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4.
Unpredictable effects
Current understanding
of the way in which genes are regulated is extremely limited.
Any change to the DNA of an organism at any point may well
have side effects that are impossible to predict or control.
- A gene coding
for red pigment was taken from a maize plant and transferred
into petunia flowers. 6Apart from turning white, the flowers
also had more leaves and shoots, a higher resistance to
fungi and lowered fertility.(1)
- Lignin is
the strengthening and protective substance of woody plants.
There are attempts being made to design genetically engineered
trees with reduced levels of lignin, in order to make them
easier to process and pulp for the paper industry. However,
a number of studies have shown that when the genes important
to lignin production have been manipulated, there have also
been unanticipated negative side effects, such as abnormalities
or stunted growth in the trees.(2)
As it is not possible
to insert a new gene with any accuracy, the gene transfer may
disrupt the tightly controlled network of DNA in an organism.
The new gene could, for example, alter chemical reactions within
the cell or disturb cell functions. This could lead to instability,
the creation of new toxins or allergens, and changes in nutritional
value.(3)
- Oilseed rape,
genetically engineered by Monsanto to have higher levels
of pro-vitamin A, also a significantly decreased level of
vitamin E, and an altered fatty acid composition.(4)
- When researchers
in the US compared the levels of phytoestrogens (hormone-like
substances in plants) between conventional soybeans, and
genetically engineered soybeans treated with Monsanto's
herbicide 'Roundup', they found that the phytoestrogen levels
in the GE soybeans were reduced.(5)
- A yeast was
genetically engineered for increased fermentation purposes.
This led to the production of a metabolite called methyl-glyoxal
in toxic and mutagenic concentrations.(6)
References:
1.
Meyer P., Linn F., Heidemann I., Meyer H., Neidenhof I., Saedler
H. (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., Vol. 231,
p. 345.
Tappeser B. (1990)
Gutachten zur wissenschaften Zielsetzung und dem wissenschaftlichen
Sinn des Freisetzungsexperimentes mit transgenen Petunien.
Oeko-Institut e.V., Freiburg.
2.
Piquemal J., Lapierre C., Myton K., O'Connell A., Schich W.,
Grima- Pettenati J. & Boudet A-M. (1998) Down-regulation
of cinnamoyl-CoA reductase induces significant changes of
lignin profiles in transgenic tobacco plants. Plant Journal,
13, 71-83
Lapierre C., Pollet
B., Petit-Conil M., Toval G., Romero J., Pilate G., Leple
J.C., Boerjan W., Ferret V., De Nadai V. & Jouanin L.
(1999) Structural alterations of lignins in trangenic poplars
with depressed cinnamyl alcohol dehydrogenase or caffeic acid
o-methyltransferase activity have an opposite impact on the
efficiency of industrial Kraft pulping. Plant Physiology,
119, 153-163.
Hu W.J., Harding
S.A., Lung J., Popko J.L., Ralph J., Stokke D.D., Tsai C.J.
& Chiang V.L. (1999) Repression of lignin biosynthesis
promotes cellulose accumulation and growth in transgenic trees.
Nature Biotechnology, 17, 808- 812.
3.
Fagan J. Assessing the safety and nutritional quality of genetically
engineered foods. http://www.psagef.org/jfassess.htm (as of
April 2001)
4.
Shewmaker C.K., Sheehy J.A., Daley M., Colburn S. & Ke
D.J. (1999) Seed specific overexpression of phytoene
synthase: increase in carotenoids and other metabolic
effects. The Plant Journal, 20 (4), 401 - 412)
5.
Lappé M.A., Bailey E.B., Childress C.C. & Setchell
K.D.R. (1999) Alterations in clinically important phytoestrogens
in genetically modified, herbicide-tolerant soybeans. Journal
of Medicinal Food, Vol. 1
6.
Inose T., 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: 141-146.
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