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28 Cards in this Set
- Front
- Back
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Virus
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Small, obligate intracellular parasite
Genome: DNA/RNA that directs host assembly of new virions |
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Viral Classification/Nomenclature
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Historically based on disease symptoms
Now, based on physiochemical properties |
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Viral Classification
(useful properties) |
Nucleic Acid
Structure: capsid size, shape, (+)/(-) envelope |
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Capsid
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Viral protein coat
Composed of repeating proteins or capsomeres |
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Capsomere
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Aggregate of structural units that comprise viral capsids
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Nucleocapsid
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Viral nucleic acid + capsid
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Enveloped Viruses
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Nucleocapsid + cell membrane (derived from host)
Membrane includes viral surface glycoproteins |
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Naked vs. enveloped viruses
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Enveloped viruses tend to be less stable
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Envelope Glycoproteins
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Encoded by virus
Inserted into membrane prior to budding |
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Virion
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The complete virus particle
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Structural pattern of viruses
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Cubic (icosohedral - 20 sides), helical or complex capsid
May/may not be enveloped |
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"SPARE the coat"
(Functions of viral coat protein) |
Structure/support
Protection Antigenicity Receptor-binding (attachment to host cell) Enzymatic activity |
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What structural component determines viral antigenicity?
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The coat protein
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DNA viruses
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DNA = mRNA template and self-replication
Majority are dsDNA If ssDNA, virus first synthesizes 2nd strand to make dsDNA |
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RNA viruses
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May be ss/dsRNA
Can have single/multiple segments Single segment can be (+)/(-) If (+), serves as mRNA If (-), must create (+) |
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Viral Genome Mutation
(point mutation) |
Important mechanism of mutation in RNA VIRUSES
Why? The RNA polymerase is inherently clumsy and makes many mistakes Majority of mistakes are deleterious but occasionally may result in an advantageous mutation |
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Viral Genome Mutation
(recombination) |
Between RNA molecultes
Homologous: between long, like strands often during synthesis of (+) RNA Non-homologous |
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Viral Genome Mutation
(reassortment) |
Exchange of viral segments
(obviously only works in viruses w/segmented genomes and coinfection of same host cell) |
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Method of Viral Classification
(general) |
Family, Genera, Type, Strain
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Viral Classification Parameters (Family)
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Biochemical/physical parameters
NA type and replication strategry |
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Viral Classification Parameters (Genera)
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Physical/chemical proteins
Shared antigenicity |
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Viral Classification Parameters (Type)
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Serology
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Viral Classification Parameters (Strain)
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The "event" surrounding infecotion (i.e. when, where, etc)
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". . . virales"
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Denotes ORDER
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". . . viridae"
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Denotes FAMILY
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". . . virinae"
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Denotes SUBFAMILY
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". . . virus"
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Denotes GENERA
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Emerging Viruses
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Either newly appeared in population or is expanding its host range (corresponding increase in detectable disease)
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