basic concept part 2 Flashcards
steps in viral replication
- Attachment
- Penetration
- Uncoating
- replication
- assembly
- release
involves the interaction of viral
attachment proteins (VAPs) and specific host
-cell
receptor sites
attachment
can occur by a cellular mechanism
called receptor
-mediated endocytosis, which is
referred to as viropexis when viruses are involved
penetration
refers to the separation of the capsid from
the viral genome. It results in the loss of virion
infectivity
uncoating
process by which enveloped
viruses obtain their envelope and confers
infectivity to enveloped viruses
budding
(lysis of naked viruses or budding of
enveloped viruses
release of virus
It is preceded by
the insertion of virus
-specific glycoproteins into the
membranes of the host cell. It occurs most
frequently at the plasma membrane, but also
occurs at other membranes
budding
the
inside of the membrane becomes coated with
a virion structural protein called
matrix or M protein
occurs in the host-cell nucleus (except
for poxviruses) and is regulated by host cell DNAdependent RNA polymerases (`
transcription
occurs on cytoplasmic polysomes and is
followed by transport of newly synthesized proteins to
the nucleus
Translation
occurs after the synthesis of the
early proteins.
. Genome replication
a group of ribosomes bound
to an mRNA molecule like “beads” on a
“thread
polyribosome
occurs on cytoplasmic polysomes.
It may result in the synthesis of a large
polyprotein that is subsequently cleaved into
individual viral polypeptides
translation
Involves a viral-specified RNA dependent RNA polymerase for all viruses, except
retroviruses, which use a host-cell, DNA-dependent
RNA polymerase.
transcription
It results when surface antigens
from two related viruses enclose the genome of one
of the viruses.
phenotypic typing
occurs when
pairs or related viruses infect the same cell.
- Phenotypic masking
occur when two mutants of
the same virus or, less frequently, two mutants of
different large DNA viruses, infect the same cell
Complementation
occur when two strains of
a segmented RNA virus infect a cell.
. Genetic reassortment
can be constructed with recombinant
DNA technology and allow gene transfer into cells
viral vectors
. Phenotypic masking also known as
transcapsidation
ability of a given virus to productively
infect a particular cell
viral tropism
the virus and host cell enter into a
peaceful coexistence, both replicating independently
without any cellular injury, a condition known as
‘steady
state infection.’
presence of appropriate receptors on
the surface of the cell determines whether virus can
adsorb to it and the virus gets into the cell
Cellular factors
viruses kill the cells in which they
replicate, sometimes with characteristic appearances or
cytopathic effect
Cytopathic effect
