Chapter 3.23 Viral Replication and Taxonomy Flashcards by Stephanie Wehbe

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

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What are the different shapes that the nucleic acid strands of a virus?

single-stranded, double-stranded, linear, or looped

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What are the 2 types of RNA viruses?

positive (+) and negative (-)

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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

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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

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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

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What are the 2 special RNA viruses?

Retroviruses- can incorporate into host genome

Reoviridae- only virus with could stranded RNA genome

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What is the enzyme used in retroviruses?

reverse transcriptase

RNA –> DNA

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What strands do DNA viruses have?

negative and positive strand

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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

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What are the 2 types of capsids of viruses?

icosahedral and helical

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What is a capsomer?

building block viral structure

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What is the shape of icosahedral virus?

20 equilateral triangles together

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What genetic material is always involved in the helical shaped viruses?

RNA

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What is the shape of a helical virus?

spherical shape

*except for rhabdoviruses which are bullet shaped

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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?

1. Adsorption and penetration 2. Uncoating of the virus 3. Synthesis and assembly of viral products 4. 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