Chapter 3.23 Viral Replication and Taxonomy Flashcards
What are the unique characteristics of viruses?
They are energy-less
Have a protein coat (capsid) have no organelles or ribosomes
Have either RNA or DNA, never both!
Replication happens when virus takes control of host machinery
What are the different shapes that the nucleic acid strands of a virus?
single-stranded, double-stranded, linear, or looped
What are the 2 types of RNA viruses?
positive (+) and negative (-)
What does a positive RNA virus mean?
RNA is just like the messenger RNA (mRNA)
When RNA virus enters host cell, it can immediately be translated
What does a negative RNA virus mean?
RNA virus enters the cell but are not able to begin translation
*first must be transcribed into a positive strand of RNA
How does a negative RNA virus transcribe into a positive RNA virus?
negative RNA viruses carry RNA-dependent RNA polymerase when carries out the transcription to positive strand
*human cells don’t have this polymerase so the virus must carry it
What are the 2 special RNA viruses?
Retroviruses- can incorporate into host genome
Reoviridae- only virus with could stranded RNA genome
What is the enzyme used in retroviruses?
reverse transcriptase
RNA –> DNA
What strands do DNA viruses have?
negative and positive strand
What is the difference between the negative and positive strands of DNA on a DNA virus?
Negative strand is the strand of DNA that is read and the positive strand is ignored
*Parvoviruses are the exception and have a single stranded DNA genome
What are the 2 types of capsids of viruses?
icosahedral and helical
What is a capsomer?
building block viral structure
What is the shape of icosahedral virus?
20 equilateral triangles together
What genetic material is always involved in the helical shaped viruses?
RNA
What is the shape of a helical virus?
spherical shape
*except for rhabdoviruses which are bullet shaped
What is the envelope of a virus made out of?
lipid bilayer membrane which the virus tore off the host
- viruses do not have to have membranes- viruses without membranes = naked
- viruses with membranes = enveloped
How are viruses classified?
Nucleic acid, capsid, envelope, size
What are the components of the nuclei acid classification of viruses?
type of nucleic acid- DNA, RNA double vs single stranded single or segmented pieces of nucleic acid positive or negative stranded RNA complexity of genome
What are the 2 classifications of capsid viruses?
icosahedral or helical
What are the 2 classifications of envelope viruses?
naked or enveloped
What is the classification of shape of viruses?
Diameter of helical capsid viruses
Number of capsomers in icosahedral capsids
What is the mneumonic for DNA viruses?
HHAPPP(y) viruses Herpes Hepadna Adeno Papoca Parvo Pox (y)
What is the most common classification of DNA viruses?
double stranded, icosahedral symmetry, replicate in the nucelus
What 2 viruses are exceptions to the “most common” classification of DNA viruses
Parvoviridae- so simple that it only has a single strand of DNA- “ONE PAR” hole in golf
Poxviridae- extremely complex, has double stranded DNA but is not icosahedral, and replicated in the cytoplasm
What 3 DNA viruses have envelopes?
Herpes Hepadna Pox
What 3 DNA viruses are naked?
PAP
PApova, Adeno, PArvo
*women must get naked for their PAP smear exam
What is the most common classification of RNA viruses?
single-stranded, enveloped, helical symmetry and replicate in the cytoplasm
What are the exceptions to the “most common” classification of RNA viruses?
Reoviridae- double stranded
3 nonevneloped- Picorna, Calici and Reoviridae
5 icosahedral shapes- Reo, Picorna, Toga, Flavi, Calci
2 undergo replication in the nucleus- Retro and Orthomyxo
What is the mneumonic for positive stranded RNA?
the CALCIfied old emperor PICO is wearing his CROWN(corona) and TOGA and is eating FLAVorful grapes from a RETRO bowl
(Calici, Pico, Corona, Toga, Flavi, Retroviridae)
What is the mneumonic for negative stranded RNA?
Old Pete’s RABid dog FLIO fights paul BUNyon in the ARENA
Orthomyxo, Paramyxo, Rhabdo, Filo, Bunya, Arenaviridae
What are the 4 steps of RNA viral reproduction?
- Adsorption and penetration
- Uncoating of the virus
- Synthesis and assembly of viral products
- Release of virions form the host cell
What is the difference between Retroviruses and normal viruses?
retroviruses do not undergo immediate translation, the carry preformed RNA dependent DNA polymerase and are transcribed into the DNA
*directly incorporated into the host DNA
What are the phases of DNA viral replication?
immediate early, early, and late transcription
What is a naked virion?
cell that may lyse and release virions or virions may be released by exocytosis
What is an enveloped virion?
initially naked but then acquired it’s envelope by budding through part of the host cell lipid bilayer as it exits
What are the 4 host cell outcomes from viral infection?
Death- host cell’s own function shuts down resulting in cell death
Transformation- activation or introduce oncogenes causing uncontrollable cell growth
Latent infection- virus stays in “sleeping” state until reactivation
Chronic slow infection- virus that cause disease after many years
