Planet Earth and Its Environment A 5000-million year

Blueprint of Life
Topic 23: Transgenic Species
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
 outline the processes used to produce transgenic species
and include examples of this process and reasons for its
Biotechnology is any technique that uses living organisms to
make products. As far back in recorded history as biblical times,
biotechnology was used. For example, yeast was used to bake
bread and for the fermentation of wine and the production of
People in ancient times were
unaware that they were
employing what we call
biotechnology. It was only when
Louis Pasteur discovered (in
1862) that fermentation is
caused by microorganisms and
is not an inorganic chemical
process that people became
aware that they were using
living things to make everyday
In modern times, biotechnology has come to be associated with
genetic modification (genetic engineering) of living organisms.
Modern biotechnology involves manipulating the DNA (genetic
material) of living organisms, to artificially combine specific
qualities of different organisms.
It is an advancement on the reproductive
technologies that we have already
discussed, as it allows specific desirable
genes to be moved from one species to
another. Genes can be ‘cut and pasted’—
removed from the cells of one organism
and inserted into the genome of another
organism, where they become part of the
new organism’s genetic make-up and are
passed on to its offspring. This has only
become possible with an advance in the
scientific understanding of the structure
and functioning of DNA.
A transgenic organism is one whose normal genome has
been altered by introducing a gene from another species
(transgene) into it in such a way that the organism can pass on
this transgene to its offspring during reproduction.
The creation of transgenic species has many applications,
 creating genetically modified foods with increased nutrients,
higher yields and which can be processed more easily
 introducing resistance to disease, pests and pesticides in
 treating disease
 reproductive technology
Note: Creation of transgenic species is considered to be a reproductive
technology only in cases where it increases the breeding
success of the
When an organism is genetically modified, this usually entails
adding a desirable gene to its DNA. Ideally, one would like to
ensure that when it reproduces, it passes this gene on to its
offspring, along with all of its other genes. The latter involves the
process of genetic engineering to create a transgenic species.
Simplified steps outlining how to
create a transgenic species
The simplified explanation is ‘cut, copy and paste’
1. ‘cut’: a gene for a favourable characteristic is removed from
the cell of an organism, using restriction enzymes
2. ‘copy’: multiple copies are made (called ‘gene cloning’)—
this step is usually carried out in bacteria
3. ‘paste’: the genes are inserted (injected) into an egg cell of
another species and after fertilisation become part of the
newly formed organism’s DNA
4. The egg develops into a mature organism (a transgenic
species) with the new gene ‘switched on’ to function.
Gene Delivery Techniques
There are four main ways of inserting the desired gene into the
genome of a species to be genetically transformed:
1. micro-injection of DNA directly into the nucleus of a single
cell—this is usually performed under an optical microscope to
introduce DNA into egg cells when creating transgenic
Gene Delivery Techniques
2. biolistics: methods of
mechanically delivering DNA
on microscopic particles into
target tissues and cells by
‘firing’ them from a gene
‘gun’; e.g. tiny gold particles
are used to coat the DNA,
which is then fired at the
target cells under high
pressure or voltage by a gene
Gene Delivery Techniques
3. electroporation: increasing the membrane permeability by
applying an electrical current
Gene Delivery Techniques
4. transduction by a viral vector:
DNA may be carried by vectors
such as an adenovirus, liposomes
or bacterial plasmids into cells.
These viral vectors may be
injected directly into the
bloodstream or may be delivered
by aerosol delivery (nasal spray or
oral aerosol for example, used in
trials of gene therapy for cystic
A gene for a fluorescent protein from
jellyfish is now used to determine
whether an individual has successfully
incorporated a transgene. The
fluorescent gene is used as a marker
and is attached to the desired gene that
will be inserted into prospective
transgenic organisms. The gene with
attached marker is injected into an egg
cell and the resulting offspring
fluoresce under certain lighting
This allows the biologist to
recognise immediately which
individuals have been
transformed. This marker has
been used in some instances to
create fluorescent creatures for
aesthetic purposes or even as
works of art.
Transgenic Cotton—(Bt cotton plants)
Bt cotton is an example of a
transgenic organism. In the 1990s,
CSIRO scientists in collaboration with
the US company Monsanto
extensively trialled the use of its
Ingard GM cotton, also known as Bt
cotton, which is a transgenic species.
Transgenic Cotton—(Bt cotton plants)
Over the years, traditional pesticides used on cotton plants had
to be made stronger and be applied more frequently to eradicate
insect pests such as the caterpillar of the Helicoverpazea moth, a
pest which destroys hundreds of millions of dollars worth of
cotton each year.
Transgenic Cotton—(Bt cotton plants)
With increased sprayings,
these caterpillars were
building up immunity to the
pesticides due to natural
 Bt cotton plants were
genetically modified and
contain a gene that codes for
the production of a protein
that kills the caterpillar of
the Helicoverpazea moth.
Transgenic Cotton—(Bt cotton plants)
The insertion of the Bt gene into the cotton plant has reduced
the need to use pesticides to kill these caterpillars, which is
better for the environment and reduces the development of
pesticide resistance in the caterpillars. The gene is called Bt
because it was originally taken from the soil bacterium, Bacillus
Transgenic Cotton—(Bt cotton plants)
While cotton growers in New
South Wales and Queensland
would normally spray their crops
numerous times in one growing
season, they now only spray
occasionally to eliminate sucking
insects and mites, using a narrow
spectrum pesticide that does not
wipe out beneficial insects (such
as ladybirds and wasps) in the way
the powerful, broad spectrum
sprays for Helicoverpazea used to.
Transgenic Cotton—(Bt cotton plants)
The Bt gene codes for the production of the toxic protein in an
inactive form that is harmless to humans and most animals, and
even to most insects. However, when the protein is eaten by a
caterpillar, it is converted by the digestive system into an active
form that kills the insect.
Production of Transgenic Cotton
First: Scientists cut normal cotton
seedlings into small pieces and
place them on a solid growth
medium where they grow into
calluses. After about six weeks
they transfer the callus cells to a
liquid medium where they are
given hormones to induce them to
grow into cotton plant embryos.
Production of Transgenic Cotton
Second: By genetic
engineering, the Bt gene is
extracted from a bacterium,
Bacillus thuringiensis, using
restriction enzymes.
Production of Transgenic Cotton
Third: The Bt gene must then be transferred to the cotton plant
embryos. This is done using a second bacterium as a carrier or
vector. This bacterium, called Agrobacterium tumefaciens, is
known to cause the disease crown gall in plants. This vector is
able to inject genes into other cells.
Production of Transgenic Cotton
The cotton plant embryos are dipped in a solution that contains a
mixture of the vector, Agrobacterium, and the extracted Bt
genes (which have recombined with the Agrobacterium genome), and the
vector bacteria inject the Bt genes into the cotton cells.
Production of Transgenic Cotton
Fourth: Once the gene is
inserted, the embryos
containing the Bt genes are
grown in tissue culture and are
then placed on another solid
medium and germinated into
small plants, which are planted
in pots and grown in
glasshouses. These plants are
now a transgenic species,
containing a gene from another
species in their genome.
Production of Transgenic Cotton
Cotton is a very difficult plant to
culture, but CSIRO scientists
have developed workable
techniques for growing three
varieties of cotton. In order to
increase the success of the
project, the scientists have
developed four different
insecticidal genes to use in the
cotton. However, the project has
been very controversial, with
critics claiming that it is doing
more harm than good.
Reducing the Risk of Resistance
Ingard, a cotton containing the product of a single gene, has been
replaced by Bollgard II cotton, which contains two inserted
genes and produces two lethal proteins against the caterpillar. It
is highly unlikely that the caterpillar will become resistant to
both genes.
Reducing the Risk of Resistance
In addition, cotton farmers plant
a ‘refuge crop’ of pea plants in a
field nearby, so that moths that
may have one recessive allele for
resistance to Bollgard II continue
to interbreed with moths who
feed on the ‘refuge crop’, to
reduce the chances of inbreeding caterpillars with
double recessive alleles, which
could confer resistance.
-Watch Bill Nye Video

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