Flashcards in MCM 2-1 Virus Structure & Classification Deck (19)
definition of a virus
an organism that encodes a capsid that is an obligate intracellular parasite associated with all life forms
definition of a virion
the particle encoded by a virus genome
consists of a genome, capsid, and optional envelope
how are viruses classified?
by host cell (eukaryotic/ prokaryotic, plant/insect/animal)
by viral genome type (RNA or DNA, single or double stranded)
by virion structure (enveloped or naked, helical/icosahedral, or complex
what is the basic structure of a virus or "the viral genome must have the following three modules"
three basic gene modules
1. capsid proteins - structural because they form the virion. encoding molecule
2. the replicon which encodes nucleic acid polymerase, replication origin, necessary accessory proteins
3. multifactorial proteins that interact with the host. Non-structural because they are left behind in the infected cell and not packed into the virion
unifying principles of virology
All viruses follow a three-part strategy for survival
1. Genome encodes a capsid that protects it outside the cell
2. Genome contains info for infecting a cell, replicating the genome, intracellular survival, and virion assembly
3. Transmission to new host is required to maintain the virus as a species
what led to the discovery of viruses?
diseases led to their discovery, known as "filterable agents"
viruses have a _____ genome
modular. it encodes for the capsid, replicon, and host interacting factors
what happens to virions outside of the host cell
they are inert and lose infectivity over time
virions consist of (3)
a few genes, encased in a protein shell, may or may not be enveloped in a membrane
can be DNA or RNA and can be ss, ds, circular, etc.
protein shell that encapsulates genome
can have helical symmetry due to rolling effect of subunits
or icosahedral symmetry - 20 faces
cluster of proteins outside of the nucleocapsid
proteins that link the core to the envelope
lipid bilayer which can surround the virion
glycosylated proteins found on the outside of envelope
glycoprotein that sticks out, important for attachment and specificity
icosahedral, dsDNA, naked
helical, dsdna, enveloped