Viral replication Flashcards
(44 cards)
what are the 3 main stages/phases?
eclipse phase,maturation and release phase, decay of viral progeny stage
what is the range of time viral replication can take?
large virus= 70hr bacteriophage=30mins
what is the eclipse phase?
time between infection and appearance of maturity in the cell (period virus is being uncoated)
what are the main steps in viral replication? (5)
1) enters cell
2) uncoating of DNA
3) replication for new DNA and protein synthesis for coat protein
4) assembly of progeny virus particles
5) exit from cell
what determines which cells can be infected?
different viruses recognize different cellular receptors (only small 5 of cells are targeted)
what is tissue trophism?
the cells and tissues that support growth of a bacteria or a virus (caused by tissues on cell surface that virus can recognize and bind to)
true or false: the type of receptor the virus can bind to is always related to the viral infection type?
False. Although some receptors are in places that seem relevent to the virus (e.g Influenza has respiratory tract receptors and polio has receptors in alimentary canal) the type of receptor a virus can recognise can also be down to chance.
what are the influenza receptors?
respiratory tract
where are the polio receptors?
alimentary canal
what two main mechanisms are used in host cell infection and disassembly?
fusion or endocytosis
what does HIV-1 retrovirus show wrt target cells?
cellular trophism that allows switching between target cells through mutation
what can HIV-1 infect? (2)
Macrophages and T-cells
what is a macrophage?
a large phagocytic cell found in stationary form in the tissues or as a mobile white blood cell
what are t-cells?
a lymphocyte of a type produced or processed by the thymus gland and actively participating in the immune response
where do most DNA viruses replicate? where do most RNA viruses replicate? exceptions:
most DNA viruses replicate in
the nucleus (except poxviruses)
most RNA viruses replicate in
the cytoplasm (except retroviruses)
outline RNA virus replication for ssRNA +
for + genome is mRNA so translation is direct –> can be translated directly to form capsid and RNA dependent DNAP which aids RNA synthesis –> assembly follows.
outline RNA virus replication for ssRNA -
Rna dependent RNApolymerase must be carried to synthesis mRNA then translation,protein production and more DNAP follows –> assembly
describe HIV host cell infection process. Fusion or endocytosis?
FUSION. virus binds to receptors on cell surface,triggering conformational changhe,leads to FUSION of cell membrane,capsid enters host cell,lipid protein left behind,uncoating follows.
MEMBRANE PROTEIN LEFT ON SURFACE OF HOST CELL
describe Influenza host cell infection process.Fusion or endocytosis?
ENDOCYTOSIS. virus binds to cell surface,surface binding receptor causes endocytosis, endosome in,endosome acidifies causing fusion and uncoating.
MEMBRANE PROTEIN BROUGHT INTO HOST CELL
what do HIV and influenza have in common wrt their structure?
the both have membranes with proteins on
describe polio host cell infection?
No membrane with protein, capsid binds directly to host cell,DOES NOT FUSE, virus is drawn in,conformational change,RNA genome enters through a pore
describe adenovirus infection process?
ENDOCYTOSIS. here capsid isn’t just for protection but the proteins bind directly to cellular receptors which triggers conformational change.Needs to get to nucleus through a pore
what type of virus is an Adenovirus?
DNA virus
what do sense - viruses have to have to make +RNA first?
polymerase in the viron particle
