GM issues | Dangers of GM|
Contents
A. Constructing genes can go wrong
B. Genetic transformation weakens
C. An infinite potential to produce toxins
D. Without soil, we have no food
E. Allergins can kill
F. Damaging the integrity of the species
G. References
A. Constructing genes can go wrong
Building complex molecules you can't see is an imprecise process.
| SCIENTIFIC OBSERVATION A1 In one of the simpler applications of genetic engineering, genetically transformed bacteria were used to produce a bovine growth hormone for injection into dairy cattle to boost milk production. Once on the market, independent research revealed that the hormone had a substitution in one of its constituent amino acids.(1) |
Genes instruct the cell to produce precise proteins needed to maintain the life processes. Proteins can consist of many thousands of amino acid building blocks. The substitution of a single amino acid, in even the largest protein, can mean the difference between a toxic and non-toxic, stable and unstable, biologically functional and non-functional product.(2)
| SCIENTIFIC OBSERVATION A2 The bacterium, Bacillus thuringiensis. can be sprayed onto crops where it exerts useful pesticidal properties and quickly decomposes. When plants are genetically transformed to make them produce a single chemical identified as being important in the bacterium's pesticidal ability, it has been found to bind to soil particles: In this form, it can exert a long-term toxic effects and disturb the soil ecosystem.(3) |
A single substance produced outside its native living context, will always be beyond the natural control mechanisms which would otherwise protect against damaging effects. The transfer of an isolated engineered gene into a host introduces such a substance.
| SCIENTIFIC OBSERVATION A3 A bacterium was genetically transformed four times to increase its production of L-tryptophan for commercial extraction and sale as a nutritional supplement. The presence of trace amounts of a toxic tryptophan derivative was responsible for 37 deaths and 1511 cases of crippling neurological disease in the U.S.A. alone. The question of how much the genetically transformed bacteria contributed to the disaster and how much an obviously inadequate purification process was to blame will never be answered because the bacterial culture was destroyed.(4) |
The imprecise nature of genetic transformation makes it impossible to recreate an identical organism, even using the same techniques. Every genetically transformed form of life has its own biology, unlike any natural life ever studied.
This principle has been endorsed by the U.K. Advisory Committee for Novel Foods and Processed who recognise that ''unintended effects arising from the insertion event'' could emerge when one GM plant is crossed with another.(5) Unintended effects arising when one GM plant pollutes another in the field does not seem to have been considered.
B. Genetic transformation weakens
In order to genetically transform plants, a huge number of separated cells growing in tissue culture are bombarded with copies of the artificial gene construct. For every ten thousand cells strong enough to resist invasion, one cell randomly incorporates the foreign material and becomes transformed.(6)
| SCIENTIFIC OBSERVATION B1 Genetically transformed oilseed rape was found to have much poorer over-winter seed survival than its parent strain.(7) |
The disruption to the life processes caused by the insertion of the foreign gene, plus the effect of being forced to produce an unnecessary and alien substance, place a strain on the genetically transformed organism:
| SCIENTIFIC OBSERVATION B2 Petunias, genetically transformed to produce a more marketable flower colour, were found to loose the colour when stressed by environmental factors and old age.(8) |
Increased susceptibility to stress is an inevitable consequence of genetic transformation. This is a route to crop failure.
| SCIENTIFIC OBSERVATION B3 "While there are some examples of plants which show stable expression of transgenic these may prove to be exceptions to the rule. In an informal survey of 30 companies involved in the commercialization of transgenic crop plants, which we carried out for the purpose of this review, almost all respondents indicated that they had observed some level of transgenic inactivation. Many respondents indicated that most cases of transgenic inactivation never reach the literature." (9) |
The sudden disappearance of an engineered trait will be catastrophic to the crop yield. Transgenic failures are not reported in the scientific literature.
C. An infinite potential to produce toxins
Every natural substance in the living organism can become toxic if it turns up in the wrong place at the wrong time or in the wrong concentration.
| SCIENTIFIC OBSERVATION C1 A yeast transformed with multiple copies of its own genes to boost fermentation accumulated a natural metabolite, methyl-glyoxal, in amounts that were toxic and capable of damaging DNA.(10) |
The disturbance of normal living processes by the genetic transformation of the cell is likely to lead to multiple metabolite imbalances. While acute toxic effects (as described in BOX A3) may be unusual chronic small doses of a toxin can produce profound long-term damage, especially to the developing foetus and infant (11), while the presence of a variety of toxins could have synergistic damaging effects.
| SCIENTIFIC OBSERVATION C2 Genetically transformed tobacco given a bacterial gene to produce gamma-linolenic acid, produced mainly the novel toxin octodecatetraenic acid.(12) |
Identifying an unknown toxin is like looking for a needle in a haystack when you don't even know what a needle looks like.
The trace toxin associated tryptophan from a genetically transformed source (see BOX A3) was only identified after a mammoth US-wide investigation. Finding it was only made possible because it caused a disease with highly specific symptoms and because the offending substance was supplied in precisely labelled bottles.
We won't be so lucky next time.
D. Without soil we have no food
The soil is a poorly understood complex of living, organic and inorganic matter in intimate association.(13) Its ability to support healthy plants depends on the constant and balanced cycling of life and matter.
| SCIENTIFIC OBSERVATION D1 A common, harmless root-zone bacterium was genetically transformed to produce ethanol for fuel from vegetable matter. Its effect in the soil was to displace the parent strain and promote root-feeding nematode pests while inhibiting plant growth and the soil fungi.(14) |
| SCIENTIFIC OBSERVATION D2 A bacterium genetically transformed to degrade a herbicide produced a substance highly toxic to soil fungi.(3) |
Catastrophic disruption of the soil ecosystem is a real possibility when genetic engineers try to get clever. These instances represent a short sharp wake-up call not to interfere in biological systems we don't understand. The slow erosion of soil fertility by successive waves of genetically transformed, self-replicating microbes cannot be reversed.
Known allergens can be identified because we have human serum from a previous reactant with which to test for them. Potential allergens can occasionally be identified because they contain chemical groups already recognised to be a commonly allergenic. Completely novel allergens cannot be identified until they arise.
| SCIENTIFIC OBSERVATION E1 "One major concern over transgenic foods is their potential to be allergenic, which has become a concrete issue since a transgenic soybean containing a Brazil-nut gene was found to be allergenic (see BOX F4). Recent studies suggest that allergenicity in plants is connected to proteins involved in defence against pests and diseases." (15),(16),(17) |
Genetic transformation is likely to stimulate the plant's immune system as a reaction to the 'invading' DNA. This effect could be multiplied if the engineered gene is, in addition, involved with the creation of an immune response to a pest .
F. Damaging the integrity of the species
To persuade man-made genes to enter the host genome, they have to be attached to pieces of DNA which will enable them to invade.
| SCIENTIFIC OBSERVATION F1 A plant normally self-pollinating dramatically increased its ability to donate pollen to nearby wild types after genetic transformation.(19) |
| SCIENTIFIC OBSERVATION F2 Test DNA fed to mice was found transiently in their white blood cells, spleen and liver. When it was fed to pregnant mice, the DNA was found in parts of the foetus.(18) |
Is it surprising that DNA designed to be mobile finds ways to move?
| SCIENTIFIC OBSERVATION F3 Viral DNA sequences which 'switch on' the engineered genes are added to practically all commercialized genetically transformed crop plants.(19) These viral sequences have been shown to recombine with natural disease-causing viruses in plants to cause the emergence of a much more virulent form.(20) |
This describes a likely route to an ''Irish potato famine'' on a global scale, and encompassing every single staple crop we grow (all of which have now been genetically transformed).
| SCIENTIFIC OBSERVATION F4 In an attempt to make it more suitable for animal feed, soya was genetically transformed with a gene from the Brazil nut to boost its methionine-rich albumin content. This substance is not known to be capable of causing any allergic reactions, but the transformed soya inexplicably gained a nut allergenicity.(21) |
The transfer of a single gene appears, in this case, to have conferred some additional, more subtle, nut characteristics to the soya. We don't know why.
In the present situation, we are transferring many genes from potentially pathogenic organisms into the plants of our food chain; for example, E. coli) genes are now present in genetically transformed maize which is a large part of our livestock feed. The recent discover that E. coli) 0157 has achieved its notorious toxicity by acquiring toxin genes from other species should perhaps make us wary of a genetic interference in our food which might confer a similar trait.(22)
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Doyle J.D. et at. (1995) Effects of genetically engineered micro-organisms on microbial populations and processes in natural habitats. Adv. in Appl. Microbiol. 40
Mayeno A. N. and Gleich G. J. (1994) Eosinophilia-myalgia syndrome and tryptophan production: a cautionary tale. TIBTECH 12 346-52
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Hails R.S. et at. (1997) Burial and seed survival in Brassica napes subsp. oleifera and Sinapis arvensis including a comparison of transgenic and non-transgenic lines of the crop. Proc. R. Soc. Lond. B 264 1-7
Meyer P. et at. (1992) Endogenous and environmental factors influence 35s promoter methylation of a maize A1 gene construct in transgenic petunia and its colour phenotype. Mol. Gen. Genet. 231 345-52
Finnegan J. and McElroy D. (1994) Review - Transgene Inactivation: Plants Fight Back. BioTechnology 12
Inose T. and Murata K. (1995) Enhanced accumulation of toxic compound in yeast cells having high glycolytic activity: a case study on the safety of genetically engineered yeast. Int. J. Food Science Tech. 30 141-6
Howard C.V. hazards to Food and Animal Feed. Expert evidence presented at the court case of 28 Greenpeace activists and AgrEvo, April 2000. From 'GM On Trial', Greenpeace.
Reddy S.A. and Thomas T.L. (1996) Expression of a cyanobacterial delta 6-desaturase gene results in gamma- linolenic acid production in transgenic plants. Nature Biotechnol. 14 639-42 i
Turner M.A. and Macgregor A.N. Impacts on the soil. Expert evidence presented at the court casè of 28 Greenpeace activists and AgrEvo, April 2000. From 'GM On Trial', Greenpeace.
Holmes T.M. and Ingram E.R. (1995) The effects of genetically engineered micro-organisms on soil foodwebs. Bulletin of Ecological Society of America 75/2
Ho M.W., Biology Department, Open University (UK). Statement prepared for Greenpeace for the World Food Summit 1996
Ho M.W. and Tappeser B. (1996) transgenic transgression of species integrity and species boundaries - implications for biosafety. Proceedings of Workshop on Transboundary Movement of Living Modified Organisms resulting from Modern Biotechnology: Issues and Opportunities for Policy-makers
Frank S. and Keller B. (1995) Produktesicherheit von krankheitsresistenten Nutzpflanzen: Toxikologie, allergenic Potential, Sekundâreffekte und Markergene Eidg. Forschungsantalt fùr landwirtschaftlichen Pflanzenbau, Zùrich
Doerfler W. and Schubbert R. (1998) Uptake of foreign DNA from the environment: the gastrointestinal tract and the placenta as portals of entry. Vien Klin. Wochenschr. 11042) 40-4
Bergelson J. et at. (1998) Promiscuity in transgenic plants Nature 395 September 3, 25
Ho M.W. et al. Risks of virus resistant transgenic crops. Paper presented to a Workshop on the Ecological Risks of Transgenic Crops, University of California, Berkely, 2-4 March 2000
Nordlee M.S. et at. (1996) Identification of a Brazil-nuallergen in transgenic soybeans. NEJM, March 14, 688-92
Perna N.T. et al. (2001) Genome sequence of enterohaemorrhagic Escherichia col) 0157:H7. Nature 409, January 25, 529-33
This briefing paper was produced by Genetic Engineering Network Scotland using as much scientific literature as could be accessed and read. It is not exhaustive, and will be subject to on-going amendments. The text was prepared with the non-scientific of our community in mind, and, to that purpose, our comments are intended to clarify the implications of the scientific observations described; scientists should be able to read the literature for themselves.
We welcome comments.