Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
18 Cards in this Set
- Front
- Back
|
Characterization of Viruses
|
Small nucleoprotein particles with a capability to infect a host cell and then grow within it. they exert high specificity to type of host.
They are non-cellular and cannot reproduce outside of a host cell= intracellular parasite |
|
|
Basic structure of the Virion
|
Nucleic acid (genophore)
Capsid |
|
|
Capsid
|
A protein container in which viral nucleic acid is enclosed
|
|
|
structure of capsid
|
Made up from Capsomers, mostly identical and are made of on or several proteins. A capsid is a quantanary structure of capsomers
|
|
|
Morphology of capsid
|
Regular polyhedron: spherical
Helical cylinder; rod-shaped Specific shape of bacteriophages; Head, tail with filament |
|
|
mutations of viral genom
|
Occur in high frequency, mostly cause there is no repair mechanism.
Attenuated virus: mutated with with UNchanged antigenic properties but with REDUCED pathogenicity (vaccines) |
|
|
recombination of viral genome
|
occur when a cell is simultaneously infected by two similar viruses
High frequency in viruses with fragmented genome |
|
|
Size of viral genome
Size of viral nucleic acid Size of virions |
3-150 genes
3000 - 300 000 nucleotides 20-400nm |
|
|
Outer envelope
|
only some viruses. Outer envelope is derived from plasma membrane of host cell. PROTEINS of the envelope is viral though i.e. they are coded by viral genes, these participate in specific interaction with the host cell
|
|
|
Reproduction of viruses
|
1) Virus is multiplied within the host cell and virions are released from the cell. This is OFTEN accompanied with cell disintegration = Reproductive (lytic) cycle
2) Viral genome is INCORPORATED into the genome of the host cell and thus viral genome is replicated together with the genome od the host cell = Virogeny |
|
|
step one in lytic cycle
|
Adsorption of virion on cell surface and its penetration into the cell
x Fusion of outer envelope with plasma membrane(release of nucleocapsid into host cytoplasm) x receptor mediated endocytosis x bacteriophages inject their nucleic acid into cytoplasm |
|
|
step two in lytic cycle
|
Reproduction of virion within the cell. Virion releases its nucleic acid and host cell further carries out the reproduction.
|
|
|
step three in lytic cycle
|
release of virions from host cell
x lysis of the cell carried out by lytic enzymes of the virus or autolytic processes of the host cell x exocytosis of virions, active process of budding where the outer envelope of the virion is formed |
|
|
Virogeny
|
Viral DNA is replicated within the host cell but virions are not formed and released. Viral DNA is
1) replicated within the host cel independently, functions as a plasmid 2) incorporated into one of the cells chromosomes and replicated together with it |
|
|
Transmission of viruses
|
Horizontal: direct transmission of virus to host cell and then to same generation of host cells
Vertical: transmission from parental generation to offpsring |
|
|
Interaction virus-cell
|
x Death of the cell; degenerative process of the cell or lytic enzymes from the virions
x cytopathic effect; damage of a functional part of the cell => damage of organ, damage may be reversible x without cell damage |
|
|
Animal dsDNA viruses
|
papaovirus (virus SV40 simian virus)
herpesvirus adenovirus poxvirus |
|
|
Animal +ssRNA viruses
|
x Picorna
Polio, Hepatitis A, Rhino x Toga Encephalalitis, rubella |
