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Micobiology > Chapter 6 - The Search for the Elusive Virus > Flashcards

Chapter 6 - The Search for the Elusive Virus Flashcards

1
Q

Who postulated that rabies was caused by a virus (1884)

A

Louis Pasteur

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2
Q

Who showed a disease in tobacco was caused by a virus (1890s)

A

Ivanovski and Beijerinck

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3
Q

1950s ________ was a multifaceted discipline

A

Virology

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4
Q

Noncellular particles with a definite size, shape, and chemical composition

A

Viruses

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5
Q

There is no universal agreement on how and when _______ originated

A

Viruses

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6
Q

Viruses are considered the ____ ________ microbes on earth

A

Most abundant

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7
Q

Viruses played a role in _________of Bacteria, Archaea, and Eukarya

A

Evolution

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8
Q

Viruses are ________ ____________ parasites

A

Obligate intracellular

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9
Q

Most viruses are less than _____

A

0.2 μm

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10
Q

Viruses require an ________ __________ to see

A

Electron microscope

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11
Q

Viruses bear no resemblance to _____

A

Cells

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12
Q

Viruses lack _______ ____________ machinery

A

Protein-synthesizing

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13
Q

Viruses contain only the parts needed to ______ and _______ a host cell

A

Invade and control

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14
Q

All viruses have _______

A

Capsids

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15
Q

Protein coats that enclose and protect their nucleic acid

A

Capsids

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16
Q

The capsid together with the nucleic acid is the:

A

Nucleocapsid

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17
Q

Some viruses have an external covering called the:

A

Envelope

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18
Q

Those lacking an envelope are

A

Naked

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19
Q

Each capsid is constructed from identical subunits called:

A

Capsomers

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20
Q

What are capsomers made of?

A

Protein

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21
Q

What are the two structural types of viruses?

A
  1. Helical

2. Icosahedral

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22
Q

Continuous helix of capsomers forming a cylindrical nucleocapsid

A

Helical

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23
Q
  • 20-sided with 12 corners
  • Vary in the number of capsomers
  • Each capsomer may be made of 1 or several proteins
  • Some are enveloped
A

Icosahedral

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24
Q
  • Mostly animal viruses
  • Acquired when the virus leaves the host cell
  • Exposed proteins on the outside of the envelope, called spikes, essential for attachment of the virus to the host cell
A

Viral envelope

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25
Q
  • Protects the nucleic acid when the virus is outside the host cell
  • Helps the virus to bind to a cell surface and assists the penetration of the viral DNA or RNA into a suitable host cell
A

Capsid/Envelope

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26
Q

Complex viruses

A

Atypical viruses

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27
Q
  • Poxviruses lack a typical capsid and are covered by a dense layer of lipoproteins
  • Some bacteriophages have a polyhedral nucleocapsid along with a helical tail and attachment fibers
A

Complex viruses: atypical viruses

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28
Q

Either DNA or RNA but never both

A

Viral genome

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29
Q

Carries genes necessary to invade host cell and redirect cell’s activity to make new viruses

A

Nucleic Acids

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30
Q

Number of genes varies for each type of virus - ___ to ________

A

Few to hundreds

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31
Q

__________ enzymes may be present

A

Pre-formed

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32
Q

DNA or RNA

A

Polymerases

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33
Q

Copy RNA

A

Replicases

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34
Q

Synthesis of DNA from RNA (AIDS virus)

A

Reverse transcriptase

35
Q

Main criteria presently used for viruses are _________, ________ ___________, and _______ ______

A

Structure, chemical composition, and genetic makeup

36
Q

How many orders are there of viruses?

A

3

37
Q

How many families are there of viruses?

A

63

38
Q

How many genera are there of viruses?

A

263

39
Q

Family name of viruses ends in:

A

viridae

- ex: Herpesviridae

40
Q

Genus name of viruses ends in:

A

virus

- ex: Simplexvirus

41
Q

General phases in animal virus multiplication cycle

A
  1. Adsorption
  2. Penetration
  3. Uncoating
  4. Synthesis
  5. Assembly
  6. Release
42
Q

What is host range?

A

Spectrum of cells a virus can infect

43
Q

Flexible cell membrane is penetrated by the whole virus or its nucleic acid by:

A
  • Endocytosis

- Fusion

44
Q

Entire virus is engulfed and enclosed in a vacuole or vesicle

A

Endocytosis

45
Q

Envelope merges directly with membrane resulting in nucleocapsid’s entry into cytoplasm

A

Fusion

46
Q

DNA viruses generally are replicated and assembled in the _______

A

Neculeus

47
Q

RNA viruses are generally replicated and assembled in the _________

A

Cytoplasm

48
Q

Positive-sense RNA contain the message for ___________

A

Translation

49
Q

Negative-sense RNA must be converted into ________ _____ _______

A

Positive-sense message

50
Q

Assembled viruses leave host cell in one of two ways:

A

Budding or lysis

51
Q

Exocytosis; nucleocapsid binds to membrane which pinches off and sheds the viruses gradually; cell is not immediately destroyed

A

Budding

52
Q

Nonenveloped and complex viruses released when cell dies and ruptures

A

Lysis

53
Q

Number of viruses released is variable
3,000-4,000 released by _______
>100,000 released by __________

A
  • Poxvirus

- Poilovirus

54
Q

Virus-induced damage to cells

A

Cytopathic effects

55
Q

What are cytopathic effects?

A
  1. Changes in size and shape
  2. Inclusion bodies
  3. Cells fuse to form multinucleated cells
  4. Cell lysis
  5. Alter DNA
  6. Transform cells into cancerous cells
56
Q

Cell harbors the virus and is not immediately lysed

A

Persistent infections

57
Q

Can last weeks or host’s lifetime; several can become reactivated periodically

A

Chronic latent state

58
Q

Some animal viruses enter host cell and permanently alter its genetic material resulting in cancer. What is this called?

A

Transformation of the cell

59
Q

Transformed cells have increased rate of growth, alterations in chromosomes, and capacity to divide for indefinite time periods resulting in ______

A

Tumors

60
Q

Mammalian viruses capable of initiating tumors are called ___________

A

Oncoviruses

61
Q

Papillomavirus

A

Cervical cancer

62
Q

Epstein-Barr virus

A

Burkitt’s lymphoma

63
Q

Bacterial viruses (phages)

A

Bacteriophages

64
Q

Most widely studied are those that infect ___________ ____ - complex structure, DNA

A

Escherichia coli

65
Q

Multiplication goes through similar stages as animal viruses but _________ of nucleic acid upon entry into the host is not necessary

A

Uncoating

66
Q

Release is a result of cell lysis induced by viral enzymes and accumulation of viruses

A

Lytic cycle

67
Q

What are the 6 steps in phage replication?

A
  1. Adsorption
  2. Penetration
  3. Replication
  4. Assembly
  5. Maturation
  6. Release
68
Q

Results in the spread of the virus without killing the host cell

A

Lysogeny

69
Q

Phage genes in the bacterial chromosome can cause the production of toxins or enzymes that cause pathology

A

Lysogenic conversion

70
Q

What are temperate phages?

A
  • Prophage
  • Lysogeny
  • Induction
71
Q

Obligate intracellular parasites that require appropriate cells to replicate

A

Animal viruses

72
Q

What are the methods used to identify animal viruses?

A
  • Cell (tissue) cultures
  • Bird embryos
  • Live animal inoculation
73
Q

Viruses are the most common cause of _____ __________

A

Acute infections

74
Q

There are several _______ viral infections per year

A

Billion

75
Q

Some viruses have high _________ rates

A

Mortality

76
Q

There are possible connections of viruses to _______ ____________ of unknown cause

A

Chronic afflictions

77
Q

Viruses are major participants in the earth’s _________

A

Ecosystem

78
Q

Misfolded proteins, contain no nucleic acid

A

Prions

79
Q

Extremely resistant to usual sterilization techniques

A

Prions

80
Q
  • Cause transmissible spongiform encephalopathies – fatal neurodegenerative diseases
  • Common in animals
A

Prions

81
Q

Dependent on other viruses for replication

A

Satellite viruses

82
Q

Replicates only in cells infected with adenovirus

A

Adeno-associated virus

83
Q

Naked strand of RNA expressed only in the presence of hepatitis B virus

A

Delta agent

84
Q

Short pieces of RNA, no protein coat; only been identified in plants

A

Viroids

Micobiology (15 decks)

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