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Microbio Midterm II > Lecture 12: Taxonomy of Viruses > Flashcards

Lecture 12: Taxonomy of Viruses Flashcards

1
Q

How are viruses classified?

A

Based on characteristics

Ie Nature of host, type of disease caused, life cycle, type of nucleic acid and strandedness

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2
Q

What is the baltimore classification scheme?

A

Classification based on type of genome

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3
Q

What are class I viruses?

A

dsDNA (lambda, T4, herpes, pox)

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4
Q

What are class II viruses?

A

ssDNA (phiX174)

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5
Q

What are class III viruses?

A

dsRNA

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6
Q

What are class IV viruses?

A

ssRNA (+)

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7
Q

What are class V viruses?

A

ssRNA (-)

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8
Q

What are class VI viruses?

A

ssRNA (Replicates with DNA intermediate)

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9
Q

What are class VII viruses?

A

dsDNA (replicated with RNA intermediate)

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10
Q

What does + configuration mean? (RNA)

A

Same strand as mRNA, translated directly

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11
Q

What does - configuration mean? (RNA)

A

Complementary to mRNA, needs to be transcribed into + strand before translation

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12
Q

What are the 5 steps of the viral life cycle?

A
  1. Attachment
  2. Penetration
  3. Replication of nucleic acid, transcription and protein synthesis
  4. Maturation
  5. Release
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13
Q

What occurs in the penetration stage of the viral life cycle?

A

Virus genome enters cell
Naked viruses: complete virion may enter cell
Enveloped viruses: may leave envelope @ cell surface, only nucleocapsid enters cell, or whole virus enters cell

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14
Q

What occurs in the maturation stage of the viral life cycle?

A

Assembly of virus components.

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15
Q

What is the latent period in the viral life cycle?

A

Replicating, making new proteins (eclipse)

Maturation-time needed for component assembly

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16
Q

What is the rise period of the viral life cycle?

A

Virions detected outside of cell, lysis

can also bud out if virus is enveloped

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17
Q

What is viropexis?

A

process whereby certain viruses become attached to a cell wall and are incorporated into the cell by endocytosis

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18
Q

What is burst size?

A

of virions released through lysis

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19
Q

What are the 2 types of bacteriophages?

A

Virulent and temperate

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20
Q

How does T4 infect bacteria?

A
  1. T4 attaches to core region of LPS by tail fibres
  2. Tail sheath contracts, forces central core through outer membrane
  3. Tail lysozymes digest peptidoglycan
  4. DNA enters cytoplasm
21
Q

How does T4 replicate?

A

Nucleases and DNA pol and new sigma factors=new phage DNA

Self assembly=mature phage

22
Q

What kind of phage is lambda?

A

Temperate phage

23
Q

What kind of phage is lambda?

A

Temperate phage, phage carried on chromosome. Contains linear dsDNA with cohesive ends.

24
Q

What is a prophage?

A

Phage genome within host cell membrane

25
What is a lysogen?
Bacterium that contains prophage
26
What are cohesive ends?
Single stranded dsDNA, allows it to form into circular DNA (complementary bps)
27
Where is the lamdba genome integrated on the bacterial chromosome?
attlambda site. Lambda integrase catalyzes integration of phage genome at this site.
28
What kind of phage is phix174?
+ strand phage , ssDNA
29
How does phix174 replicate?
1. replicative form (- strand formed to make dsDNA) made, replication via rolling cycle 2. replicative form of DNA nicked by Gene A protein 3. New + strand begins synthesis
30
What kind of phage is MS2?
ssRNA, + strand
31
How does MS2 infect bacteria?
Genome is first used as mRNA, directs synthesis of RNA replicase (RNA dependant RNA polymerase:host doesn't have) RNA replicase synthesizes - strand RNA->used to provide additional mRNA and genome
32
Where are the genome of DNA viruses replicated?
Nucleus
33
Where are the genome of RNA viruses replicated?
Cytoplasm
34
What kind of viruses are Herpes and HPV?
DNA viruses
35
How do herpes and HPV infect cells?
Viropexis, nucleocapsid transported to nucleus=viral DNA uncoated Assembly occurs in nucleus, envelope added via budding through inner membrane of nucleus
36
What kind of viruses are polio and hep A?
+ strand ssRNA
37
What kind of viruses are measles, rabies and influenza?
- strand ssRNA
38
What kind of viruses use dsRNA?
Rotavirous (Reovirus)
39
What is a retrovirus?
Virion carries 2 identical copies of genome, reverse transcriptase, integrase, and proteases DNA Genome travels to nucleus and is integrated into host DNA
40
What are LTR's?
Long terminal repeats: Contain promoters for transcription & participate in integration.
41
What is a provirus?
Integrated Viral DNA. cannot be excised from host
42
What does reverse transcriptase do?
Transcribes RNA to DNA
43
Which viruses use RNA dependent RNA polymerase?
dsRNA and -ssRNA
44
What is a heterokaryon?
multinucleate cell that contains genetically different nuclei
45
What is cell fusion?
Two cells are brought together by a virus and fuse.
46
What are the 4 ways a viral infection can turn normal cells into tumor cells?
1. Transduction 2. Insertion of strong promoter 3. Inactivation of tumor supressor gene 4. Expression of a viral protein that induces transformation
47
What is transduction? (RNA virus)
1. Virus take oncogene from host and places oncogene into its own genome 2. Virus places this oncogene into healthy cell=tumor
48
Describe the mechanism of inserting a promotor. (Retrovirus)
(No oncogenes encoded) 1. Insertion of a strong promoter of provirus next to protooncogene 2. oncogene is expressed at high levels

Microbio Midterm II (7 decks)

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