Viruses Flashcards
What are the 2 characteristics of viruses?
- NRG-less and must use a host cell for NRG and machinery.
- Capsid (proteins) that surrounds either DNA ORRRRR RNA (not both). Does not have organelles or ribosomes, but they can have structural proteins or enzymes in capsid
- May be surounded by a lipid bilayer (envelope)
What type of genetic material can viruses have?
does it encode a little or alot of info?
- Either DNA or RNA
- SS, DS, linear, loopsed, etc
either
What are the 2 types of RNA viruses?
What is the process they must go through to make proteins?
+ stranded; acts like mRNA and can be directly translated to protein
- stranded;
RNA- => RNA+ via RNA dependent RNA polymermase (RDRP), which it carries in its capsid
What provides RNA- viruses with RDRP?
They must carry their own bc humans dont have one
What are the 2 special RNA viruses?
- Retrovirus (HIV): can incorporate into the host genome
2. Reoviridae (rotavirus): only viruses with a dsRNA.
Viruses have have DNA genetic information.
What is it like and how does it make proteins?
What is an exception to this?
Most have both dsDNA: one (+) strand and one (-) strand
(-) strand is read, while the (+) strand is ignored.
Parvovirus has a ssDNA
Viruses are have capsids and some have envelopes. What are the 2 types of capsids and what genetic material do they often contain?
- Icosahedral capsids: RNA or DNA
2. Helical: RNA
How are icosahedral and helical capsids made?
What is the exception to the helical capsids?
Take 1 or more polypeptide chain => make it into a capsomer (globular protein that is the building block for )
Icosahedral=> make it into a triangle => place 20 together
Helical: take capsomer and attached RNA => coil it into a helix => spherical
-exception is rhabdoviruses (rabies) have bullet shaped capsid
Rhadoviruses have what shaped capsid?
bullet
Not all viruses have to have a envelope.
Those that do not: NAKED
Those that do: ENVELOPED
How do those that do make them?
Take a peice of hosts nuclear, cytoplasmic membrane, which are studded w glycoproteins ;)
What are our DNA viruses; using the mneuomic?
HHAPPPy
Herpes* Hepadna* Adeno Papova Parvo Pox*
*=enveloped
General characteristisc of DNA viruses
SS/DS?
Shape of capsid?
Where do they replicate?
dsDNA
Icosahedral
nucleus
Most DNA viruses are
dsDNA, icosahedral, and replicate in nucleus. what are the 2 exceptions?
- Parvoviridae is ssDNA (one PAR hole in golf)
2. Poxviridae is shaped like a BOX; not icosahedral
Which DNA viruses are naked (no evnvelope)
Women must be a naked for a PAP smear.
- Parvo
- Adena
- Papova
General characteristisc of RNA viruses
SS/DS?
Shape of capsid?
Where do they replicate?
Enveloped or non?
SS (half are + and half are -)
Helical
Cytoplasm
enveloped
What are the RNA+ viruses?
The CALCIfied old emperor PICORNA is wearing his Crown and
TOGA and eating FLAVorful grapes from a RETRO bowl.
Calici, Pico, Corona, Toga, Flavi, and Retroviridae.
What are the RNA- viruses?
Old Pete’s RABid dog FILO fights paul BUNYon in the ARENA.
Orthomyxo, Paramyxo, Rhabdo, Filo, Bunya, and Arenaviridae
Most RNA viruses are ssRNA, helical, and replicate in cytoplasm. what are the exceptions?
- dsDNA
- non-enveloped
- icosahedral shaped
- replicate in nucleus
- Reoviridae are dsRNA
- 3 are non-eveloped: PCR (picrona, calici and reoviridae)
- 5 are shaped like a icosahedral: Reo, Picorna, Toga, Flavi, Calici, Rhabdo
- 2 replicate in nucleus: retro and orthomyco
What is the only virus with a dsRNA?
Reoviridae (rotovirus)
What are the 3 naked RNA viruses?
PCR
Picrona
Calici
Reoviridae
What are the 5 RNA viruses shaped like icosahedral?
Reo, picorna, togo, flavi, calici, Rhabdo
What 2 RNA virurses replicated in nucleus?
retro and orthomyco
What are the 4 steps of viral replication?
- Adsorption and penetration
- Uncoating the virus
- Synthesis and assembly of the viral proteins while inhibiting the host’s protein
synthesis and assembly. - Release of virons from the host cell (either by lysis or budding).
PRocess of viral replcation
in RNA, retroviruses and DNA
- Adsorption and penetration: The viral particle binds to the host cell membrane, typically at a receptor => completely internalized by endocytosis or fusion of the viral envelope
with the host cell membrane. - Uncoating: The nucleic acid (DNA or RNA) is released from the capsid into the nucleus or
cytoplasm.
2A (Replication of RNA viruses): occurs in cytoplasm:
o Typically do all of their work in the cytoplasm: + strand are ready for translation as soon as they are in the cell => + strand then makes the RDRP so that there are – strands for
replication.
o – strand RNA viruses carry a RDRP with them when they infect a cell so that their
genetic info can be turned into + strand and translated into proteins.
2B Replication of retroviruses:
o They are single strand + RNA viruses, but do not undergo immediate translation
once they invade the cell.
o They carry a preformed RNA dependent DNA polymerase (RDDP) that they use
to convert their RNA => DNA => inserted into the host DNA => converted into mRNA.
2C (DNA replication): 2 phases of transcription: immediate early, early and late
immediate early and early: initially transcribed mRNA codes for enzymes and proteins needed for DNA replication and to transcribe late mRNA
late transcription: mRNA is transcribed after a viral DNA replication begins and is transcribed from progeny DNA=> making capsid proteins
How are DNA viruses assembled and released?
Naked and enveloped release:
- assemble into intact viron and released
- Naked virons can be released via exocytosis or lyse the cell
- Enveloped leave via golgi, NM, CM, while taking peice of membranous coat :)
what is the fate of the host cell?
- death.
- virus leaves oncogenes and allow the cells to grow and proliferate (Transform)
- Latent infection: virus chills and hangs
- Chronic slow infection: not quiet latent infection; v takes YEARS to cause illness
Viruses are _____, ______agents
obligate
intracellular (parasites)
Smallest and largest DNA virus?
Smallest: Parvo (22nm)
Largest: Pox (250)
Smallest and largest RNA virus?
Smallest: Picorna (27nm)
Largest: Retro (120nm); similar in size to smallest bacteria Mycoplasma pneuomiae (150nm)
