 
Guarnieri bodies ( Small pox )
Negri bodies ( Rabies )
Both ( Measles , Adenovirus )
85
Q

Bacteriophage - define

A

Viruses that infect bacteria

86
Q

Shape of head and sheath of bacteriophage

A

Capsid ( head ) is polyhedral ,

Sheath is helical

87
Q

Bacteriophages can pass through bacterial filters (T/F)

A

True

88
Q

Bacteriophages have low host specificity

A

False; high host specificity

89
Q

Common habitat of bacteriophages

A

Intestinal tract of animals

90
Q

Bacteriophage purpose

A

Bacterial identification; not viral ID

91
Q

Phage typing - explain

A
  • Classify strains within species of bacteria, each strain is sensitive to a small number of different phages
  • Leaves patterns of growth and lysis that can determine the strain.
92
Q

Phage typing - purpose

A

Trace the source of outbreaks of infections.
—The viruses that infect bacteria are called bacteriophages and some of these can only infect a single strain of bacteria.

Act as carrier of genes from one bacterium to another

Utilized to study Host - Parasite Relationships

93
Q

Hemadsorption is used for?

Hemadsorption process

A

hemadsorption : adherence of red blood cells to the surface of something (as a virus or cell)

Testing presence of Influenza
Influenza virus - Orthomyxoviridae
- Has diff antigens on surface, one of which is HA (Hemagglutinin). Drop erythrocytes of guinea pig onto viral cell culture of Influenza to see if it will be absorbed by the cell surface antigens.

94
Q

Direct Immunofluorescence Assay (DIA)

A
  • Antibody tagged fluorescent dye on infected cells and view on fluorescent microscope
95
Q

ImmunoPeroxidase Staining

A
  • Immunoperoxidase staining the cells coated for viral antigens

immune protein called an antibody will attach itself to certain substances, called antigens, that are on or in the cell.

an antibody is joined to an enzyme, peroxidase, that catalyses a reaction in which the protein is specifically stained brown.

Virology (7 decks)

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