Notes from november 23

RNA virus (Not retrovirus)
• RNA copied by RNA replicase enzyme made by virus copies RNA RNA
• RNA genome translated by host cell rRNA, tRNA and amino acids
e) Assembly of new virions:
- When viral genes have been expressed (i.e. proteins coded for by genes have been made), viral particles spontaneously form (Capsomeres aggregate around viral genetic material, glycoproteins collect on capsomeres)
f) Release of new virions from host cell
i. Lysis of host cell – released viral particles because host cell is destroyed (cell destroyed, this frees viral particles to infect new cells) (EX. E. coli and T4)
ii. Budding from host cell: Virion uses glycoproteins to grab onto host cell membrane, wrap self in membrane and yank itself away – most common way of releasing virions from eukaryotic host cells
V. Consequences of viral infection on host cell
a) Death of cell
- Cell directly lysed by virus
- Cell dies not directly because of virus
i. Ex. Our immune system kills cell because virally – infected
ii. Viral Replication taxes cell function seriously enough that cell dies
b) Disruption of cell function
i. Cell alive, but unable to do much more than make virions
c) “Transformation” (the change of the genetic function of a cells, changing a cell from having one set of genetic characteristics to having another set of characteristics, change in genetic characteristics of cell) of normal cell into cancerous cell —- why? Gives virus more cells to infect because hard to transfer
i. Ex. HPV 16 and 18  infect epithelial cells  integrate own DNA in to host cell’s DNA (DNA genome of HPV integrated into host cell DNA) and knocks out apoptosis (prevents from committing suicide on schedule like a good cell does) in infected cells  Makes the infected host cell into a cancer cell
VI. Viral culture
a) Animals or animal cells/cell culture –
- Must grow viruses in appropriate host cell
b) “Immortalized” human cells: Henrieta Lacks and HelA cells – died of cervical cancer an dcells from her are now used in labs all over the world.