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Microbiology Unit 2 > Virus Genetics > Flashcards

Virus Genetics Flashcards

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Biology 101 flashcards
1
Q

Which virus has the fewest genes? How many?

A

Parvovirus

2 genes

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2
Q

What virus has 3 genes?

A

Retrovirus

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3
Q

What virus has 8 genes?

A

Papilloma

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4
Q

What virus has 10 genes and is double stranded?

A

Adenovirus

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5
Q

What virus has 70-100 genes?

A

Herpesvirus

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6
Q

What virus has the greatest number of genes? How many?

A

Poxvirus

200 genes

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7
Q

How is expression of viral genes induced? How is it not induced?

A
  • induced by txn factors binding to promoter region

- not induced by binding of repressor/inducer to operator

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8
Q

Are viral genes eukaryotic or prokaryotic?

A

eukaryotic

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9
Q

How do viruses have tissue specificity?

A

promoters of viral genes are only recognized by txn factors which are expressed in particular tissues

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10
Q

Describe the simple genome of retroviruses

A

genes are linear
one RNA strand
single promoter

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11
Q

Describe the complex genome of adenoviruses, herpesviruses, and poxviruses

A

genes on both strands of DNA
genes often overlap
each gene has own promoter

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12
Q

What 5 aspects make viral genomes efficient?

A 
No non-coding regions
Overlapping reading frames
Translational frameshifts 
Alternate splicing
Polyproteins
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13
Q

What cleaves polyproteins into individual proteins? In what viruses is this an especially good drug target?

A

viral protease

HIV, Hep C

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14
Q

Which are stable - DNA or RNA viruses?

A

DNA stable

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15
Q

What are 3 reasons why RNA viruses are not stable, and have a lot of mutations?

A

error prone RNA pol
No Pol proofreading
some lack 2nd strand - mutation continues

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16
Q

What kinds of mutations happen frequently in viruses? Which kind happens infrequently?

A
  • Frequent: pt mutations, deletions, integration into host genome, recombination, rearrangement, insertion
  • Infrequent: insertions into viral genome
17
Q

How have mutations allowed the measles vaccine to be created?

A
  • so many mutations the host range changed completely

- then non-human strain used to make human vaccine

18
Q

To what drug have herpes simplex mutants become resistant?

A

Ancyclovir

19
Q

To what class of drug have HIV or Hep C mutants become resistant?

A

protease inhibitors

20
Q

To what drug have influenza mutants become resistant?

A

Amantidine

21
Q

What are 5 common phenomena which happen when 2 viruses infect the same cell? Which happens most?

A

Complementation, Phenotypic Mixing, Recombination, Reassortment, Interference (happens most)

22
Q

What is viral complementation? What is an example?

A

When 2 viruses infect same cell, a gene funtion of 1 virus makes up for a mutated/missing gene of the other
ex. Hep B and Hep D must grow together

23
Q

what is viral phenotypic mixing? What is an example?

A

exchange of capsids

ex. 2 polio virus serotypes infect same cell –> end up with capsids which are a mix of both serotypes

24
Q

Are the capsid changes seen in viral phenotypic mixing passed on to next generation?

A

No

25
Q

What does phenotypic mixing produce?

A

pseudotype - genetic material of one virus in capsid or envelope of another

26
Q

What is viral recombination? What does it produce?

A
  • exchange of genes by crossing over at regions of homology

- hybrid virus

27
Q

What is an example of viral recombination to produce a hybrid virus?

A

Eastern equine encephalitis + Sindbis virus = Western equine encephalitis

28
Q

Which forms of virus interaction (when 2 viruses infect same cell) change the genome to produce new strains? Which do not (next gen reverts)?

A

change genome: recombination, reassortment

don’t change genome: complementation, phenotypic mixing, pseudotyping

29
Q

What is viral interference? How is it accomplished (3 ways)?

A

infection by one virus prevents infection by another

  • block receptors
  • compete for resources
  • produce interferon or other anti-viral agents (stim innate immunity)
30
Q

What kind of disorders are mist likely to be treated by gene therapy?

A

monogenic (one gene)

31
Q

What are examples of monogenic disorders which might be treated by gene therapy?

A 
CF
autoimmune
Hemophilia (successful in dogs)
Liver enzyme-deficiency
Retinal disorders (successful in mice)
32
Q

In what two species has gene therapy been successful? What was treated?

A

dogs - hemophilia

mice - retinal disorder

33
Q

What are the four categories of host range mutant viruses used for gene therapy?

A

retroviruses
adenoviruses
adeno-associated
herpes simplex

34
Q

What are 4 problems seen with gene therapy?

A
  • short duration of expression
  • low efficiency of gene transfer
  • severe inflammation in response to virus
  • insertion of virus into genome –> malignant disease

Microbiology Unit 2 (14 decks)

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