viral genetics Flashcards
(30 cards)
what type of phages are lysogenic?
lambda phages
what is the term for a phage that has integrated into the host genome?
prophage or p1 phage (if in a plasmid form)
what prevents the lytic pathway from occurring?
lambda repressors
what are the three steps of a lambda phage integrating into the host genome?
- phage enters in a linear form
- cohesive ends combine to make a circular piece of dna
- exposes the att site to attach to the host genome
define induction
the change from the lysogenic to the lytic cycle
describe rolling circle replication
- 3’ end of dna is elongated
- 5’ end is elongated with primers
- 5’ end consists of concatemers of dna
- the ds concatemer is cut into genome sized lengths once long enough
describe the genome of polio (2 things)
+ ssRNA
- has a polyA tail and 5’ Vpg cap
how does polio get around having a polycystronic genome?
- encodes proteases within its genome
- makes one large polyprotein that self-cleaves
describe the replication mechanism of +ssRNA
+ssRNA genomic RNA acts as mRNA, which is translated into proteins
viral RNA replicase makes a -ssRNA strand to use as a template to make more genomic copies
name two examples of +ssRNA viruses
coronavirus and polio
name 3 examples of -ssRNA
rabies, influenza and ebola
what is the role of neuraminidase and hemagglutinin in influenza?
neuraminidase: cuts through the sugars in mucous to get into the respiratory tract
hemagglutinin: promotes fusion with the cell membrane to inject the viral genome
what is the replication mechanism of -ssRNA viruses?
- carry their own rna replicase to make a +ssRNA to mimic mRNA and make proteins
- rna replicase also makes +ssRNA to make -ssRNA copies
define antigenic drift
- gradual mutations in viruses
- create many closely-related viruses
- allows for reinfection
define antigenic shift
- significant changes to the viral genome due to reassortment
- results in a radically different strain
- is the cause of pandemics
why is simian virus 40 a polyomer virus?
it has overlapping genes
- 3 genes of the late region share one region
- dsDNA circular genome
does simian virus have its own enzymes?
no - it’s uses all host enzymes for replication
it also uses host cell histones for dna packaging
how is the hiv genome arranged?
- two identical +ssRNA strands
- long terminal repeats at either end of the strand, which codes for the 5’ cap and polyA tail
- gag, pol and env region
what three proteins does hiv carry?
reverse transcriptase, integrase and protease
what two viruses use proteases to cleave their polyprotein?
polio and hiv
define a virion
the extracellular form of a virus
what is the genome size of polio?
28 nm
what is the genome size of smallpox?
200 nm
what is the genome size of coronavirus (kbp)?
ans: 3..
30 kbp
