Lecture 3 Flashcards
Common naming system for animal viruses
3
- Diseases that they cause
- Places where virus was first identified
- Other
Common naming system for plant viruses
- Host
- Disease
Properties of viruses that should be the basis for classification
- Disease symptoms
- Host organisms
- Physical structure of the virus particle
Problem with traditional name classification
Too many distinct entities
Committee that classifies viruses into specific orders, families, genus, and species
International Committee on Taxonomy of Viruses
Taxonomy Scheme
Order, Family, Subfamily, Genus, Species
Baltimore Classification System
-System used to categorize viruses based on their genomic structure and the mechanism they use to replicate within a host cell
Hierarchical virus classification system
4 components
- Nature of the nucleic: DNA or RNA
- Symmetry of the capsid
- Presence or absence of an envelope
- Dimensions of the virion and capsid
Family in taxonomy scheme
A group of genera with common characteristics
Species in taxonomy scheme
A cluster of strains that have in common a set pattern of stable properties
Origins of family names
4
- Symptoms of disease caused by viruses
- Sites of infection
- Physical characteristics of the viruses
- Combination
Subfamily in taxonomy scheme
Groups within some large families
Order in Taxonomy Scheme
Group of families with a common characteristic
Genus in taxonomy scheme
A group of virus species sharing common chracteristics
Further breakdowns not recognized by the ICTV
Group, Strain, Varient
Group
Sub-category of species, division often based on genomic sequence similarities or origin
Defective Interfering (DI) Particle
A virus that lacks part of its genome, is unable to replicate by itself and interferes with the replication of a standard virus
Strain
Different lines of isolates of the same virus
Varient
Virus whose phenotype differs from original wild type strain but where the genetic basis for the difference is not known
Common features of satellite viruses and satellite nucleic acids
5
- Does not encodes enzymes required for replication
- Require co-infection with a conventional (Helper) virus
3.Satellite genome is significantly different from the helper virus
4.May affect replication of the helper virus
5.. May increase or decrease severity of disease
Requirement of DI particles
4
- Require helper virus
- Derived from that helper virus
- Product of polymerase “Leaping”
- Interferes with helper virus replication
Viroids
Novel agent of disease in plants. Single circular ssRNA molecule with no protein components
Satellite viruses
2
-Encodes structural proteins that form the viral capsid
-They rely on the helper virus replicative machinery to replicate their genome
Satellite nucleic acids
Similar to satellite viruses except they don’t make their own capsid. They encode only nonstructural proteins or none at all. Rely on a helper virus for replication and capsid formation
How coronaviruses maintain genomic integrity with high error rate of RNA polymerases
Proof-reading 3 to 5 exoribonuclease
