Biology Reference
In-Depth Information
textbook on virology the reader is referred to
Fundamental Virology
, Knipe &
Howley, 2001). The general steps of virus replication are as follows:
1.
Attachment and penetration:
In general, animal viruses, insect viruses,
bacteriophages, and archaeal viruses bind to specific receptors on the
host cellular surface, which induces penetration or internalization of the
virus into the host cell. Plant viruses, in general, do not recognize specific
cell surface receptors; rather, they enter the cells through lesions that
are, for example, those caused by feeding insects.
2.
Uncoating:
Unpacking of the nucleic acids from the capsid and initiation
of a new replication cycle.
3.
Replication and protein expression:
Copies of the nucleic acids are
synthesized and coat proteins, as well as non-structural proteins, are
produced. The coat proteins then self-assemble into the capsid and
package the nucleic acid.
4.
Assembly:
Capsid assembly and maturation, and specific packing of the
nucleic acid into the capsid — generally performed with high precision.
Studying and understanding virus assembly is an important goal in
virology, structural biology, and nanotechnology. The self-assembly
process of viruses has been exploited in nanotechnology and is discussed
in Chapter 5.
5.
Escape:
The assembled particles are released from the infected cell,
either by cell lysis or by budding (the latter is typically the case for
enveloped viruses). The virus derives its envelope from the host cell
membrane during this step.
6.
Transfer:
Survival of transfer from the infected cell to the next target
cell. Transfer refers to cell-to-cell movement, as well as the transfer
from one host to another. Transfer between hosts is achieved in various
ways; some viruses are transferred by insect vectors, whereas others are
transferred from host to host via body fluids or aerosols.
.1.1 the Virus genome
Virus genomes are highly diverse in their nucleic acid composition. The
virus genome can be composed of either DNA or RNA. It can be linear,
circular, or segmented. The nucleic acid can be single-stranded or double-
stranded. Single-stranded genomes can be positive or negative sense, where
the
refers to the messenger RNA (mRNA) polarity of the nucleic acid
strands. Positive sense refers to the RNA sequence that can be directly
translated into a protein; it can also be called the coding strand. Negative
sense
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