Viruses Flashcards
main components of viral structure
nucleic acids (DNA or RNA) Capsid (houses DNA, has capsomere)
potentially have envelope
envelope
additional structure of viruses
can have spikes
spike important for attachment
HA
how is the envelope generated?
composed of host cell membrane (acquired during maturation or release)
mostly plasma membrane but can be Golgi
stages of viral life cycle
- attachment
- entry
- uncaring
- Biosynthesis (replicating genome, transcription/translation of proteins)
- Assembly, maturation, and release
which phase of viral life cycle allows you to distinguish viruses?
biosynthesis
can distinguish between retroviruses, double/single strand, DNA/RNA viruses
after double stranded DNA viruses are uncoated….
their genome goes to the nucleus (unique to DNA)
what is required for replication of double stranded DNA viruses?
must make more DNA
so you use DNA for transcription for transcription and translation for replication by viral RNA dependent RNA polymerase
for RNA viruses, does creation of DNA/RNA viruses occur?
no. this is unique to DNA viruses (no DNA in replication cycle)
what is unique about retroviruses?
reverse transcriptase, uses spikes to attach host cell
it takes RNA to create DNA
multiplication of retrovirus
nucleus contains 2 identical + strands of RNA
enters by fusion via spikes
uncaring releases reverse transcriptase, integrate, protease
reverse transcriptase copies vRNA to make double strand DNA
how to viruses cause cancer
bring their own oncogenes and insert into host genome
cause conversion of host cells proto-oncogenes
suppress or interfere with host tumor suppressor genes (alter cell regulation)
bind to tumors suppressor genes themselves
insert promotor/enhancer next to oncogene in cell
what is lysogeny?
when phage integrates into host cell DNA and exists as a prophage – stays until appropriate conditions occur (lytic)
allows it to be transferred to progeny
allows it to be transferred
lysogenic life cycle
phage DNA integrates into host DNA, gets copied when cell divides
triggers (i.e. UV light) triggers excision from host
lytic life cycle
activated via lysogenic cycle
directs synthesis of new phages until the cell lyses and releases new viruses into body
what type of horizontal gene transfer is seen by lysogenic cells?
transduction
type of bacteriophages undergo lysogeny?
temperate phages
give rise to specialized transduction
protein infectious particles are found in:
yeast, brain, sheep, cows
cause disease in their respective host, and can cause human disease
Prion in cows
BSE/mad cow disease
prion in sheep
scrapie
prion in humans
kuru
viruses differ from bacteria in that viruses:
a. don’t have nuclei
b. obligate intercellular parasites
c. filterable
d. not composed of cells
d. not composed of cells
what distinguishes chronic viral infection from latent viral infection?
a. remains in equilibrium
b. it can be reactivated by immunosuppression
c. viruses appear suddenly
d. infectious virus gradually builds up over long periods of time
d. infectious virus gradually builds up over long periods of time
reactivated = latent suddenly= acute
