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Virology > Hepadnaviridae & Retroviridae > Flashcards

Hepadnaviridae & Retroviridae Flashcards

1
Q

What group are hepadnaviridae in?

A

Group 7–>dsDNA w/ RNA int

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2
Q

True or false: Hepadnaviridae do not need to bring in their own DNA pol

A

False
-Need to bring in VIRAL RNA dep DNA pol (REVERSE TRANSCRIPTASE)

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3
Q

What pathogens are in Hepadnaviridae

A

Hepatitis B

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4
Q

Why is Hepatitis B concerning?

A

-Common–>1/3 of population has gotten it
-90% clear infection, but 1% develop acute liver failure & die
-can develop life long chronic infection (worse in children)
-cirrhosis
-cancer

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5
Q

Differences between Hepatitis A, B, and C

A

Hep A: Picornaviridae–>Group 4 (+)ssRNA, mild infection, vaccine exists
Hep B: Hepadnaviridae, Group 7 dsDNA w/ RNA int, chronic infection, vaccine exists–>not available globally
Hep C: Flaviviridae, Group 4 (+)ssRNA, chronic, no vaccine

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6
Q

True or false: Hepatitis kills less people than malaria, tuberculosis, and HIV/AIDS

A

False
-Hepatitis has killed more in 2013

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7
Q

What family is Hepatitis E in?

A

Togaviridae

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8
Q

Which hepatitis are the biggest killer?

A

Hepatitis B and C

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9
Q

Is Hepadnaviridae enveloped or non, what type of capsid?

A

-Enveloped
-Icosahedral

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10
Q

Hepadnaviridae genome characteristics?

A

-rcDNA (relaxed circular DNA)–>strand is not complete/covalently linked, not circular
-1 DNA strand has viral pol at 5’ end
-Other strand has m7G capped RNA

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11
Q

Hepadnaviridae life cycle

A
  1. Entry–> fusion or endocytosis
  2. Becomes circular dsDNA –>Host DNA pol repairs rcDNA into cccDNA
  3. RNA transcription (host DNA dep RNA pol)–>5 protein coding mRNA, includes pgRNA
  4. Protein translation–> 7 proteins
  5. Encapsidation–>pgRNA is packed into capsids
  6. Genome synthesis–>made by VIRAL reverse transcriptase
  7. Budding and exocytosis
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12
Q

Once in the nucleus hepadnaviridae do what?

A

dsDNA becomes circular by cccDNA (covalently closed circular DNA)

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13
Q

What is an advantage rcDNA becoming cccDNA?

A

Circular genomes are more stable and can stay for decades
-b/c circular/episomal it is not recognized as non-self by host

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14
Q

How is pgRNA made and what does it do?

A

HOST RNA makes 5 RNAs that includes pgRNA
-used as a template for reverse transcriptase

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15
Q

True or false: pgRNAs and reverse transcriptase are packaged into virions after reverse transcriptase steps occur

A

False
-pgRNAs and reverse transcriptase are packaged into virions BEFORE RT steps

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16
Q

Reverse transcription steps for Hepadnaviridae

A
  1. RT binds to stem loop at 5’ end to start
  2. RT switches to identical seq at 3’ end
  3. DNA is made, RNA is degraded, but a little remains
  4. The RNA starts 2nd strand synthesis
  5. 2nd strand uses DNA as template so DNA dep DNA pol is used
  6. dNTPs are used up and synthesis stops making rcDNA (not circular)
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17
Q

True or false: Hepadnaviridae make many infectious particles

A

False
-Icosahedral capsid does not need nucleic acid to from so it forms many non-infectious particles

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18
Q

What are satellite virus and example of one

A

Parasitize the machinery of other viruses
-Hepatitis D

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19
Q

What does Hep D need to be infectious?

A

Requires co-infection with Hep B virus for envelope proteins
-uses structural proteins of Hep B

20
Q

Can Hep B exist w/out Hep D?

A

Yes
-Hep D cannot exist w/out Hep B

21
Q

What group are Retroviridae in?

A

Group 6–>(+)ssRNA w/ DNA intermediate

22
Q

True or false: (+)ssRNA in retroviridae is immediately translated

A

False
-Immediately reverse transcribed–>converted into dsDNA

23
Q

Why do Retroviridae turn (+)ssRNA into dsDNA first?

A

dsDNA is stable

24
Q

What is packaged in virions in Group 6 and what is packaged in group 7?

A

Group 6: RNA
Group 7: DNA

25
Q

Where is reverse transcriptase located in retroviridae?

A

In capsid

26
Q

True or false: Retroviridae is non-enveloped

A

False
-enveloped
-nuclear replication

27
Q

What pathogens are in Retroviridae?

A

-Human immunodeficiency virus (HIV)–>does not cause cancer
-Human T lymphotrophic virus (HTLV)–>causes cancer

28
Q

What 2 states does retroviridae exist in?

A
  1. Extracellular RNA retrovirus
  2. Integrated Provirus
29
Q

What is provirus?

A

Genetic info of virus is integrated into genome of host and can replicate

30
Q

True or false: In retroviridae, once dsDNA integrates it can be excised out

A

False
-stays forever–>cannot be taken out without killing host

31
Q

What is in RNA genome in retroviridae

A
  1. Repeat region R(U5 and U3)–>genome replication
  2. Primer binding site (PBS)–>genome replication
  3. Packaging signal (psi)–>genome packaging
  4. Viral genes (gag,pol, env)–>polyprotein coding genes
32
Q

What is in proviral genome in retroviridae

A

Long terminal repeats (LTR)
-genome replication

33
Q

Retroviridae life cycle

A
  1. Entry: fusion (enveloped)
  2. Reverse transcription
  3. Integration (integrase)
34
Q

Retroviruses need to wait for nuclear envelope of host to break down, what kind if cells can they infect then?

A

Infect actively replicating cells

35
Q

Retroviridae reverse transcription steps

A
  1. RT primes tRNA at 5’ end
  2. RT switches to identical seq at 3’ end
  3. DNA is made, RNA template is degraded, a little remains
  4. RNA makes 2nd strand synthesis
  5. 2nd strand uses DNA as template, so RT is DNA dep DNA pol
36
Q

What is the main difference between Hepadnaviridae and Retroviridae reverse transcription steps

A

Hepdna: uses stem loop to start
Retro: primes tRNA to start

37
Q

What is an HIV drug target?

A

Integrase

38
Q

How do retroviridae make multiple viral RNAs

A

Splicing

39
Q

Where are unspliced RNAs?

A

Nucleus

40
Q

What makes structural proteins in retroviridae

A

Gag

40
Q

Why is pol produced at low levels?

A

Retroviruses read through the stop codon 5% of time to make Pol
-Pol doesn’t have its own start codon

41
Q

What makes non-structural proteins in retroviridae

A

Pol

42
Q

What makes envelope proteins in retroviridae

A

Env

43
Q

What proteins need to come in with retroviridae?

A

-Reverse transcriptase
-Host tRNA
-Integrase
-Protease

44
Q

How does the protease in retroviridae differ frim the protease in Picorna, Flavi, Toga, and Corona?

A

Protease is only active when virus starts budding off

Virology (19 decks)

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