2.1. Read the text below and find in what ways genetic engineering affects agriculture. Genetic Engineering (ge) and Traditional Breeding Methods: a Technical Perspective

by Dr Michael Antoniou, senior lecturer in molecular biology at one of London’s leading medical schools and 17 years experience in the use of genetic engineering leading to clinical application.

The aim of this article is to assess GE in agriculture from a technical and basic genetic viewpoint focusing in particular on plants and animals. We will see that technically speaking, the use of GE in agriculture is a crude and imprecise technology which bears no resemblance to traditional breeding methods for producing new varieties of crops and farm animals. Given this imprecision, the outcomes of using GE in food production both in terms of potential ill health and negative environmental impact, are far more certain. There would therefore also appear to be good scientific grounds for questioning the validity of using GE in agriculture especially when there are safe alternatives available.

In order to assess the validity of the claim that GE represents a natural extension of traditional breeding methods, it is important to know how GE (“transgenic”) plants and animals are produced.

GE Plants

As an example, let us see how GE soya was generated. The objective here was to introduce into the soya plants a gene from a common soil bacterium which would allow it to survive when sprayed with the herbicide Roundup. Clearly you cannot “cross” a bacterium with a plant. Therefore, the first step was to grow cells from soya bean plants on plastic dishes in the laboratory. Now, in order to allow the bacterial gene to be able to work once introduced into its new plant host, it had to be linked to a genetic switch combining parts from a cauliflower virus and petunias. (As we discussed above, the bacterial gene’s own switch will only work in the bacteria from which it came). This combination of cauliflower virus, petunia and bacterial DNA was then introduced into the soya bean cell growing on the dished in the laboratory. Most of the cells don’t take up the DNA. This is done using a genetic trick. The introduction of the bacterial gene into the soya bean cell for herbicide resistance was accompanied by a second gene which confers resistance to an antibiotic. The soya bean cells were then treated with the antibiotic. The few cells which had taken up the herbicide resistance: antibiotic resistance “maker” gene combination survived and flourished whereas the majority of the cells which had not taken up these genes were simply killed by the antibiotic.

Finally, by changing the conditions under which the soya bean cells are grown, the cells clump together to form what is called a callus which in turn starts to put down roots and sprout green shoots. They are planted to grow into fully mature plants, the plant which displays the best agronomic performance, in this case resistance to herbicide, is then selected for further development.

Another example which illustrates the extreme combination of genetic material that can be produced is the introduction of the “anti-freeze” gene from an arctic fish into tomatoes, strawberries and potatoes in hope of producing resistance to frost.

GE Animals

The generation of transgenic animals is a somewhat simpler, but no less artificial procedure. Fertilised eggs are first removed from the animal of choice. These eggs are then injected with the genes one wishes to engineer into the animal. The DNA injected eggs are then returned to the womb of a surrogate mother where they complete their development and are born in due course. Therefore, in marked contrast to traditional breeding methods, all transgenic plants and animals start life as individual or group of cells growing on a plastic dish in a laboratory.

It is evident from the procedure we just described that with GE there are no holds barred. GE allows the isolation, cutting, joining and transfer of single or multiple genes between totally unrelated organisms circumventing natural species barriers. As a result combinations of genes are produced that would never occur naturally.

Clearly GE represents a great technological advance. However, as we have already discussed, genes have evolved to exist and work in families. Therefore, the claim that reductionist approach of GE which moves one or a few genes between unrelated organisms is a precise technology, is highly questionable. Furthermore, the generation of transgenic plants and animals is currently an imperfect technique. Once injected into the cells of the organism, the introduced gene is randomly incorporated into the DNA of its new plant or animal. In fact the manner in which GE animals and plants are produced always selects for the splicing of the foreign gene into regions of the host DNA where other natural genes are trying to work. Given the interdependence of gene function within any grouping of genes, this random splicing of the foreign gene into the host DNA will always result in a disruption in the normal genetic order in the “string of pearls”. Therefore, GE of animals and especially plants, always result in a loss, to a lesser or greater degree, of the tight genetic control and balanced functioning which is retained through conventional cross breeding. The effects which can occur in host genetic function can produce a totally unpredictable disturbance. The resulting disturbance in biochemical function can unexpectedly produce novel toxins, allergens and reduced nutritional value. The proponents of the use of GE in agriculture argue that mankind has been selecting and manipulating plant and animal food stocks for millennia and that this new technology is simply the next stage in this process. However we have seen:

• Technically speaking, GE and traditional breeding methods bear no resemblance to each other.

• GE plants and animals start out their life in a laboratory culture dish.

• GE employs totally artificial units of genetic material which are introduced into plant or animal cells using chemical, mechanical and bacterial methods.

• GE always results in disruptions to the natural order of genes within the host DNA.

• GE also brings about combinations of genes that would never occur naturally.

Therefore GE foods possess new and unique safety considerations both in terns of health and to the environment. The availability of safe, sustainable, natural methods of breeding and husbandry utilising the many thousands of different varieties of a given food crop, makes the risks associated with GE food simply not worth taking. These risks are even less acceptable when one takes into account the fact that once released into environment, genetic mistakes/pollution cannot be recalled, cleaned up or allowed to decay like agrochemicals or a BSE epidemic, but will be passed on to all future generations independently.

Source: Living Earth. Режим доступа: http://www.psrast.org/mianbree.htm

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