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Microbiology > Ch. 8 > Flashcards

Ch. 8 Flashcards

1
Q

Virus-

A

Genetic element that cannot replicate independently of a living (host) cell

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2
Q

Virology-

A

The study of viruses

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3
Q

Virus particle (virion)-

A

Extracellular form of a virus

  • exists outside host and facilitates transmission from one host cell to another
  • contains nucleic acid genome surrounded by a protein coat and, in some cases, other layers of material
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4
Q

Viral genomes-

A
  • either DNA or DNA genomes
  • some are circular, but most are linear
  • only one type of genomic nucleic acid is found in the virion
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5
Q

Viruses can be classified on the basis of what?

A

The hosts they infect

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6
Q

Viral hosts and taxonomy:

A
  • bacterial viruses (bacteriophages)
  • archaeal viruses
  • animal viruses
  • plant viruses
  • other viruses
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7
Q

Smallpox virus

A

One of the larger viruses (about 200nm in diameter)

The size of the smallest known bacterial cell

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8
Q

Poliovirus

A

One of the smallest viruses (28nm in diameter)

About the size of a ribosome

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9
Q

Most viruses are ___ than prokaryotic cells.

A

Smaller

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10
Q

Capsid-

A

The protein shell that surrounds the genome of a virus particle

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11
Q

The capsid is composed of..

A

A number of protein molecules arranged in a precise and highly repetitive pattern around the nucleic acid

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12
Q

Capsomere-

A

Subunit of the capsid (individual protein molecules)

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13
Q

What is the smallest morphological unit visible with an electron microscope?

A

Capsomere

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14
Q

___ is a single-stranded RNA virus.

A

TMV

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15
Q

TMV causes disease in ..

A

Tobacco, tomato, and related plants

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16
Q

Nucleocapsid-

A

Complete complex of nucleic acid and protein packaged in the virion

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17
Q

Enveloped virus-

A

Virus that contains additional layers around the nucleocapsid

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18
Q

___ are constructed in highly symmetric ways.

A

Nucleocapsids

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19
Q

Helical symmetry-

A

Rod-shaped viruses

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20
Q

Length of virus is determined by..

A

Length of nucleic acid

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21
Q

Width of virus determined by..

A

Size and packaging of protein subunits

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22
Q

Icosahedral symmetry-

A

Spherical viruses

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23
Q

Example of a virus with icosahedral symmetry

A

Human papilloma virus

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24
Q

Human papilloma virus

A

Genital warts and cervical cancer

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25
Q

What is the most efficient arrangement of subunits in a closed shell?

A

Icosahedral symmetry

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26
Q

Enveloped virus-

A

Have membrane surrounding nucleocapsid

- lipid bilayer with embedded proteins

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27
Q

___ makes initial contact with host cell.

A

Envelope

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28
Q

Envelope originates from host __ __.

A

Cytoplasmic membrane

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29
Q

Some virions contain enzymes critical to ___.

A

Infection

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30
Q

Lysozyme-

A
  • makes hole in cell wall
  • lyses bacterial cell
  • bacteriophages
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31
Q

Neuraminidases-

A
  • enzymes that cleave glycosidic bonds
  • destroys animal cell connective tissue
  • allows liberation of viruses from cell
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32
Q

Phases of viral replication:

A
  • attachment (absorption)
  • entry (penetration)
  • synthesis
  • assembly
  • release
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33
Q

Phases of viral replication

Attachment (absorption) of..

A

The virus to a susceptible host cell

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34
Q

Phases of viral replication

Entry (penetration) of..

A

The virion or its nucleic acid

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35
Q

Phases of viral replication

Synthesis of..

A

Virus nucleic acid and protein by cell metabolism as redirected by virus

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36
Q

Phases of viral replication

Assembly of..

A

Capsids and packaging of viral genomes into new virions (maturation)

37
Q

Phases of viral replication

Release of..

A

Mature virions from host cell

38
Q

Virus replication is typically characterized by a ___ ___ ___.

A

One-step growth curve

39
Q

Latent period-

A

Eclipse + maturation

40
Q

Burst size

A

Number of virions released

41
Q

How long do bacterial viruses take to replicate?

A

20-60 mins

42
Q

How long do animal viruses take to replicate?

A

8-40 hours

43
Q

___ replicate only in certain types of cells or in whole organisms.

A

Viruses

44
Q

___ viruses are easiest to grow.

A

Bacterial

Model system

45
Q

___ viruses can be cultivated in tissue or cell cultures.

A

Animal

46
Q

___ viruses are typically most difficult because study often requires growth of the whole plant.

A

Plant viruses

47
Q

Titer-

A

Number of infectious units per volume of fluid

48
Q

Plaque assay-

A

Analogous to the bacterial colony; one way to measure virus infectivity

49
Q

Plaques-

A

Clear zones that develop on lawns of host cells

50
Q

___ ___ is used in quantitative virology.

A

Plating efficiency

51
Q

Permissive cell-

A

Host cell that allows the complete replication cycle of a virus to occur

52
Q

Bacteriophage T4

A
  • virus of E. coli

- one of the most complex penetration mechanisms

53
Q

Restriction modification systems-

A

DNA destruction system

Effective only against double-stranded DNA viruses

54
Q

Restriction enzymes-

A

Cleve DNA at specific sequences

55
Q

Glycosylation-

A

Glucose attached to a hydroxyl

56
Q

Methylation-

A

Addition of a methyl group

57
Q

T4 genome can be divided into three parts:

A

Early proteins
Middle protein
Late proteins

58
Q

Early and middle proteins:

A

Enzymes needed for DNA replication and transcription

59
Q

Late proteins-

A

Head and tail proteins and enzymes required to liberate mature phase particles

60
Q

Production of early proteins

A
  • enzyme for the synthesis and glucosylation of the T4 base hydroxymethylcytosine
  • enzymes that function in T4 replisome
  • proteins that modify host rna polymerse
61
Q

Production of middle proteins

A

Additional proteins that modify host rna polymerase

62
Q

Production of late proteins

A
  • synthesized later
  • include proteins of virus coat
  • typically structural components
  • synthesized in larger amounts
63
Q

Virulent mode-

A

Viruses lyse host cells after infection

64
Q

Temperate mode-

A

Viruses replicate their genomes in tandem with host genome without killing the host

65
Q

Temperate viruses-

A

Can undergo a stable genetic relationship within the host

66
Q

Lysogeny-

A

State where most virus genes are not expressed and virus genome is replicated in synchrony with host chromosomes

67
Q

Lysogen-

A

A bacterium containing a prophage

68
Q

Packaging the T4 genome

A
  • precursor of bacteriophage head is assembled
  • packaging motor is assembled
  • double-stranded DNA is pumped into head under pressure using ATP
  • after head is filled with DNA, T4 tail, tail fibers, and other components are added
69
Q

Bacteriophage lambda

A
  • linear, dsDNA genome

- complementary, single-stranded regions 12 nucleotides long at the 5’ terminus of each strand

70
Q

When it enters lytic pathway, lambda synthesizes long, linear concatemers of DNA by ___ ___ ___.

A

Rolling circle replication

71
Q

Regulation of lytic vs lysogenic events in lambda is controlled by a complex ___ ____.

A

Genetic switch

72
Q

cl protein (the lambda repressor)-

A

Causes repression of lambda lytic events

73
Q

Cro repressor-

A

Controls activations of lytic events

74
Q

Most phases contain ___ genomes.

A

dsDNA

75
Q

Persistent infections-

A

Release of virions from host cell does not result in cell lysis

76
Q

Latent infections-

A

Delay between infection by the virus and lytic events

77
Q

Transformation-

A

Conversion of normal cell into tumor cell

78
Q

Cell fusion-

A

Two or more cells become one cell with many nuclei

79
Q

Retroviruses -

A

RNA viruses that replicate through a DNA intermediate

80
Q

Gag-

A

Encode structural proteins

81
Q

Pol-

A

Encode reverse transcriptase and integrase

82
Q

Env-

A

Encode envelope proteins

83
Q

Process of replication of a retrovirus:

A
  • entrance into the cell
  • removal of virion envelope at the membrane
  • reverse transcription of one of the two RNA genomes
  • integration of retroviral DNA info host genome
  • transcription of retroviral DNA
  • assembly and packaging of genomic RNA
  • budding of enveloped virions; release from cell
84
Q

About how many prokaryotes per ml of seawater?

A

10^6

85
Q

About how many viruses per ml of seawater?

A

10^7

86
Q

___ thought to have a major impact on evolution of bacteria.

A

Bacteriophages

87
Q

Most of earths genetic diversity resides in ___.

A

Viruses

88
Q

Most viruses are believed to be ___.

A

Bacteriophages

Microbiology (26 decks)

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