Viral Replication And Taxonomy Flashcards
What does positive RNA mean?
The RNA is just like a mRNA. When a positive stranded RNA virus enters a host cell, its RNA can immediately be translated by the host’s ribosomes into protein.
Mention 4 general characteristics of viruses.
- They are energy-less. They float around until they come in contact with an appropriate cell.
- They are basic life forms composed of a protein coat, called a caspid, that surrounds genetic material.
- The genetic material is either DNA or RNA. Never both.
- Replication of the genetic material occurs when the virus takes control of the host cell’s synthetic machinery.
What is the role of RNA-dependent RNA polymerase?
To transcribe the negative strand of RNA into positive.
What is unique about Reoviridae (including Rotavirus)?
They are the only viruses with a double stranded RNA genome.
What is unique about Parvoviruses?
They have a single stranded DNA genome, whereas most DNA viruses have both a negative (-) and a positive strand.
What are the two types of caspids?
- Icosahedral
2. Helical
What is a capsomer?
Take 1 or more polypeptide chains and organize them into a globular protein subunit. This will be the building block of our structure and is called a capsomer.
What viruses have helical symmetry?
Only RNA viruses. In helical symmetry the protein capsomers are bound to RNA and coiled into a helical nucleoprotein capsid.
Most of the RNA viruses with helical symmetry assume a spherical shape. What is the only exception?
The rhabdoviruses (rabies virus), which have a bullet-shaped capsid.
What are the criteria upon which viruses are classified?
- Nucleic acid
- Capsid
- Envelope
- Size
What is the acronym for the DNA viruses?
HHAPPY
- Herpes
- Hepadna
- Adeno
- Papova
- Parvo
- Pox
What is the rule for most DNA viruses?
Most are double-stranded, show icosahedral symmetry, and replicate in the nucleus (where DNA customarily replicates).
What are the two DNA viruses hat break the rules?
- Parvoviridae - single strand DNA.
2. Poxviridae - Complex, not icosahedral symmetry, and replicates in the cytoplasm.
What are the three DNA viruses that have an envelope?
- Herpes
- Hepadna
- Pox
What are the 3 DNA viruses that do not have an envelop?
- Papova
- Adeno
- Parvo
“A woman must be naked for the PAP smear exam”.
What is the rule for the RNA viruses?
- Single stranded.
- Half are positive stranded, half are negative.
- Show helical capsid symmetry
- Replicate in the cytoplasm.
What are the RNA viruses?
- Toga
- Corona
- Retro
- Reo
- Picorna
- Paramyxo
- Calici
- Flavi
- Orthomyxo
- Bunya
- Arena
- Filo
- Rhabdo
What are the three RNA viruses that are non enveloped?
- Picorna
- Calici
- Reoviridae
What are the five RNA viruses that have icosahedral symmetry?
- Reo
- Picorna
- Toga
- Flavi
- Calici
What are the two RNA viruses that undergo replication in the nucleus?
- Retro
2. Orthomyxo
What is the mnemonic for the (+) stranded RNA viruses?
“The Calcified old emperor Pico is wearing his Crown and Toga and is eating Flavorful grapes from a retro bowl.”
(Calici, Pico, Corona, Toga, Flavi, Retroviridae)
What is the mnemonic for the (-) stranded RNA viruses?
“Old Pete’s Rabid dog Filo fights Paul Bunyon in the Arena”
Orthomyxo, Paramyxo, Rhabdo, Filo, Bunya, and Arena
What are the 4 steps that viruses must complete in order to reproduce?
- Adsorption and penetration.
- Uncoating of the virus.
- Synthesis and assembly of viral products.
- Release of virions from the host cell (either by lysis or budding).
What are the three phases of DNA viral replication?
- Immediate early
- Early
- Late
