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What is GM?


What is genetic modification?

For thousands of years farmers and plant breeders have been changing crop plants to improve characteristics such as size, resistance to disease and taste. Plants which grow well, have a higher yield or taste better are selected and bred from. This is still the most widely used technique for developing new varieties of a crop, and is limited by natural barriers which stop different species of organisms from breeding with each other.scientist cutting a DNA helix

The GM lobby often claims that genetic modification (or genetic engineering) is no different from traditional breeding, because people have always sought to improve their crops. However this is a gross misrepresentation of what actually happens during genetic engineering. Genetic engineering is a technology which allows scientist to take genes from several different species and put them into another, for example inserting genes from a bacteria, a virus and an animal into a plant. This would never be possible with traditional plant breeding methods.

This changes the characteristics of the modified organism, for example it might make a plant more resistant to weed killers or the plant might start producing chemicals that are poisonous to insects.


What are genes?

All organisms, from viruses to humans, contain a unique set of instructions which set down how they develop, grow and live. These instructions are found inside cells on a long molecule called DNA. DNA is divided into small sections which control different aspects of the organism's growth and characteristics, and these sections are called genes. Very simple organisms such as bacteria may have a few thousand genes, while more complicated organisms have many more, for example, it has been estimated that maize has around 50,000 genes. In genetic engineering, DNA is cut up and genes are moved around from one organism to another.


Genetic modification - a haphazard process

Nobody understands the mechanisms by which genes, interacting with each other and the environment, express traits (or characteristics). Transferring DNA and genes from one organism to another is a fairly haphazard process. At present there is no way to control what happens - new genes are inserted at random into the genetic make-up of the organism1.

It is now known that genes are found in groups2, and that when you insert foreign genes they tend to end up in these groups. This means that the random process of inserting new genes has the potential to disrupt the native genes and how they operate. In fact, such disruptions are quite common - inserted genes can fail to work, behave in ways that aren't expected, or affect the functioning of native genes3.

GM Amoflora potatoesScientists have voiced concern that such disruptions could lead to unexpected toxins being produced, or to changes in the levels of nutrients and naturally occurring toxins4. There are examples of genetic modification changing plants in entirely unexpected ways. For example, when researchers in Germany tried to boost the starch content of potatoes using genes from yeast and bacteria, they found that the starch content actually fell and other, unexpected, compounds were produced5.


How is genetic modification different from traditional breeding?

Genetic modification is fundamentally different from traditional breeding. Traditional breeding methods only combine natural genetic material from the same or related species. Genetic modification involves taking foreign DNA or transgenes from several different species, creating a package and then inserting it into the target organism.

The transgenetic package typically consists of genes from a virus, a bacteria, and either a plant and/or an animal.

DNA from viruses is often used as a "promoter" to ensure that the genetically modified organism will fully "express" the other foreign DNA taken from one or more bacteria, plants and/or animals. This makes use of the ability of viruses to insert their DNA into that of a host organism.

DNA from bacteria is used in two ways. First, DNA from antibiotic resistant bacteria is often used as a "marker" to enable scientists to determine if their attempt to introduce the foreign DNA package into the target organism has been successful. If the new organism survives treatment with the same antibiotic, it is assumed that the rest of the modified DNA - including the DNA that will produce the desired traits - has been successfully taken up by the target organism.

The second way in which bacterial DNA is used is to introduce a desired trait. The most common use in crops involves the insertion of DNA from the soil bacterium Bacillus thuringensis (or Bt). Bacillus thuringensis produces a toxic substance that kills some insects. This is used in the so-called Bt crops to make them produce their own insecticides.

There is a risk that these genes could survive digestion and become active in the bacteria which live inside the human gut, potentially turning the animals or humans who eat the modified crop into living pesticide factories or creating superbugs - bacteria that are resistant to antibiotics.

GM pigs at an American biotech fair

DNA from plants and/or animals is inserted to introduce the desired new trait into the target organism. Examples include DNA taken from spiders introduced into GMO potatoes to produce artificial silk; DNA from the flounder fish (which produces a kind of natural anti-freeze in this cold-water species) introduced into GMO fruits to provide greater frost-resistance; and DNA taken from a worm introduced into cloned GMO pigs to make them produce large amounts of omega-3 fatty acids believed to stave off heart disease.

The biotech industry lobby's claims that GMOs are inherently safe rest on an outdated scientific model which views biological organisms as if they were inanimate robots with interchangeable parts. This ignores thirty years of new scientific insights which confirm that not only are living organisms extremely complex self-organising beings, but that thier DNA operates far more like an ecosystem than a car. It is widely recognised that tinkering with their genetic codes will result in metabolic and ecological impacts that can not be predicted.



1: Maessen, GDF. 1997. Genomic stability and stability of expression in genetically modified plants. Acta Botanica Neerlandica 46 3-24

2: Schmidt, T and Heslop-Harrison, JS. 1998. Genomes, genes and junk: the large scale organization of plant chromosomes. Trends on Plant Science 3 195-9

3: Op cit 1

4: OECD. 2000. Report of the Task Force for the Safety of Novel Foods and Feeds. OECD Council 17 May 2000.

5: Gura, T. 2000. Reaping the plant gene harvest. Science 298 412-414