Virology Flashcards
give 6 types of viruses
filamentous viruses, isometric viruses, enveloped viruses, bacteriophages, archael viruses and viroids
what are the 3 main theories for the origin of viruses
regressive, escape, ancient
describe the regressive theory
viruses descend from free living organisms becoming parasitic and losing some functions
describe the escape theory
viruses originate from genetic material ‘escaping’ from genomes of larger organisms
describe the ancient theory
viruses have their origin in self replicating molecules in pre cellular world
what are the 7 pillars of life and which ones do viruses satisfy
organisation, reproduction, evolution (✅) metabolism, response to stimuli, homeostasis, growth
what are the five stages of virus infection/ replication
attachment, penetration, synthesis of nucleic acid and protein, assembly and packaging, release
describe the attachment stage of HIV
the virus first binds to a low affinity receptor, rolls over cell surface until it binds a high affinity CD4 receptor. then binds with co receptors CCr5/CXCR4 to pull closer to membrane and fuse
how do enveloped animal viruses enter
fusion
how do non enveloped animal viruses enter
endocytosis (clathrin mediated)
how do viruses enter plant cells
via a vector (animal feeding eg) or via a damaged cell wall
what are the 4 ways virus synthesis occurs
DNA viruses - host cell machinery
RNA viruses - need to synthesise RNA dependent RNA polymerase
Retroviruses - reverse transcriptase uses host ds dna as template
others - switch between at different points in the lifecycle
give two versions of release of viral particles from cell
lytic and budding
what feature determines which life cycle the viruses go into?
if bacterial population low then virus enters lysogenic cycle bcos there’s few host for offspring to infect. lytic if many
what is vertical gene transfer
transfer of genetic material from parent to offspring
