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Biosystems II
Virus Characteristics
29
Biology
Graduate
03/07/2012

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Term
unifying properties of viruses
Definition
-obligate intracellular molecular parasites
-either DNA or RNA surrounded by protein capsid
-virus genome directs synthesis within host cell
-progeny are produced by the assembly of newly made viral components
-progeny spreads infection to new cells
Term
virion function
Definition
-plays an active role in delivering the viral genome to an appropriate host cell to initiate the viral reproductive cycle
-protection
-attachment
-dissassemble at appropriate time
Term
capsomere
Definition
-morphological unit of capsid
Term
capsid
Definition
-protein coat surrounding genome
Term
envelope
Definition
-lipid bilayer surrounding virion
-derived from host cell (same as cell membrane)
-spikes (attachment)
Term
icosahedral
Definition
sphere like
Term
helical
Definition
rod like
Term
RNA viruses
Definition
-almost all ss RNA
-(+) sense - same polarity as mRNA (no transcription needed)
-(-) sense - opposite polarity to mRNA
Term
viral transmission
Definition
-inhaled droplets
-agriculture
-direct transfer/mother to newborn
-insect bite
-changes in environment
-population dynamics
-commerce and trade
Term
viral spread
Definition
-entry replication and tissue tropism occur at same anatomic site
-neural spread
-hematogenous spread
Term
infectious spread
Definition
-attachment/adsorption (glycoproteins)
-entry/uptake
-uncoating (release genetic material)
-synthesis of viral components (transcription,translation,replication)
-assembly
-release
Term
attachment factors
Definition
-influenza-sialic acid
-rabies-Ach receptor
-HIV-CD4
-EBV-CD21
-Semliki Forest Virus-MHC molecules
Term
HIV attachment factors
Definition
-macrophage-CD4 and CCR5
-T-cell-CD4 and CXCR4
Term
virus entry and uncoating
Definition
-fusion with host cell membrane
-receptor mediated endocytosis
-uncoating at the plasma membrane
-clathrin-mediated endoytosis
Term
fusion with host cell membrane
Definition
-fusion
-uncoating
Term
receptor mediated endocytosis
Definition
-forms endosome (host cell membrane)
-acidification, fusion, uncoating
Term
uncoating at the plasma membrane
Definition
-uncoating
-pore formation
Term
clathrin mediated endocytosis
Definition
-endosome (host cell membrane)
-acidification, lysis,uncoating
-docking at nuclear envelope
Term
synthesis of viral components
Definition
-early gene transcripts-encode regulatory proteins (non structural/enzymes in DNA metabolism and replication)
-late gene transcripts-DNA replication precedes transcription of late genes, encode structural proteins (capsomeres, envelope proteins)
Term
viral mRNA production
Definition
-DNA viruses use host RNA polymerase to transcribe
-(+) sense ssRNA functions as mRNA and encodes viral RNA polymerase
-retrovirus-reverese trancriptase (RNA dependent DNA polymerase)
-(-) sense ssRNA - transcribed by virus encoded RNA polymerase
-double stranded RNA virus-(-) sense strand RNA transcribed by virus encoded RNA polymerase
-viral mRNA translated by cellular ribosomes
Term
virus assembly and release
Definition
-association of nucleic acid, capsid proteins, and envelope proteins
-host or viral enzymes aid in viral progeny release from cell
Term
acute (lytic) infection
Definition
-viral replication results in cell death
-commonly in non-enveloped virus
Term
chronic (persistant) infection
Definition
-virus persists and grows at slow rate following acute illness
-infective but symptom-less
Term
latent infection
Definition
-virus remains inactive, low progeny produced
-DNA/RNA exist in host cell (episomal) or integrate into host genome
Term
oncolytic infection
Definition
-viral induction of cancer
-incorporate in host genome and disregulates cell growth
Term
viral evolution
Definition
-rapid replication
-error prone replication
-selective pressures
-antigenic variation
Term
basic necessities for survival
Definition
-genome codes for:
-structure
-replication
-delivery
Term
episomal
Definition
-like plasmids
-nucleic acids of latent viruses
Term
nucleic acid replication primarily takes place in
Definition
nucleus
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