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Microimm 2500 > (V) 22: Viral Genomes > Flashcards

(V) 22: Viral Genomes Flashcards

1
Q

Green Fluorescent Protein

A

Physical measurement

  • a gene that will be translated into a fluorescent protein will be inserted into the viral genome
  • then viral protein has a fluorescent tag
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2
Q

Hershey-Chase Experiment

A

proof that the genome is key
- what specifies the production of virus? nucleic acid or protein (shell)

viruses were grown in sulfur labeled protein capsule OR phosphorus labeled DNA core

  1. bacteriophage infects with radioactive precursors to DNA or protein - virus infects bacteria
  2. Blend - virus/phage is removed from cell and leaves genome
  3. Separate - cells and phages are separated by centrifugation
    - get pellet (sediment/heavy) and supernatant (liquid)
  4. Radioactive phosphorus is detected in next gen of bacteriophage
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3
Q

Results of Hershey-Chase Experiment

A

Sulfur was detected in supernatant - protein shell was radioactive
- NOT in cell

Phosphorus was detected IN the cell - pellet part

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4
Q

Modern-day Hershey-Chase experiment

A
  1. bacteriophage mixed w/ cyanine dye binds viral genomes
  2. upon infection into bacterial host, dye leaves bacteriophage and enters host interior

As phage fluorescence drops, cell’s interior fluorescence increases
- more fluorescence in nucleic acid/genome

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5
Q

Baltimore Classification Scheme

A

Nobel for work on Rev. Transcriptase
Found SEVEN groups that differ based on genome

KEY concept: viral genomes must make mRNA. The mRNA must be read by host ribosomes. mRNA is read in the 5’ to 3’ direction

Groups
+ssRNA, -ssRNA, dsRNA, dsDNA, ssRNA w/ DNA intermediate, ssDNA, gapped dsDNA (ss/dsDNA)

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6
Q

Changing btwn groups of Baltimore Classification Scheme

A

dsRNA and -ssRNA become +ssRNA via viral RNA-dependent RNA Poly

dsDNA can become +ssRNA via DNA-dependent RNA-Poly

ss/dsDNA can become dsDNA via DNA Poly or R.T. (same for ssDNA to ss/dsDNA)

+ssRNA w/ DNA intermediate can become ssDNA via viral RNA-dependent DNA Poly (R.T)

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7
Q

Common goal of genes

A

production of ss mRNA to be translated by host cell machinery

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8
Q

mRNA

A

+ strand that is ready to be translated

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9
Q

+DNA strand

A

equivalent polarity to +RNA strand

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10
Q

RNA or DNA complements of + strands

A

considered - strands

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11
Q

7 Types of genomes

A

genomes are DNA or RNA (NOT both)

RNA
ss + RNA
ss - RNA
ds RNA
ss + RNA w/ DNA intermediate

DNA
ss DNA
ds DNA
gapped ds DNA

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12
Q

dsDNA

A

DNA-dependent RNA Poly transcription makes ssRNA from dsDNA

DNA-dependent RNA Poly can be from HOST or can be encoded in VIRAL genome

Ex. Polyomaviridae, Poxviridae

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13
Q

Polyomaviridae

A

virus family within dsDNA

small genome = has to use host’s enzymes

JC Virus - most ppl infected have immune system take care of the virus
- BUT immunocompromised patients will get degenerative brain diseases due to JCV

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14
Q

Poxviridae

A

viral family in dsDNA

DNA-dependent RNA Poly is encoded IN VIRAL genome

larger genome = can make their own DNA-dependent RNA Poly

causes variola virus disease (smallpox)

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15
Q

Gapped dsDNA

A

aka ss/dsDNA (not completely complinentary)
- also contains protein and RNA

ss/dsDNA -> dsDNA -> +ssRNA

  • need to make dsDNA molecule first
  • Viral-associated DNA Poly “FILLS IN gaps” then host DNA-dependent RNA Poly transcription happens to make +ssRNA

Ex. Hepadnaviruses (Hep B viruses)

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16
Q

Hepadnaviruses

A

viral family in gapped dsDNA (ss/dsDNA)

causes Hep B

  • now treatable but can cause liver damage
  • 100x more infectious than HIV-1 = more infectious particles per normal particles
17
Q

Does HIV or Hep B have a higher Particle/PFU ratio?

A

HIV because it is less infectious, meaning it has less infectious particles and a higher ratio

18
Q

ssDNA genomes

A

ss DNA -> ss/dsDNA -> dsDNA -> + ssRNA

  • single strands CANNOT be copied to mRNA
  • host DNA Poly makes dsDNA
  • host RNA Poly makes mRNA (+ssRNA)

Ex. Paroviridae

19
Q

Paroviridae

A

viral family within ssDNA

causes paroviruses
- mostly known for cat/dog infections
- infect cells of intestine, hematopoietic system and fetus
- Ex. canine paroviruses infect and kill puppies

20
Q

Viral RNA genomes

A
  • host does NOT have an RNA-dependent RNA Poly
  • so -RNA strand needs a virally encoded RNA-dependent RNA Poly to make mRNA readable by host translation machinery
21
Q

dsRNA

A
  • dsRNA CANNOT be translated
  • make +RNA strand using viral RNA-dependent RNA Poly and -RNA strand as a template
  • the new +RNA strand becomes mRNA

Ex. Reoviridae

22
Q

Reoviridae

A

viral family within dsRNA

Virus: Rotavirus (not effective vaccine)

  • 4/5 children in their 1st 5 yeas of live develop rotavirus
  • most important cause of gastroenteritis worldwide and infant mortality in developing world
  • dehydration is main contributor to mortality
  • fever, diarrhea, ab pain
23
Q

ss+ RNA

A

READY TO GO

No need for virally encoded RNA-dependent Poly

Ex. Picornaviridae, Coronoviridae

24
Q

Picornaviridae

A

viral family within ss+RNA

causes poliovirus

  • causes paralytic poliomyelitis
  • disabling paralysis
  • inflammation of motor neurons of spinal cord and brain stem
25
Q

Coronaviridae

A

viral family within ss +RNA

causes SARS- CoV2

26
Q

ss+RNA with DNA intermediate

A

“ready to go” BUT they have Reverse Transcriptase that allows insertion into our genome for the rest of our lives

  • Rev. Transcriptase takes +RNA to make ssDNA then dsDNA and back to +sssRNA (RT makes DNA from RNA)
  • remember ssDNA cannot be transcribed –> cellular DNA Poly makes dsDNA and that is transcribed to mRNA

Ex. Retroviridae

27
Q

Retroviridae

A

viral family in ss+RNA w/ DNA intermediate

Ex. HIV

28
Q

ss (-) RNA

A

(-) RNA needs to be copied by viral RNA-dependent RNA Poly to +ssRNA
- NOT a host enzyme

Ex. Paramyxoviridae, Orthomyxoviridae, Filoviridae
- myxo = mucus

29
Q

Paramyxoviridae

A

viral family in ss (-) RNA

causes measles

30
Q

Orthomyxoviridae

A

viral family in ss (-) RNA

Ex. influenza virus, respiratory disease

31
Q

Filoviridae

A

viral family in ss (-) RNA

ex. Ebola virus

  • need to make +mRNA
  • need viral RNA-dep RNA Poly (L protein)

Microimm 2500 (29 decks)

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