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Microbiology > Ch. 9 > Flashcards

Ch. 9 Flashcards

1
Q

Smallest s.s. DNA virus:

A

Circovirus 1.75 kilobase

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2
Q

Largest d.s. DNA virus:

A

Megavirus 1.25 megabase pairs

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3
Q

RNA viruses are typically ___ than DNA viruses.

A

Smaller

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4
Q

Circovirus

A

Smallest s.s. DNA virus

1.75 kilobase

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5
Q

Megavirus

A

Largest d.s. DNA virus

1.25 megabase pairs

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6
Q

Viral genomes are either ___ or ___ genomes.

A

DNA or RNA

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7
Q

Some viral genomes are circular, but most are ___.

A

Linear

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8
Q

The Baltimore Scheme

A

Virus classification based on the relationship of the viral genome to its mRNA and recognizes seven classes of viruses

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9
Q

What is the virus classification based on the relationship of the viral genome to its mRNA and recognizes seven classes of viruses?

A

The Baltimore scheme

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10
Q

Single stranded genome can be either a ____ virus or ___ virus.

A

Positive-strand virus (plus-strand virus)

Negative-strand virus (minus-strand virus)

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11
Q

Viral ___ is considered to be the plus strand.

A

mRNA

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12
Q

Viral mRNA is considered to be the ___ strand.

A

Plus

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13
Q

A phylogenetic tree has been constructed for ___ ___ ___ ___.

A

Nucleocytoplasmic large DNA viruses (NCLDV)

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14
Q

Most viral genes from nature have unknown ___.

A

Function

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15
Q

What bacteriophages contain single-stranded DNA genomes of the plus configuration?

A

Phi X174 and M13

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16
Q

Phi X174 and M13

Transcription of the genome is proceeded by synthesis of a ..

A

Complementary strand of DNA

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17
Q

Bacteriophage phi X174

A
  • contains a circular single-stranded DNA genome inside an icosahedral virion
  • very small genome with overlapping genes
  • replication occurs via rolling circle replication
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18
Q

How does replication occur in phi X174?

A

Rolling circle replication

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19
Q

Bacteriophage M13

A
  • model filamentous bacteriophage
  • used as a cloning and DNA-sequencing vector in genetic engineering
  • can be released without lysing host via a process called budding
  • viral infection slows host growth
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20
Q

___ is the model filamentous bacteriophage.

A

M13

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21
Q

Bacteriophage ___ is used as a cloning and DNA-sequencing vector in genetic engineering.

A

M13

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22
Q

Bacteriophage M13 can be released without lysing a host via a process called ___.

A

Budding

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23
Q

Single-stranded DNA bacteriophages:

A

Phi X174 and M13

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24
Q

Double-stranded DNA bacteriophages:

A

T7 and Mu

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25
Q

Bacteriophage T7

A
  • infects E. coli
  • virion has an icosahedral head and a very short tail
  • genome always enters host cell in same orientation
  • order of genes on the T7 chromosome influences regulation of virus replication
  • DNA replication employs T7 DNA polymerase and involves terminal repeats and the formation of concatemers
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26
Q

Bacteriophage T7

Order of genes on the T7 chromosome influences regulation of ___ ___.

A

Virus replication

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27
Q

DNA replication employs T7 DNA polymerase and involves terminal repeats and the formation of ___.

A

Concatemers

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28
Q

Bacteriophage Mu

A
  • “mutator” phage
  • useful in bacterial genetics
  • temperate phage
  • replicates by transposition
  • large virus with an icosahedral head, helical tail, and six tail fibers
  • invertible G region of genome determines host range
  • genome is integrated into the host
    chromosome via a transposase
  • in both lytic and lysogenic pathways, the genome is replicated as part of a large DNA molecule
  • genome is packaged into the virion with short (5 bp) sequences of host DNA at either strand
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29
Q

“Mutator” phage

A

Induces mutations in host genome

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30
Q

Bacteriophage Mu replicates by ___.

A

Transposition

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31
Q

Bacteriophage Mu

Genome is integrated into the host chromosome via a ___.

A

Transposase

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32
Q

Bacteriophage Mu

Invertible G region of genome determines ___ ___.

A

Host range

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33
Q

Bacteriophage Mu

Lysogenic state requires sufficient amounts of a repressor protein to prevent transcription of ___ ___ ____.

A

Integrated Mu DNA

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34
Q

T4

A

Nucleic acid: dsDNA, linear
Structure: Icosahedral
Replication: concatemers; circular permutation; terminal repeats that are not identical

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35
Q

Lambda

A

Nucleic acid: dsDNA, linear
Structure: head & tail
Replication: rolling circle replication; temperate phage

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36
Q

Phi X174

A

Nucleic acid: ssDNA, circular
Structure: icosahedral
Replication: makes a replicative form; rolling circle replication

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37
Q

M13

A

Nucleic acid: ssDNA, circular
Structure: filamentous, helical
Replication: makes a replicative form; virions exit without lysis

38
Q

T7

A

Nucleic acid: daDNA, linear
Structure: head & tail
Replication: concatemers, terminal repeats that are identical

39
Q

Mu

A

Nucleic acid: dsDNA, linear
Structure: head & tail
Replication: temperate phage, transposase

40
Q

Double-stranded DNA animal viruses that have unusual replication strategies:

A

Pox viruses

Adenoviruses

41
Q

Pox viruses - class I

A
  • among the most complex and largest animal viruses known
  • DNA replicates in the cytoplasm
  • linear, double-stranded DNA virus
42
Q

Pox viruses - class I

DNA replicates in the ___.

43
Q

Adenoviruses - class I

A
  • major group of icosahedral, linear, double-stranded DNA viruses
  • cause mild respiratory infections in humans
  • DNA replicates in the nucleus
44
Q

Adenoviruses - class I

DNA replicates in the ___.

45
Q

Replication requires protein primers and avoids synthesis of a ___ ___.

A

Lagging strand

46
Q

Some DNA animal viruses can induce cancer:

A

Polyomavirus SV40

Herpesviruses

47
Q

Polyomavirus SV40 - class I

A
  • induces tumors in animals
  • noneveloped virion with an icosahedral head
  • no enzymes in the virion; replicates in the host nucleus
  • DNA is circular
  • small genome, has overlapping genes
48
Q

Polyomavirus SV40 - class I

Replicates in host ___.

49
Q

In permissive host cells,…

A

Virus infection results in the formation of new virions and the lysis of the host cell

50
Q

In nonpermissive host cells,…

A

The virus DNA becomes integrated into host DNA, genetically altering cells in the process

51
Q

Herpesvirus - class I

A
  • large group of viruses that cause diseases in humans and animals
  • able to remain latent for extended periods of time
  • an important group causes clinical forms of cancer
  • infection follows attachment of virions to specific cell receptors
  • three classes of mRNA are produced
52
Q

Herpesvirus

Three classes of mRNA are produced:

A

Immediate early
Delayed early
Late

53
Q

Immediate early

A

Encodes five regulatory proteins

54
Q

Delayed early

A

Encodes DNA replication proteins

55
Q

Late

A

Encodes structural proteins of the virus particle

56
Q

Herpesvirus

An important group causes clinical forms of cancer:

A
  • Epstein-Barr virus (mononucleosis)

- Burkitt’s lymphoma (cancer of the lymphatic system)

57
Q

Poliovirus - class IV

A
  • small virus
  • host RNA and protein synthesis are inhibited when poliovirus replication begins
  • paralytic vs. nonparalytic polio
58
Q

In ___ viral RNA is translated directly, producing a single long, giant protein that undergoes self-cleavage to generate about 20 smaller proteins necessary for nucleic acid replication and virus assembly.

A

Poliovirus

59
Q

Polyprotein

A

A single long, giant protein

60
Q

___ polio can affect the spinal cord, the brain stem, or both.

61
Q

FDR was paralyzed from the waist down due to what virus?

A

Poliovirus

62
Q

Coronavirus - class IV

A
  • larger virus

- cause respiratory infections, including SARS, in humans and animals

63
Q

SARS

A

Severe acute respiratory syndrome

64
Q

Coronavirus virions

A
  • are enveloped

- contain club-shaped glycoprotein spikes on their surfaces

65
Q

Negative-strand RNAs are complementary to the ___.

66
Q

Negative-strand RNA viruses

Only those that infect ___ are known.

67
Q

Rhabdovirus - class V

Include viruses that cause:

A
  • rabies in animals and humans

- vesicular stomatitis in cattle, pigs, and horses

68
Q

Rhabdovirus - class V

A
  • enveloped viruses

- virion is bullet-shaped

69
Q

RNA of rhabdoviruses is transcribed in the host cytoplasm into two distinct classes:

A
  1. Series of mRNAs encoding the structural genes of the virus
  2. Positive-strand RNA that is a copy of the complete viral genome
70
Q

Influenza - class V

A
  • enveloped, pleomorphic virus
  • segmented genome
  • surface proteins interact with host cell surface
71
Q

___ causes clumping of red blood cells.

A

Hemagglutinin

72
Q

___ breaks down sialic acid component of host cytoplasmic membrane.

A

Neuraminidase

73
Q

Processes that help influenza elude the host immune system:

A
  • antigenic shift

- antigenic drift

74
Q

Antigenic shift

A
  • portions of the RNA genome from two genetically distinct strains of virus infecting the same cell are reassorted
  • generates virions that express a unique set of surface proteins
75
Q

Antigenic drift

A

Structure of neuraminidase and hemagglutinin proteins are subtly altered

76
Q

Reoviruses - class III

A
  • nonenveloped nucleocapsid with a double shell of icosahedral symmetry
  • virions contain virus-encoded enzymes necessary to synthesize mRNA and the new RNA genomes
  • genome segmented into 10-12 molecules of linear double-stranded RNA
  • replication occurs exclusively in host cytoplasm within the nucleocapsid
77
Q

___ (RNA viruses) and ___ (DNA viruses) use reverse transcriptase for replication.

A

Retroviruses; hepadnaviruses

78
Q

Retroviruses - class VI

A
  • enveloped virions that contain two copies of the RNA genome
  • virion contains several enzymes
  • gene expression and protein processing are complex
79
Q

Retroviruses

Virion contains several enzymes

Includes ___ ___ used to make DNA copy of genome.

A

Reverse transcriptase

80
Q

All retroviruses have the three genes:

81
Q

___ encodes several small viral structural proteins.

82
Q

___ is translated into a large polyprotein.

83
Q

The ___ product is processed into two distinct envelope proteins.

84
Q

Hepadnaviruses - class VII

A
  • virions small, irregular-shapes particles
  • include hepatitis B
  • viral replication occurs through an RNA intermediate
  • unusual genomes (tiny)
85
Q

Viroids -

A

Infectious RNA molecules that lack a protein coat

86
Q

What are infectious RNA molecules that lack a protein coat?

87
Q

Viroids:

A
  • smallest known pathogens
  • cause a number of important plant diseases
  • small, circular, ssRNA molecules
  • do not encode proteins; completely dependent on host-encodes enzymes
88
Q

What are the smallest known pathogens?

89
Q

Prions -

A

Infectious proteins whose extracellular form contains no nucleic acid

90
Q

What are infectious proteins whose extracellular form contains no nucleic acid?

91
Q

Prions:

A
  • known to cause disease in animals
  • host cell contains gene (PrnP) that encodes native form of prion protein that is found in healthy animals
  • prion misfolding results in neurological symptoms of disease
92
Q

Gene that encodes native form of prion protein that is found in healthy animals

Microbiology (26 decks)

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