virus classification Flashcards
what can viruses be classified upon>
genome structure and core
capsid structure
Type of mRNA produced during the replicative cycle of the virus (Baltimore Classification
what is the influenza viruses made up of
RNA polymerase
neuramindidase
hemaggluttin
ion channel
matrix protein
lipid bi layer
nucleo capsid
8 ssRNA strands
what type of virus has a naked helical capsid structure?
TMV
what type of virus has a complex virus capsid structure/
herepsvirus, small pox
what is the Baltimore classification?
System of virus classification
Baltimore classification further detail?
viruses are grouped according to how the mRNA is produced during the replicative cycle of the virus
what are some Viral hosts - Ecological niche
Animal viruses
Plant viruses
Bacteriophages
Zoonoses definion?
are infectious diseases of different species that can be transmitted to humans
E.coli virus?
T4 bacteriophage
Listeria monocytogenes virus?
Caudovirales
The International Committee on Taxonomy of Viruses decide on what>
decide on the classification and nomenclature (naming) of viruses
what are viruses dependant on?
Viruses are dependent on their host’s enzymes and cellular machinery to produce new virions
what happens when the the virus infects a cell?
once infected, the host is forced to replicate viral genetic material
- and translate new proteins, including viral capsomeres and viral enzymes
what are the 6 steps for a virus to infect a cell?
1)attachment
2)penetration
3)uncoating
4)expression-
4)replication -
(assembly)
5)maturation
6)releease
what happens in the attachment/ docking?
The virus first attaches itself to a specific host cell
the T4 phage uses the tail fibres to attach itself to the host cell
The virus attaches to ‘receptors’ - specific proteins, glycoproteins or glycolipids on the host cell
what is direct penetration?
The virus bind to specific receptors(proteins)on the surface of the host cell
This is followed by the injection of genetic material into the host cell
what is membrane fusion?
The virus binds to specific receptors on the host cell
The envelop of the virus then fuses with the host cell membrane
The viral capsid enters the host cell
This is then followed by the ‘uncoating’ of the viral capsid
endocytosis?
The viral envelop binds to specific receptors on the surface of the host cells
The host cell then internalises/engulfs the whole virus
Degradation of the lipid envelop and ‘uncoating’ follows that results in the release of viral genome into the host
what does uncoating involve?
involves the separation of the nucleic acid of the virus from its protein coat
how does uncoating occur?
degradation by host lysozymes - the host lysozymes degrade the capsid protein
- the action of the viral enzyme
how are the new assmenled virons released?
the release of virions is by ‘budding’ resulting in a lipid envelope around the capsid
the release of virion is by membrane rupture (Lysis)
There are two main cycles of viral infection :
The lytic cycle
The lysogenic cycle
summarise the lytic features?
The virus enters the host cell
The genetic material is replicated and transcribed by the host enzymes
The viral components are assembled to form intact virions
The virions leave the cell by lysis
Enveloped viruses leave the cell by the process of budding
Lysogenic Cycle - General Features
The virus enters the host cell
- the viral genetic material is inserted into the genetic material of the host
when the host genome is replicated, the viral genome is
replicated as well
- the virus can live undetected in the host cells for long periods of time
- it can enter the lytic cycle upon activation and result in the formation of numerous virions
how does lysis occur?
After assembly of the new virus particles, an enzyme is produced that breaks down the bacteriacell wall
allows fluid to enter
the cell is eventually filled with viruses which results in lysis of the cell
The new viruses are free to infect other cells and start the process again
what are virulent viruses?
Viruses that reproduce via the lytic cycle are called virulent viruses
how can lysogenic viruses enter the lytic cycle?
when initiated by UV light or certain chemicals
Examples of Lytic viruses
Influenza, Rabies, Tobacco mosaic virus, SARS
Examples of Lysogenic viruses
- Herpes I and II,HIV, Hepatitis B, Varicella-Zoster
