genetic modification in plants

8/4/2019 Genetic Modification in Plants

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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.
http://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Cell_wallhttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Monocothttp://en.wikipedia.org/wiki/Plasmidhttp://en.wikipedia.org/wiki/Ti_plasmidhttp://en.wikipedia.org/wiki/Vector_%28epidemiology%29http://en.wikipedia.org/wiki/Vector_%28epidemiology%29http://en.wikipedia.org/wiki/Ti_plasmidhttp://en.wikipedia.org/wiki/Plasmidhttp://en.wikipedia.org/wiki/Monocothttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Cell_wallhttp://en.wikipedia.org/wiki/DNA


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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
http://www.gmo-compass.org/eng/glossary/132.antisense_technique.htmlhttp://www.gmo-compass.org/eng/glossary/132.antisense_technique.htmlhttp://www.gmo-compass.org/eng/glossary/41.enzyme.htmlhttp://www.gmo-compass.org/eng/glossary/41.enzyme.htmlhttp://www.gmo-compass.org/eng/glossary/132.antisense_technique.htmlhttp://www.gmo-compass.org/eng/glossary/41.enzyme.htmlhttp://www.gmo-compass.org/eng/glossary/132.antisense_technique.htmlhttp://www.gmo-compass.org/eng/glossary/132.antisense_technique.html


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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/

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