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first steps in developing a bio-engineered product involve isolating
and characterizing the genes that are needed to produce the desired
traits in the organism. This may be as simple as identifying
the correct Bt toxin to control an insect pest or the much more
complex process of modifying the nutritional content of a staple.
The genes need to be placed into appropriate constructs – linked
to promoters which control when the gene is expressed and often
to a selectable marker to aid the transformation process.
The transformation process involves getting the genetic construct
stably integrated into the host cell genome and then regenerating
an intact organism from the transformed cells. Depending on
the species and often strain of the organism selected this
process may involve a vector organism – such as the soil
bacterium Agrobacterium tiumefaciens – or direct introduction
of the gene construct using physical means such as a “gene-gun”.
The transformation process is usually only very slightly successful
in that very few of the treated cells actually contain the
integrated genes. Thus there is a need to select only the transformed
cells and to regenerate intact organism from these cells only.
This entails the use of selectable marker
genes which give
the transformed cells the ability to grow while untransformed
cells do not. Commonly, this is by the use of resistance to
an antibiotic or a herbicide, but genes which allow the utilization
of an uncommon substrate are also used to give the transformed
cells a selective advantage.
Regenerating an intact organism from
the transformed cells involves tissue culture techniques and – again depending
on the species and strain transformed – can take a significant
amount of time and expertise. At this stage, molecular characterization
of the regenerated individuals is necessary and a number of
separate transgenic “events” are selected based
on the desired expression of the transgene. Further development
of these elite events is then required to develop products.
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