Definitions (Ppt I) Flashcards
Progressive hypothesis
Viruses arisen from mobile genetic elements that could move between cells
Regressive or reduction hypothesis
Evolved from free-living ancestors that adapted a parasitic replication strategy
Remnants of cellular organisms
Virus first hypothesis
Viruses predate or coexist with their current host
3 reasons why viruses are beneficial
Biodiversity, residual immunity to subsequent infection, eliminate harmful bacteria
All viruses are obligate _______ organisms
Intracellular
Nucleocapsid parts
Capsid and nucleic acid
(Some have an envelope)
Virus
General description
Virion
Mature infectious particle
Viroid
Plant virus
Are empty capsids infectious?
No
Common viral shapes
Icosahedral, helical, complex symmetry
Which shape is the most common
Icosahedral
Grouping of viruses are based on…
Shape & size of virus, shape & size of nucleic acid, type of nucleic acid, host, vector, location of viral replication, + or - sense, enveloped or non enveloped, capsid symmetry
Families end in
-viridae
Genus end in
-virus
Where are proteins found in viruses
Lipid envelope, capsids, tegument
4 stages of virus cycle
Attachment, penetration, uncoating/replication, release of viral proteins
What are non-specific electrostatic binding molecules & why are they important?
- dextran, heparin sulfate, protoglycans
- assist in attachment stage
What are the specific binding molecules that are used during the attachment stage & their importance
Cell surface receptors determine virus tropism
Binding of FIV to CD4 involves interactions between
Gp120 and CD4
Which viruses don’t require receptors
Viroids
2 methods of penetration for enveloped viruses
Endocytosis (influenza virus) & plasma/endosomal membrane fusion (FIV, reoviruses)
2 methods of penetration for non-enveloped viruses
Pore entry(enteroviruses), lysis of cell endosomal membrane(adenovirus)
