november 23 class notes

November 23, 2009- notes
RNA virus (not retrovirus)
• RNA replicase: enzyme made by virus, copies RNA which result in more RNA
• RNA genome translated by host cell rRNA, tRNA, amino acids
a) Assembly of new virions: when viral genes have been expressed ( example: proteins coded for by genes have been made), viral particles spontaneously form. ( capsomeres aggregate around viral genetic material, glycoproteins collect on capsomeres)
b) Release of new virions from host cell
• Lysis of host cell: cell destroyed, this frees viral particles to infect new cells (example: T4phages and E. coli)
• 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
1) Consaequences of viral infection on host cell
a) Death of cell:
• Cell directly lysed by virus
• Cell dies not directly because of virus
 example: our immune system kills cell because virally- infected
 Viral replication taxes all function enough, that all dies
b) Disruption of cell function:
• Cell alive, but unable to do much more than make virions
c) “transformation” of normal cell into cancerous cell:
• Transformation: change in genetic characteristics of a cell
• Example: HPV 16 and 18 infect epithelial cells
 DNA genome of HPV integrates into host cell DNA
 Knocks out apoptosis in infected cells
 Makes cell cancerous
2) Viral culture
a) Animal cells/ cell culture
• Must grow viruses in appropriate host cell
b) “immortalized” human cells: Henrietta Lacks and HeLa cells