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GENETIC MODIFICATION
Genetic modification involves altering an organism's DNA.This can be done by altering an existing section of DNA, or by adding anew gene altogether. A gene is a code that governs how we appear and
what characteristics we have.
GENETIC MODIFICATION IN PLANTS
Like animals, plants have genes too. Genes decide the
colour of flowers, and how tall a plant can grow. Like people, the
characteristics of a plant will be transferred to its children, the plant seeds,which grow into new plants. When a scientist genetically modifies a plant,they insert a foreign gene in the plant's own genes. This might be a gene
from a bacterium resistant to pesticide, for example. The result is that the
plant receives the characteristics held within the genetic code. Consequently,the genetically modified plant also becomes able to withstand pesticides. Not
only genetic modification can be used to change the plant genes.
Spontaneous changes, radiation, chemicals and traditional processing can
also alter the characteristics of a plant or animal. Spontaneous alteration of
genes takes place naturally and sometimes with no effect. A spontaneousalteration can lead to the development of both positive and negative
characteristics. The method is not particularly good if the intention is to
create specific changes.
Genetically modified plants are genetically engineered tocontain one or more genes of another species. The aim is to introduce a
new trait to the plant species which does not occur naturally in this species,
for example resistance to certain pests, diseases or environmental conditions,
or the production of a certain nutrient or pharmaceutical agent.
Genetically modified plants are often called "transgenic plants", as theycontain one or more transgenes from other organisms. However , this term
also includes plants in which the transgene was integrated by naturally
occurring processes.
There are two common approaches to genetically engineer plants: Mosttransgenic plants are generated by the biolistic method (particle gun) or by
Agrobacterium tumefaciensmediated transformation.
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In the Biolistic Method, DNA is bound to tiny particles of gold ortungsten which are subsequently "shot" into plant tissue or single plantcells under high pressure. The accelerated particles penetrate both the
cell wall and membranes. The DNA separates from the metal and is
integrated into the plant genome inside the nucleus. This method hasbeen applied successfully for many cultivated crops, especiallymonocots like wheat or maize, for which a transformation with the
help ofAgrobacterium tumefaciensis less suitable. A disadvantage of
this procedure is the damage done to the cellular tissue.
Agrobacteria are natural plant parasites, and their natural ability totransfer genes is used for the development of genetically engineered
plants. To create a suitable environment for themselves, these
Agrobacteria insert their genes into plant hosts, resulting in a
proliferation of plant cells near the soil level (crown gall). The geneticinformation for tumour growth is encoded on a mobile, circular DNA
fragment (plasmid). When Agrobacterium infects a plant, it transfers so-
called T-DNA to a random site in the plant genome. The bacterial T-DNA is cut out of the bacterial plasmid and replaced with the desired
foreign gene. The bacterium is used as a means of transporting
foreign genes into plants (vector).This method works especially well fordicotelydenous plants like potatoes, tomatoes, and tobacco.Agrobacteria are less suitable for introducing foreign genes to crops
like wheat and maize.
PROCEDURE
Genetic modification of plants occurs in several stages:
An organism that has the desired characteristic is identified.
The specific gene that produces this characteristic is located and cut
out of the plants DNA.
To get the gene into the cells of the plant being modified, the gene
needs to be attached to a carrier. A piece of bacterial DNA called aplasmid is joined to the gene to act as the carrier.
A type of switch, called a promoter, is also included with the
combined gene and carrier. This helps make sure the gene worksproperly when it is put into the plant being modified. Only a small
number of cells in the plant being modified will actually take up the
new gene. To find out which ones have done so, the carrier package
often also includes a marker gene to identify them.
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The gene package is then inserted back into the bacterium, which is
allowed to reproduce to create many copies of the gene package.
The gene packages are then transferred into the plant being modified.
The plant tissue that has taken up the genes is then grown into full
size GM plants. The GM plants are checked extensively to make sure that the new
genes are in them and working, as they should. This is done by
growing the whole plants, allowing them to turn to seed, planting the
seeds and growing the plant again, while monitoring the gene that has
been inserted. This is repeated several times.
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GENETIC MODIFICATION IN TOMATO PLANT
The tomato has been a symbol for genetically modified food for
many years. In 1994, genetically modified tomatoes hit the market in the US as thefirst commercially available genetically modified crop. GM tomatoes have since
disappeared.
This transgenic tomato (FlavrSavr) had a "deactivated" gene ( Antisense
approach). This meant that the tomato plant was no longer able to produce
polygalacturonase, an enzyme involved in fruit softening. The premise was thattomatoes could be left to ripen on the vine and still have a long shelf life,
thus allowing them to develop their full flavour. Normally, tomatoes are
picked well before they are ripe and are then ripened artificially.Scientists are still working with genetic tools to give tomatoes new traits like
resistance to insect pests and fungal and viral pathogens. Other projects aim
to enrich tomatoes with substances offering health benefits. All of theseproducts, however, are still many steps away from receiving authorisation.
For example:
Addition of fish gene in tomato plant
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Scientists have created a frost resistant tomato plant by adding an antifreeze genefrom a coldwater fish to it. The antifreeze gene comes from the coldwaterflounder, a fish that can survive in very cold conditions. This is how it was done.
The flounder has a gene to make an antifreeze chemical. This is removedfrom the chromosomes within a flounder cell.
The antifreeze DNA is joined onto a piece of DNA called a plasmid. Thishybrid DNA, which is a combination of DNA from two different sources, isknown as recombinant DNA.
The recombinant DNA, including the antifreeze gene, is placed in a bacterium.
The bacterium is allowed to reproduce many times producing lots of copies ofthe recombinant DNA.
Tomato plant cells are infected with the bacteria. As a result, the antifreezegene in the plasmid, in the bacteria becomes integrated into the tomato plantcell DNA.
Tomato cells are placed in a growth medium that encourages the cells to grow
into plants. Tomato plant seedling is planted.
This GM tomato plant contains a copy of the flounder antifreeze gene in everyone of its cells. The plant is tested to see if thefish gene still works. Is it frostresistant? Yes it is.
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BENEFITS OF GM IN PLANTS
Foodstuffs made of genetically modified crops that are currently
available (mainly maize, soybean, and oilseed rape) have been judgedsafe to eat, and the methods used to test them have been deemed
appropriate. These conclusions represent the consensus of the
scientific evidence surveyed by the International Council for Science
(ICSU) and are consistent with the views of the World Health
Organization (WHO).
However, the lack of evidence of negative effects does not mean that
new genetically modified foods are without risk. The possibility of long-
term effects from genetically modified plants cannot be excluded andmust be examined on a case-by-case basis. New techniques are being
developed to address concerns, such as the possibility of the
unintended transfer ofantibiotic-resistance genes.
A genetically modified purple tomato has been created, that in a pilot
test significantly extended the lifespan of cancer-susceptible mice fed the
new tomatoes compared to mice fed normal tomatoes.Scientists took genes from the snapdragon plant (Antirrhinum), inserted them
into tomato plants and grew purple tomatoes high in anthocyanins, pigments
that occur naturally at high levels in berry fruits
such as the blackberry, cranberry and blueberry. There is evidence that
anthocyanins protect against some cancers, cardiovascular disease, age-
related degenerative diseases, diabetes, obesity and other illnesses.
Researchers already knew about the health protective properties of
anthocyanins that occur in high levels in some edible plants, but were of the
opinion that the levels found in many commonly eaten fruits and
vegetables were not high enough to give the best health benefits.
Since most people do not eat the recommended 5 portions of fruits and
vegetables a day, they can benefit more if the fruits and vegetables they do
eat can be developed higher in bioactive compounds.
Tomatoes are the most logical choice as they are an everyday food already
containing high levels of another important bioactive compound, the
antioxidant lycopene. Another beneficial antioxidant found in tomatoes and
other food plants is flavonoids.
GM crops are more productive and have a larger yield.
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Offer more nutritional value and better flavor.
A possibility that they could eliminate allergy-causing properties insome foods.
Inbuilt resistance to pests, weeds and disease.
More capable of thriving in regions with poor soil or adverse climates. More environment friendly as they require less herbicides and
pesticides.
Foods are more resistent and stay ripe for longer so they can be
shipped long distances or kept on shop shelves for longer periods.
As more GM crops can be grown on relatively small parcels of land,GM crops are an answer to feeding growing world populations.
GM foods are safe. Changing a few genes here and there does not
make a crop toxic or dangerous.
DANGERS OF GENETICALY ENGINEEERED FOOD
Scientists can choose which genes to manipulate, but they don't yet
know where in the DNA to precisely insert these genes and they haveno way of controlling gene expression. Genes don't work in isolation,
changing a few could change the whole picture, with unpredictable and
different effects under different circumstances. It is not correct to tout genetically modified food without evaluating
the risks sufficiently. Or at least proving conclusively that there are norisks.
Many GM companies don't label their foods as being GM foods. Thereis concern about a GM bias affecting business. But not labeling is
wrong and unfair to the consumers who should have the right to know
what they are buying and indeed to decide whether they want to buyGM food or not. Even if health safety factors are not an issue, some
people might have moral or religious objections. They should not have
to eat GM food if they don't want to.
GM food will end food diversity if everyone starts growing the samestandardized crops.
Herbicide-resistant and pesticide-resistant crops could give rise to
super-weeds and super-pests that would need newer, stronger
chemicals to destroy them. GM crops could cross-pollinate with nearby non-GM plants and create
ecological problems. If this were to happen with GM foods containing
vaccines, antibiotics, contraceptives and so on, it would very well turninto a human health nightmare.
The claim of ending world hunger with GM food is a false claim. Worldhunger is not caused by shortage of food production, but by sheer
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mismanagement, and lack of access to food brought about by various
social, financial and political causes. The GM technology companies patent their crops and also engineer
crops so that harvested grain germs are incapable of developing. This
is not empowering to impoverished Third World farmers, who cannotsave seeds for replanting and have to buy expensive seeds from thecompanies every time. The new technology also interferes with their
traditional agricultural ways which may be more suited to their
conditions.
REFERENCE
http://www.brighthub.com
http://www.wikipedia.org
http://www.gmo-compass.orghttp://www.medicinalfoodnews.com
http://www.paraschopra.com
http://www.greenfacts.org
http://www.brighthub.com/http://www.paraschopra.com/http://www.paraschopra.com/http://www.brighthub.com/