GM Foods
Gene Modified Foods - the answer or the problem for ther future?

The role of genes and DNA.
Plants and animals are made of cells. Each cell carries within itself its own blueprint so that when it reproduces, it makes a copy of itself.

If a cell in a plant leaf reproduced to create a root cell the plant would rapidly lose water through the root cell and not receive energy from the sunlight because of that rogue cell.

If our liver cells suddenly decided to reproduce and form different cell types, you would die of liver failure. In fact this is what happens in cancer patients; something alters the genes or cell blueprints to produce tumour cells.

Colour enhanced electron microscope image of prostrate cancer cells

That’s why cancer cells are not always identified by our immune system and cannot be eradicated like other disease tissue – the tumour cells are not foreign, they are our own cells.

Genes are tiny sections of chemical code on a DNA molecule, located iin the cells chromosomes.

Section through cell showing chromosomes

The DNA molecule looks like a ladder, twisted. Each rung on the ladder is a pair of amino acids – the chemical building blocks of life.

A tiny section of a DNA molecule

To reproduce, it ‘un-zips” down the centre of the rungs into two equal halves. They are not exactly the same, rather they are complimentary.

Un-zipping DNA Molecule image (upper left hand portion of the diagram)
Each side now attracts the missing amino acids (lower left portion of diagram) to form a new half and complete the ladder (right hand side of diagram), thus one ladder has now become two. Both are copies of the original

Species, Natural Variation and the Gene Pool
The process is not always exact, so variations can and do form. The new DNA molecule can have one or two different rungs from the parent. This is what we call “natural variation”.

In nature, if the variation does not harm the organism, the reproduction continues and the organism has gained a different attribute. This means that within a group of organisms (a population) there are variations in the gene code. This is referred to as the gene pool for that species. Of course if a variation is harmful to the organisation, the organisation dies. This natural variation is how species develops a natural immunity to diseases that would otherwise wipe out an entire population.

When the population drops to a certain low level, there is not enough variation within the gene pool and any disease can wipe out all the members in the population. Currently this is happening in Australia with the Tasmanian Devil population. They are afflicted with a cancerous facial tumor disease and their gene pool is so lacking in variations, that it is likely that this disease could wipe them out and they become extinct. We are frantically trying to find a vaccine to save the species from extinction.

Natural Selection
Imagine a disaster strikes our population. Let’s say a disease arises and infects us all. Because of the Natural Variation in the gene pool, some organisms will survive. The disease will not be as lethal to them because they are different. Our population will be decimated but those that are left when the disease has passed will all have the new variation and will breed. The subsequent generations will have a natural immunity. This process is called Natural Selection.

In Australia the rabbits have developed an natural resistance to
myxomatosis and are approaching plague proportions again.

Here in Australia we were plagued by rabbits, introduced by the settlers. We introduced a lethal rabbit virus, called myxomatosis and hundreds of thousands of rabbits died. Today we are again plagued by rabbits. Those rabbits that survived have bred and their offspring have inherited a resistance to myxomatosis. Now almost all our rabbits are resistant to myxomatosis.

Genes and Traits.
We know that sections of the DNA control certain traits like eye colour but we are still learning what much of the DNA actually controls. There are some genes that seem to do nothing, called recessive genes. There are others that react when they are combined with special genes from a partner. Thalassemia is a condition common in people with a Mediterranian heritage that behaves like this. The gene is harmless on it's own and is thought to be an evolution that was effective against maleria but if a recessive Thalassemia gene carrier partners with another recessive Thalassemia gene carrier the children can be born with a serious illness - Thalassemia Major.

So far we have isolated groups of pairs that form traits but recently we have also found groups that we thought formed one trait, also intereact with other groups to form different traits. We have no idea how many gene groups interect with how many other gene groups. For example one gene group could create brown eyes but reacting with another gene group, could produce brown eyes and a long nose. Together these two groups could react with a third, to create a resistance to chest infections. At the moment we are still learning what the first gene groups do. By altering genes, we could be adding or effecting those genes that could be helping the organism combat some disease. It is also possible that we could create a "safe" gene sequence that is only one step (or protein) away from creating a lethal cancer cell. This new supposedly safe strain of GM organism could also be totally immune to existing natural controls (because we modified the genes to do this) and when it mutates into the harmful strain, there is nothing that will stop it.

To put it simply, we know many of the outcomes of 1 to 1 gene reactions, a few 1 to two reactions but have no idea what the outcomes will be when we get reactions of 2 to 3 or several genes to many genes reactions. The possibilities are in their billions.

Gene Splicing
The outcome of all this is that we really don't know enough to alter genes at all. Current experiments are basically trial and error. We have a rough idea what the transplanted gene did originally and we transplant it into the new organism. This is done by infecting the organism with an engineered virus or bacterium that will infect the chromosome and target a tagged section of DNA, replacing an existing section of the original gene.
Do we really know what that segment we are going to remove, does?
How can we predict it's long term effect?

It might give our rice plant a pest resistance now but when it reproduces several generations later with a natural variant, it could also create a toxic form - say rice grains containing cyanates or botulinum toxin - both would be deadly. We can predict but there are often surprises, so we keep the new strain in quarantine and test it rigorously. This poses a serious and unpredictable risk to the environment if anything escapes that quarantine. It could have all sorts of recessive genes that we don't understand yet. Sometimes we can do too well too, as this case of drought and pest tolerant canola illustrates:

In Victoria where I live, I am next door to several canola farms. Canola is grown for the seed which is processed to extract the edible canola edible oil. It is important that no pesticides are used once the seed starts to form  It would contaminate the oil. Rainfall is fairly low some years, so a drought and pest resistant variation or strain was genetically engineered by the Monsanto Company. It was a very good performer and it was authorised for use here.

Canola field in Victoria Australia - GM canola has become a weed here.

Today you see it everywhere - lawns, roadsides, gardens and even in paddocks that have not been replanted with it. It is a pest today but because it is also a crop, we cannot declare it a noxious pest. Around my neighbourhood, the roadsides are yellow in summer, with canola flowers, which cannot be harvested, eradicated or controlled and wildlife that used to feed on the native grasses, are starving, unable to eat canola. Nothing eats it to control it. It was engineered to be unpallatable to it's predators and requires less water than it's competition.

This is the true danger of gene modification - the results of being too successful:

• We run the risk of removing a recessive gene that could be important in coping with a future environmental change.
• We could remove a recessive gene that could have an important outcome with the genes of mating organisims.
• We could create a "perfect pest" with no natural enemies and no controls.
• We could do such a good job that our new GM organism out performs competition and forces its competing species into extinction.
• We could create changes to the chemistry of the organisn that could trigger allegies in our consumers.
• While we can test the results in the laboritory, we cannot test it's effect on the environment and the foodchain.
• There is a risk some of the test organisms genes could accidentally escape and enter the natural environment gene pool during experimentation, especially with plants and pollen.

Already it is impossible to get corn in the USA that is not gene modified because the GM corn has crossbred with the non GM variety. In some areas of the USA it is rumoured that a similar cross contamination has occurred with peanuts and cotton. This is bad news for exports, many countries have a ban on GM produce.

The geneticists claim their mutations are sterile but natural variation in DNA replication means you can never be 100% certain. The film Jurassic Park was based on this concept - their re-engineered dinosaurs were suppoased to be sterile but were found to be reproducing.

If GM produce does hold the secret to feeding our increasing population, we don't know enough about genetics to dabble in GM products yet.

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