Genetically Modified Foods - The Specifics

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Genetically Modified Foods- The Specifics JoAnn Guest Jul 24, 2003 15:43 PDT

Genetically modified foods

 

 

Genetically-modified (GM) food has become a major health and

environmental issue. It has sharply divided opinion,

between those who believe the new technology will greatly enhance our

lives and those who fear it will prove a scientific " advance " too f

 

What is GM food?

How new is it?

When was it invented?

How does the technology work?

What are the potential health risks?

Are there health benefits?

Can we trust our food?

What are the green issues?

How do I know what I am eating?

Who controls GM food?

 

 

What is GM food?

 

Genetically-modified (GM) food is produced from plants or animals

which have had their genes changed in the laboratory by scientists.

 

 

All living organisms have genes written in their DNA. They are the

chemical instructions for building and maintaining life. By modifying

the genes, scientists can alter the characteristics of an organism.

 

We might, for examples, want to boost yields, increase muscle bulk

and make our crops and farm animals resistant to disease. Genetic

engineering holds these possibilities.

 

Some will argue that this new technology is " unnatural " .

 

Others will point to the commonality that exists between species - from

bugs and

worms to monkeys and humans, we already share many of the same genes.

 

 

How does this technology differ from what went before?

 

Farmers have been engaged in what we might term " traditional

genetics " for thousands of years. They have long understood that like

begets like, favouring the seed from plants with the most desirable

characteristics.

 

New plant types have also arisen by cross-breeding closely-related

species.

This is how we got oil seed rape.

 

But way genes are passed from one generation to the next through

sexual reproduction is something of a lottery.

 

Scientists have tried to speed things up by exposing experimental

plants to chemicals and radiation.

 

This has the effect of producing hundreds of mutations among the genes.

Some of these may be useful,

others will not and the plants will be discarded.

 

Genetic engineering, on the other hand, is more specific.

 

It allows scientists to select a single gene for a single

characteristic and

transfer that stretch of DNA from one organism to another - even

between different species.

 

An example of genetic engineering is the FlavrSavr tomato developed

by Calgene.

 

When tomatoes ripen, a gene is triggered to produce a

chemical that makes the fruit go soft and eventually rot.

 

Scientists have now modified the gene which has the effect

of " switching off " the chemical.

 

As a result, the FlavrSavr tomato softens more slowly, meaning it can

stay longer on the vine to

develop a fuller taste. Its longer shelf life also reduces waste.

 

When was GM food invented?

 

The first transgenic plant - a tobacco plant resistant to an

antibiotic - was created in 1983.

 

It was another ten years before the first commercialisation of a GM

plant in the United States - a

delayed-ripening tomato - and another two years

(1996) before a GM

product - tomato paste - hit UK supermarket shelves.

 

1996 was also the year that the EU approved the importation and use

of Monsanto's Roundup Ready soya beans in foods for people and feed

for animals.

 

These beans have been modified to survive being sprayed

with the Roundup herbicide that is applied to a field to kill weeds.

 

This soya, together with GM maize, is now used in a variety of

processed foods on sale in UK shops.

 

The products range from crisps to pasta.

 

A genetically-engineered version of the milk-clotting enzyme chymosin is

also used in cheese-making.

 

 

How does the technology work?

 

Scientists have developed a number of techniques for getting a

desired gene into a plant.

 

One technique makes use of a soil

bacterium, Agrobacterium tumefaciens.

 

This microbe, dubbed the " first genetic engineer " , has evolved the

ability to insert stretches of DNA into plants.

 

The bacterium does this to make plants produce the particular chemicals

it needs to

survive. Scientists get A. tumefaciens to deliver genes of their

choice.

 

Labs also use a technique called biolistics.

 

This uses a gun to fire the desired gene into a plant's cells.

 

The " foreign DNA " is carried on tiny pieces of gold.

 

With luck, the plant will take up the DNA and

start to read out its instructions.

 

Wheat and rice have been modified

in this way.

 

Another method relies on protoplasts.

 

These are plant cells which have had their tough walls removed.

 

This gives the foreign DNA easier

access to the cell interior.

 

All these techniques depend on the remarkable fact that many plants

can be regenerated from single cells or small pieces of plant tissue -

as all gardeners who take cuttings know.

 

This means a successful

modification can be multiplied very quickly.

 

 

Why do some people think this technology may be harmful to human

health?

 

Critics argue that we do not know enough about the way genes operate

and interact to be sure of what the outcome of any modification will

be.

 

They worry that the alterations could accidentally lead to

substances that are poisonous or trigger allergies.

 

The anti-GM lobby is critical of the use of DNA from plant viruses

and bacteria in the modification of crops -

 

they fear this may also

somehow trigger disease.

 

They have objected to the use of antibiotic-resistant marker genes in

transgenic crops, which are included by scientists to test whether or

not their main modifications have been successfully incorporated into a

plant.

 

The critics argue the antibiotic-resistant genes could be passed to

the micro-organisms that make us ill.

 

If this happens, we might not have the necessary drugs to fight back.

 

 

How do the genetic engineers counter these arguments?

 

They will tell you there is no evidence of any GM food on UK

supermarket shelves having caused any ill effects.

 

They make the point that very many of the conventional foodstuffs in

our supermarket have only got there after their non-GM, raw

ingredients have been treated to remove undesirable or toxic

substances - and that the regulatory structures that govern GM foods

are, in many ways, far stricter than for conventional products.

 

 

Bioengineers have also given us a new word to describe plants that

have been altered to have medicinal properties - " nutraceuticals " .

Back to top

 

So can we trust the food we eat?

 

Remember that we the consumers also have responsibilities. One of the

reasons food poisoning cases have risen dramatically in recent years

is because we have failed to store and prepare food properly in our

own kitchen.

 

What are the environmental concerns with GM crops?

 

The green lobby fears that some of the genes engineered into crops

could " escape " and be transferred to other species where they might

have adverse effects.

 

In particular, they are worried about genes that confer herbicide and

insect resistance.

 

They believe leakage of these genes could result

in the emergence of " superweeds " and in the disappearance of familiar

species of insects and birds as food chains become damaged.

 

They accuse the biotech companies of trying to " handcuff " agriculture

by attempting to tie farmers into deals where they have little choice

but to buy the GM seed and the designer chemicals to go with it.

 

Some of the biodiversity issues will be directly tested in the large-

scale GM crop trials to be undertaken in the UK.

 

It can be argued

that the British countryside is already a " sick " place, where modern,

intensive farming methods have inflicted immeasurable harm on the

natural balance of things. The big question is whether the new

technology will exacerbate the problems.

 

 

How do I know what I am eating?

 

The UK Government, together with industry, is attempting to produce

better labelling of food - so that consumers know precisely what they

are buying, be it in a supermarket or in a restaurant.

 

The current rules state that GM food has to be labelled

unless " neither protein or DNA resulting from genetic modification

are present " .

 

In plain terms, this means the following: if a crop was modified to

alter the composition of a food ingredient, for example starch or

oil, then the food will have to be labelled - GM DNA or protein will

quite clearly be present in the food.

 

If the crop was modified to protect it from, say, insect attack and

no GM DNA or protein is present in the extracted and purified starch

or oil, the food will not have to carry a label.

 

In this instance, the starch or oil would be chemically identical to

those products that were obtained from " conventional crops " . This is

known as the concept of " substantial equivalence " .

 

The GM labelling rules should satisfy those who wish to exercise a

choice based on any perceived health threat, real or imagined.

However, the idea of substantial equivalence means the rules will not

satisfy those who object to GM foods on ethical or religious grounds.

 

They are still denied choice because there will be some foodstuffs on

sale without a label whose manufacture has involved genetic

modification at some stage in the production process.

 

In addition, all this presupposes that the tests used to

detect " foreign " DNA or protein are foolproof - some scientists argue

they are not.

 

This is one of the reasons why supermarkets are now going to sources

where the origin and purity of raw materials can be guaranteed.

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Where is GM food grown?

 

There are up to 500 small experimental sites in the UK, but all GM

food on sale in the UK has been grown aboard, much of it in the USA.

Back to top

 

Who is monitoring the safety of GM food?

 

There are European Union directives covering what are more generally

known as genetically-modified organisms (GMOs). In the UK

specifically, two committees offer advice to the government. They are

composed of university academics and industry experts. The Advisory

Committee on Releases into the Environment (ACRE) includes an

environmentalist and the Advisory Committee on Novel Foods and

Processes (ACNFP) has one consumer representative and an ethicist.

 

 

This page only gives a brief account of some of the main points in

the GM food issue. For more in-depth information see some of the

dedicated sites in our links section.

 

JoAnn Guest

mrsjo-

DietaryTi-

http://www.topica.com/lists/Melanoma

http://www.geocities.com/mrsjoguest/Melanoma.html

 

 

 

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