Flashcards in Viral Replication And Taxonomy Deck (27):
Mention 4 general characteristics of viruses.
1. They are energy-less. They float around until they come in contact with an appropriate cell.
2. They are basic life forms composed of a protein coat, called a caspid, that surrounds genetic material.
3. The genetic material is either DNA or RNA. Never both.
4. Replication of the genetic material occurs when the virus takes control of the host cell's synthetic machinery.
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.
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?
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?
1. Nucleic acid
What is the acronym for the DNA viruses?
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?
1. 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?
What are the 3 DNA viruses that do not have an envelop?
"A woman must be naked for the PAP smear exam".
What is the rule for the RNA viruses?
1. Single stranded.
2. Half are positive stranded, half are negative.
3. Show helical capsid symmetry
4. Replicate in the cytoplasm.
What are the RNA viruses?
What are the three RNA viruses that are non enveloped?
What are the five RNA viruses that have icosahedral symmetry?
What are the two RNA viruses that undergo replication in the nucleus?
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?
1. Adsorption and penetration.
2. Uncoating of the virus.
3. Synthesis and assembly of viral products.
4. Release of virions from the host cell (either by lysis or budding).
What are the three phases of DNA viral replication?
1. Immediate early
What happens during the immediate early and early phases of the DNA viral replication?
The initially transcribed mRNA here encodes enzymes and proteins needed for DNA replication and for further transcription of late mRNA.
What happens during the late phase of DNA virus replication?
The mRNA is usually transcribed after viral DNA replication has begun and is transcribed from progeny DNA. The capsid structural proteins are synthesized from the late mRNA genome.