Example of an artificial DNA construct used during the Scottish Farm Scale Evaluations

April 2011

Since the dawn of GM foods, much of the argument about their acceptability has revolved around the question of whether genetic transformation of an organism is “playing with nature” or, indeed, whether this even matters since human beings seem to be “playing with nature” all the time. One way to judge these questions, is to have look at what genetic engineers actually put into your food.

The GM oilseed rape which was trialled during the Farm Scale Evaluations in Scotland had been transformed with a DNA construct made up from something like this (if your brain starts going into overload reading this, just skip to THE END):
  • a piece of bacterial DNA for sticking one end of the construct into the host genome, joined to
  • a piece of man-made DNA for nothing, joined to
  • a piece of bacterial DNA for telling an anti-weedkiller gene (see two below) where it stops, joined to
  • a piece of man-made DNA for nothing, joined to
  • a piece of bacterial DNA which is an anti-weedkiller gene, joined to
  • a piece of plant DNA for telling the anti-weedkiller DNA to switch itself on only in green tissues, joined to
  • a piece of man-made DNA for nothing, joined to
  • a piece of bacterial DNA for telling a tissue-dissolving gene (see two below) where it stops, joined to
  • another piece of bacterial DNA (from a different bacterium) for telling a tissue-dissolving (see one below) where it stops, joined to
  • a piece of bacterial DNA which is a tissue-dissolving gene, joined to
  • a piece of plant DNA for telling the tissue-dissolving DNA to switch itself on only in the bits of the flower which bear the anthers (these produce pollen), joined to
  • a piece of man-made DNA for nothing, joined to
  • a piece of bacterial DNA for sticking the other end of the construct into the host genome

The plant containing this construct is mated with a second GM oilseed rape plant which contains another DNA construct very similar to the first, except that the tissue-dissolving DNA has been replaced by a piece of anti-tissue-dissolving DNA to prevent the pollen-producing parts from being destroyed in the offspring (or they wouldn't produce any seed in the final crop).

(THE END)

References to 'plant' and 'bacterial' DNA in the above don't mean that they were extracted from these organisms, nor that they are replicas of such DNA. They mean that the idea for that piece of DNA came originally from the study of such an organism. The artificial DNA constructed is an analogue which may have many alterations to make it suitable for use outside its source organism.

Out of twenty-six pieces of DNA, fourteen pieces are modelled on bacterial DNA and eight are man-made inventions. Only four are modelled on plant DNA: two of these are for destroying a man-made chemical weedkiller (which doesn't need to be used in the first place) one destroys healthy plant reproductive tissue and one prevents the latter destruction but is only needed because the destruction gene is present.

Besides the mish-mash of assorted bits of DNA strung together by the genetic engineer, the large proportion of bacterial DNA analogues in the constructs, such as those described above, has some uncomfortable implications. Many bacteria have a habit of swapping DNA between themselves and of absorbing and using the DNA they find lying around them in living or dead matter: this can result in genes moving 'horizontally' between unrelated individuals. The process of horizontal gene transfer is speeded up if the DNA in question has similarities to the bacterium's own DNA. Moreover, the similar DNA is known to be able to ferry unrelated DNA into the bacterium, so that the large proportion of bacterial DNA in artificial constructs might well deliver plants genes into microbes. The Institute of Science in Society has described genetic engineering as “nothing if not greatly enhanced horizontal gene transfer and recombination.”

The constructs described above, which appeared on the Public Register prior to the release of the oilseed rape crop into the environment, are models of what the manufacturer intended to put inside the plants. But it is becoming increasingly clear that some, if not all, man-made DNA becomes scrambled during the transformation procedure and can even acquire new bits of DNA or lose bits. So, what was really there?

Healthy, living organisms normally have ways of preventing foreign DNA getting into their genomes, and ways of correcting altered or damaged DNA should it arise. This is how they are able to stay healthy. GM plants are unable to do either, or they would reject the novel DNA, and wouldn't remain GM.

Now ask yourself, are we “playing with nature”, or trying to re-invent it?

We can certainly play with nature, but be assured nature won't play by our rules.

(Adapted from an article which appeared on GM-free Scotland in September 2005)

Source
  • Aventis CropScience Application for consent to release genetically modified rape, Refs 00/R33/7 and 00/R33/7S, July 2000

No comments:

Post a Comment

Thanks for your comment. All comments are moderated before they are published.