There are three basic requirements
for Genetic engineering requires : the gene which is to be transferred, a host
cell where the gene has to be inserted, and a vector through which the transfer
of gene is made to the host cell .
Say, for example, the gene for
making insulin has to be inserted into a bacterial cell. Insulin is a naturally
occurring protein made by cells in the pancreas in humans and other mammals
which carries out the breakdown of complex carbohydrates(sugar) in the blood to
glucose. Diabetic people dont the ability to make insulin or they form
insufficient amount of insulin. So, the first step is to obtain a copy of
the insulin gene. This copy can be obtained from a natural source, or it can be manufactured in a
laboratory.
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The second step is to insert the gene of interest, here insulin
gene, into the vector. The term vector means any living or nonliving
particles which will carry the gene of interest from one organism or place to another.
The most common vector used in genetic engineering is a circular form of DNA
known as a plasmid. Endonucleases are the enzymes that are used to cut the
plasmid molecule open at almost any point as per the need of the
scientist. Once the plasmid has been cut open, ligase enzyme is used to ligate
the cut portion. This is done to attach the insulin gene itself to the plasmid
before the plasmid is reclosed. Thus formed plasmid is called the hybrid
plasmid which now contains the gene whose product (insulin) is desired. It can
be inserted into the host cell, where it begins to function just like all the
other genes that make up the cell in the following ways
1. Transformation
2. Conjugation
3. Transduction
4. Recombination
2. Conjugation
3. Transduction
4. Recombination
In this case, however, transformation
of the insulin gene is done to competent bacterial cells. In addition to normal
bacterial functions, the host cell also produces insulin, due to the
inserted gene.
- Transformation by
electroportation,
- Micro particle bombardment
technique for gene transfer,
- PEG (Polyethylene Glycol)
mediated gene transfer,
- Liposome mediated gene
transfer,
- Ultrasound mediated gene transfer
and
different plant viruses like
Caulimovirus and Gemini virus and bacteria like Agrobacterium can be
used for the process of gene transformation.
