Virus Structure and Classification Flashcards
1
Q
Background and Significance of viruses
A
- all forms of life have viruses
- viruses and their hosts have co-evolved
- viral diseases have altered our history, ie AIDS, smallpox, influenza
- many of the concepts and tools of molecular biology have been derived from the study of viruses and their host cells
- > 4,000 viruses identified
2
Q
Viruses as Filterable Agents
A
- homogenize the tissue
- then concentrate it through a filter- 220nm
- bacteria were trapped by the filter (filter becomes infection), viruses were not (filtrate remains infectious)
3
Q
Virus size
A
- virsuses too small to be seen with light microscopes
- they are about 10^-7 - 10^-8
- requires tissue growth
4
Q
Properties of viruses
A
- viruses are associated with all life forms
- viruses are obligate intracellular parasites
- definition of a virus: A capsid-encoding organism
- capsid: protein shell that encapsulates the nucleic acid genome
- virion: the particle encoded by a virus genome
5
Q
Virus genomes are modular
A
- all viruses have 3 basic gene modules
1) capsid proteins
2) the replicon
3) Host interacting factors - multifunctional proteins that interact with the host, usually non structural because they are left behind in the infected cell and not packaged into the virion
6
Q
Virus Structure
A
- helical or Icosahedral or complex symmetry capsid
- the capsid shape and genome type are independent
- enveloped virions obtain a lipid bilayer from the host cell
- naked virions lack an envelope
7
Q
Virus Classification
A
Host Cell (Kingdom)
- Eukaryotic or Prokaryotic
- Plant, insect, animal
Genome Type:
- RNA or DNA
- Single or double stranded
Virion Structure
- enveloped or naked
- helical, isosahedral or complex
8
Q
Virion Componenets
A
-Genome segments
-Nucleocapsid- protein that coats genome
-capsid or core
-tegument- the proteins around the capsid layer
-matrix
-envelope
-glycoprotein
spike or fiber
9
Q
Virus survival strategy
A
1- the genome encodes a capsid that protects it outside the cell
2- the genome contains information for infecting a cell, replicating the genome, intracellular survival, and assembling virions
3- transmission to a new host is required to maintain the virus as a species
10
Q
Adenovirus
A
- viral dsDNA
- icosahedral
- naked virus
- has fibers around outside
- Core proteins V, VII, and u, proteins VI and IX, protease, terminal protein
11
Q
Poxvirus
A
- brick shaped
- enveloped
- outer and inner membrane
- dsDNA
12
Q
Influenza virus
A
- enveloped
- helical
- segmented RNA
- HA and NA
- RNA polymerase
13
Q
Retrovirus
A
- integrase, protease, reverse transcriptase
- gp120, gp41
- capsid shape changes from immature to mature
- enveloped
- dsRNA
14
Q
Herpesvirus
A
- enveloped
- envelop proteins
- tegument- lots
- dsDNA
- isosahedral
