he three very effective modes of gene transfer Transformation, Transduction and Transfection
observed in bacteria fascinated the scientist leading to the development of molecular cloning.
The basic principle applied in molecular cloning is transfer of desired gene from donor to
a selected recipient for various applications in the field of medicine, research, gene therapy
with an ultimate aim of beneficial to the mankind.
Transformation: Transformation is the naturally occurring process of gene transfer which involves
absorption of the genetic material by a cell through cell membrane causing the fusion of
the foreign DNA with the native DNA resulting in the genetic expression of the received
DNA.
Transformation is usually a natural method of gene transfer but as a result of technological
advancement originated the artificial or induced transformation.
Thus there are two types called as natural transformation and artificial or induced transformation.
In natural transformation, the foreign DNA attaches itself to the host cell DNA receptor
and with the help of the protein DNA translocase it enters the host cell.
The presence of nucleases restricts the entry of two strands of the DNA, destroys a single
strand thus allowing only one strand to enter the host cell.
This single stranded DNA mingles with the host genetic material successfully.
The artificial or induced method of transformation is done under laboratory condition which is
either a chemical mediated gene transfer or done by electroporation.
In the chemical mediated gene transfer, the cold conditioned cells in calcium chloride
solution are exposed to sudden heat which increases the permeability of the
cell membrane allowing the foreign DNA.
The electroporation method as the name indicates, pores are made in the cell by exposing it
to suitable electric field, allowing the entry of the DNA.
The opened up portions of the cell are sealed by the ability of the cell to repair.
Transfection: One of the methods of gene transfer where the genetic material is deliberately
introduced into the animal cell in view of studying various functions of proteins and
the gene.
This mode of gene transfer involves creation of pores on
the cell membrane enabling the cell to receive the foreign genetic material.
The significance of creating pores and introducing the DNA into the host mammalian cell contributed
to different methods in transfection.
Chemical mediated transfection involves use of either calcium phosphate or cationic polymers
or liposomes.
Electroporation, sonoporation, impalefection, optical transfection, hydro dynamic delivery
are some of
the non chemical based gene transfer.
Particle based transfection uses gene gun technique
where a nanoparticle is used to transfer the DNA
to host cell or by another method called as magnetofection.
Nucleofection and use of heat shock are the other evolved methods for successful transfection.