Ch. 3 virology Flashcards
All known viruses can be sorted by:
the structure of their genomes
A universal function of viral genomes is:
to specify proteins
All viral genomes must be copied to mRNA to be read by host ribosomes T/F?
T
Baltimore Classification:
All virus must produce mRNA that can be translated by cellular ribosomes
virus with bigger genomes encode for immune evasion and replication cycle
Genomes may be linear or circular
DS DNA
partially double stranded, filled in to produce duplexes.
This repair process must precede mRNA synthesis because transcription can only be performed on dsDNA
Genome is synthesized by reverse transcriptase, translating DNA from RNA
Gapped DNA ex: hep B
Two strategies for RNA virus replication:
1: Reverse transcriptase converts RNA to DNA
2: Viral coding for RNA dependent- RNA polymerase
Cannot be translated (part of a duplex)
(-) strand first copied into mRNA to produce viral proteins
new mRNAs encapsidated and copied to produce _____
dsRNA Ex: Rotavirus
Most plentiful category of virus on the planet
Can be translated directly into protein by host ribosomes
Genome is replicated in two step process: 1. RNA is copied to (-)RNA
2. - strand is copied into ___ strand genomes
(+) ssRNA Ex: coronavirus
Exception: retroviruses
____ must first be copied to + strand mRNA by viral protein (RNA dependent RNA polymerase)
Virions MUST contain protein for performing this process, since the cell doesn’t contain any.
(-) ssRNA Ex. Rhabdoviradae
Viral genomes can be _____ or _____ structures.
secondary; tertiary
Sequences at the end of viral genomes are essential for replication. They include:
priming structures
priming proteins attached to 5’ end
tRNA
internal ribosome entry site
Viral coding strategies:
polyprotein synthesis
multiple mRNA splicing
suppression of termination
Max and min sizes of viral genomes:
RNA viruses: up to 31 kbases; hep B genome is 3.2 kb;
DNA viruses: herpes DNA 150 kb
Purpose of a viral protein can be analyzed by
mutation of the specific protein code
The holy grail of virology is:
dsDNA copy of viral genome carried on bacterial plasmid
Influenza has ___ segments
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