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BMSC 210 > Chapter 8 - Viruses and Their Replication > Flashcards

Chapter 8 - Viruses and Their Replication Flashcards

1
Q

archaea viruses

A
  • great diversity

- major role in oceanic microbiomes

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2
Q

How do archaea viruses differ from eukaryotic and bacterial viruses?

A

in genome, morphology, architecture, proteins encoded

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3
Q

virus

A

genetic element that cannot replicate independently of a living host cell

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4
Q

virology

A

study of viruses

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5
Q

virus particle/virion

A

extracellular form of a virus

-exists outside host and facilitates transmission from one host cell to another

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6
Q

virion make up

A

nucleic acid genome surrounded by a protein coat and, in some cases, other layers of material (phospholipid membrane with viral glycoproteins)

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7
Q

characteristics of viruses

A
  • infectious, acellular patheogens
  • obligate intracellular parasites with host and cell-type specificity
  • DNA of RNA genome; never both
  • lack genes for reproduction, requiring exploitation of host-cell genomes to reproduce
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8
Q

Viral genomes are sometimes circular, but most..

A

linear

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9
Q

RNA viruses that contain ________ can be directly read by ribosomes to synthesize viral proteins.

A

+ssRNA

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10
Q

Viruses containing _______ must use the _______ template for the synthesis of _______ before viral proteins can be made.

A

-ssRNA, -ssRNA, +ssRNA

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11
Q

+ssRNA

A

positive single strand RNA

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12
Q

-ssRNA

A

negative single strand RNA

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13
Q

Viruses can be classified on the basis of…

A

the host they infect

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14
Q

New classification schemes call for classification of viruses based on…

A

nucleic acid similarities

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15
Q

viruses sizes

A

usually smaller than prokaryotic cells at 0.02 to 0.3 um

-most viral genomes smaller than those of cells

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16
Q

capsid

A

the protein shell that surrounds the genome of a virus particle

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17
Q

capsid composition

A

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

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18
Q

capsomere

A

subunit of the capsid

-smallest morphological unit visible with an electron microscope

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19
Q

nucleocapsid

A

complete complex of nucleic acid and protein packaged in the virion

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20
Q

enveloped virus

A

virus that contains additional layers around the nucleocapsid (lipid bilayer with embedded proteins)
-envelop makes initial contact with host cell

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21
Q

arrangement of nucleic acid and protein coat in a simple virus

A

RNA assumes a helical configuration surrounded by the protein capsid
-center is hollow

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22
Q

In ro-shaped viruses, length is determined by…. and width is determine by….

A

length: length of nucleic acid
width: size and packaging of protein subunits

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23
Q

icosahedral symmetry

A

spherical viruses

-most efficient arrangement of subunits in a closed shell

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24
Q

influenza virus envelope

A

contains “spikes” of hemagglutinin and neuraminidase forming a halo of projections around negatively stained virus particles

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25
Q

ebola virion composition

A
  • helical
  • spikes of envelope
  • lipid envelope
  • membrane associated proteins
  • nucleocapsid proteins
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26
Q

If a virion has a ____________, they might infect humans.

A

lipid envelope

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27
Q

complex viruses composition

A

several parts, each with separate shapes and symmetries

-icosahedral head and helical tails

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28
Q

Most phages contain _____ genomes

A

dsDNA (double stranded)

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29
Q

Enzymes in virions critical to infection

A
  • lysozyme-like
  • nucleic acid polymerases
  • neuraminidases
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30
Q

lysozyme-like enzymes

A
  • make hole in cell wall

- lyses bacterial cell in later stages of infection to release new virions

31
Q

nucleic acid polymerases

A

-for replication of the viral genome and for transcription of virus specific RNA

32
Q

neuraminidases

A

surface protein

-enzymes that cleave glycosidic bonds and allowing liberation of viruses from cell

33
Q

What is used to culture human or animal viruses?

A

flasks

34
Q

viruses replicate only in…

A

certain types of CELLS or in WHOLE ORGANISMS

35
Q

What kind of viruses are the easiest to grow?

A

bacterial; model systems

36
Q

titer

A

number of infectious units per volume of fluid

37
Q

plaque assay

A

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

38
Q

plaques

A

clear zones that develop on lawns of host cells

  • lawn can be bacterial or tissue culture
  • each plaque results form infection by a single virus particle
39
Q

efficiency of plating

A

used in quantitative virology

40
Q

Number of plaque-forming units is almost aways lower that direct count due to…

A
  • inactive virions

- conditions not appropriate for infectivity

41
Q

phases of viral replication

A
  • attachment/adsorption
  • entry/penetration
  • synthesis
  • assembly/maturation
  • release
42
Q

latent period

A

eclipse + maturation; newly synthesized virions have not yet appeared outside the cell

43
Q

burst size

A

number of virions released

44
Q

lambda bacteriophage of e.coli

A
  • structure: head and tail
  • genome: dsDNA
  • linear
  • size of genome: 48500
45
Q

MS2 bacteriophage of e. coli

A

icosahedral

  • ssRNA
  • linear
  • 3600
46
Q

T7 and T3 bacteriophage of e. coli

A

head and tail

  • dsDNA
  • linear
  • 40000
47
Q

Attachment of virion to host cell is..

A

highly specific

48
Q

permissive cell

A

host cell that allows the complete replication cycle of a virus

49
Q

T4 attached to cells via..

A

tail fibers that interact with polysaccharides on the E. coli cell envelope

50
Q

Attachment of virus to its host cell results in ..

A

changes to both virus and cell surface that facilitate penetration

51
Q

mechanisms to diminish viral infections in eukaryotes and prokaryotes

A
  • immune defense mechanisms (RNA interference)

- restriction modification systems

52
Q

restriction modification systems

A
  • only effective against dsDNA viruses

- modification of hosts’ own DNA at RE recognition sites prevent cleavage of its DNA

53
Q

mechanisms to diminish viral infections in bacteria

A
  • chemical modification of viral DNA (glycosylation or methylation)
  • production of proteins that inhibit host cell RE system
54
Q

5-hydroxymethylcytosine

A

DNA resistant to virtually all known restriction enzymes

-modified base in T4 DNA

55
Q

T4

A

-dsDNA genome
-circularly permuted
-terminally redundant
(last 2 factors affect genome packaging)

56
Q

T4 genome can be divided into what 3 parts?

A

early, middle, and late proteins

57
Q

early and middle proteins

A

enzymes needed for DNA replication and transcription

58
Q

late proteins

A

head and tail proteins and enzymes required to liberate mature phage particles

59
Q

packaging of T4 genome

A
  • precursor of bacteriophage head is assembled
  • packaging motor is assembled
  • dsDNA is pupes into head under pressure using ATP
  • T4 tail, tail fibers, and other components added
60
Q

virulent mode

A

viruses lyse host cells after infection

61
Q

temperate mode

A

viruses replicate their genomes in tandem with host genome and without killing host
-virus can also be lytic

62
Q

lysogeny

A

state where most virus genes are not expressed and virus genome is replicated in synchrony with host chromosome

63
Q

prophage

A

virus genome

64
Q

lysogen

A

a bacterium containing a prophage

65
Q

animal virus infection stages

A
  • attachment
  • penetration
  • uncoating
  • release
  • assembly
  • biosynthesis
66
Q

influenza

A
  • influenza A virus
  • negative ssRNA
  • 13600
67
Q

acquired immunodeficiency syndrome (AIDS)

A
  • virus: human immunodeficiency virus (HIV)
  • ssRNA/dsDNA positive
  • 9700
68
Q

ebola hemorrhagic fever

A
  • ebola virus
  • ssRNA neg
  • 19000
69
Q

severe acute respiratory syndrome (SARS)

A
  • SARS virus
  • ssRNA pos
  • 29800
70
Q

persistent infections

A

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

  • can be latent of chronic
  • infected cell remains alive and continues to produce virus
71
Q

latent infections

A

delay between infection by the virus and lytic event

72
Q

transformation

A

conversion of normal cell into tutor cell

73
Q

cell fusion

A

two or more cells become one cell with many nuclei

74
Q

replication of retovirus

A
  • entry and uncaring of retrovirus
  • reverse transcriptase
  • viral DNA enters nucleus and integrates into host genome
  • transcription by host RNA pol forms viral mRNA and genome copies
  • translation of mRNA forms viral protein; new nucleocapsids assembled and released by budding

BMSC 210 (15 decks)

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