Chapter 5 Flashcards
Why have viruses been termed parasites?
Because viruses must depend on, and take over, the host cell for the majority of their metabolic and biosynthetic reactions
Define susceptiible in the context of virus-cell interactions.
The cell is sensitive to infection by a particular virus, Largely a function of the presence or absence of receptors. Does not necessarily imply productive infection.
Define permissive in the context of virus-cell interactions.
Cell is able to support complete replication of a particular virus. This is a function of the internal biochemistry of the cell, not the presence or absence of receptors.
Define productive in the context of virus-cell interactions.
An infection of a cell by a virus that results in the production of progeny virions.
Define cytocidal in the context of virus-cell interactions.
Virus replication results in damage to cell, resulting in death of the cell
Define persistent in the context of virus-cell interactions.
virus infection that lasts a long time - infection is lasting beyond the time when the immune system might be reasonably expected to clear the infection
Define latent.
Virus infection in which viral genome is maintained, but few viral gene products are made and no virus is produced.
Define inclusion bodies.
They may be viral components or the result of virus-induced degenerative changes - their occurance in tissues demonstrates the presence of a virus infection.
What can inclusion bodies be (morphology/location)?
They may be intranuclear or intracytoplasmic, single or multiple, large or small, acidophilic or basophilic
What is a lytic infection?
alteration in the cell leading to cell death
What is a non-lytic infection?
When there is a persistent infection wherein virus production coexists within the cell without dramatically altering it - when there is little or no visible cell alteration in cell, little metabolic damage, cell division continues, and there may be loss of specialized functions
Define oncogene.
cellular or viral gene whose products are able to transform eukaryotic cells so that they begin to grow like tumor cells
What is a proto-oncogene?
A gene that is normally switched off gets switched on under influence by the virus; it gives rise to v-onc in a transforming virus
Define transduction.
transfer by a virus of cellular genes from one organism or cell to another
Explain the basis for the transforming ability to Rous sarcoma virus.
It is a strongly transforming retrovirus because an oncogene is inserted but does not replace the viral genes, so the virus is still capable of replicating with the addition of the oncogene
Usually when an oncogene is added some of the virus’ genes are replaced and it can no longer replicate. It is not the case here
