viruses Flashcards
what is the structure of a virus?
nucleic acid surrounded by a protein coat
where must viruses reproduce?
inside of host cell
what are viruses?
very small infectious particle consisting of nucleic acid enclosed in a capsid
what is a capsid?
a protein shell enclosing viral genome, built from subunits called capsomeres
two structures of viruses?
helical or icosahedral
what are viral envelopes?
surrounds the capsids of influenza viruses
what is the viral replication cycle?
enters host cell, begins to manufacture viral proteins, makes use of host enzymes, nucleic acid and capsomeres spontaneously self-assemble into new viruses
what are repliacted cell phages?
the best understoof viruses. two alternative reproductive mechanisms
what is the lyctic cycle?
a phage replicative cycle that culminates on the death of the host cells
produces new pahges and lyses(breaks open) the host cell wall releasing viruses
what is the lysogenic cycle?
replicates the phage genome without destroying the host
viral dna molecule is incorporated into host cells chromosome
integrated dna = prophage
what are the two methods of bacteria defence against phages?
innate ( restriction modification system) and adaptive (CRISPR-Cas system)
what is innate method of protection against phages?
foreign DNA cut by restriction enzymes, bacteriums own DNA protected from enzymes by being chem modified
what is the CRISPR-Cas system for protection against phages?
use of repeat sequences, when phage enters cells its DNA is integrated between two repeat sequences. each spacer repeats correspond to DNA from previously onfected virus DNA. nucleases interect with CRISPR region and resulting RNA are cut inot pieces bound to Cas proteins
two types of RNA viruses?
single stranded; positive and negative
double stranded
what is a retrovirus?
use reverse transcription to copy RNA into DNA i.e. HIV
