8/12/2005

Horizontal Gene Transfer – The Hidden Hazards of Genetic Engineering

Genetic manipulation is way scarier than most people think: To be able to get a dog cloned, for instance, you need to insert the cloned dog's genes in another dog's eggs. Scientists do it by using some transportation agents that allow the genes to be cloned hitch a ride on them to get inside the egg cells of the strange dog. Those agents that give the ride are by definition very invasive and able to penetrate cells of different species. How can scientists be sure those agents won't keep on spreading mutated genes to other species? In a word, they can't. If it's any consolation, humans never knew the danger of their tools, since the first curious hominid grabbed a stick to pound his enemy.. -law


Genetic engineering involves designing artificial constructs to cross species barriers and to invade genomes. In other words, it enhances horizontal gene transfer – the direct transfer of genetic material to unrelated species. The artificial constructs or transgenic DNA typically contain genetic material from bacteria, viruses and other genetic parasites that cause diseases as well as antibiotic resistance genes that make infectious diseases untreatable. Horizontal transfer of transgenic DNA has the potential, among other things, to create new viruses and bacteria that cause diseases and spread drug and antibiotic resistance genes among pathogens. There is an urgent need to establish effective regulatory oversight to prevent the escape and release of these dangerous constructs into the environment, and to consider whether some of the most dangerous experiments should be allowed to continue at all.

Key words: antibiotic resistance genes, dormant viruses, CaMV promoter, cancer, naked DNA, transgenic DNA,
Transgenic pollen and baby bees

Prof. Hans-Hinrich Kaatz from the University of Jena, is reported to have new evidence, as yet unpublished, that genes engineered into transgenic plants have transferred via pollen to bacteria and yeasts living in the gut of bee larvae(1).

If Prof. Kaatz’ claim can be substantiated, it indicates that the new genes and gene-constructs introduced into transgenic crops and other transgenic organisms can spread, not just by ordinary cross-pollination or cross-breeding to closely related species, but by the genes and gene-constructs invading the genomes (the totality of the organisms’ own genetic material) of completely unrelated species, including the microorganisms living in the gut of animals eating transgenic material.

This finding is not unexpected. Some scientists have been drawing attention to this possibility recently(2), but the warnings actually date back to the mid-1970s when genetic engineering began. Hundreds of scientists around the world are now demanding a moratorium on all environmental releases of transgenic organisms on grounds of safety(3), and horizontal gene transfer is one of the major considerations.

Some of us have argued that the hazards of ‘horizontal’ gene transfer to unrelated species are inherent to genetic engineering(4). The genes and gene-constructs created in genetic engineering have never existed in billions of years of evolution. They consist of genetic material originating from bacteria, viruses and other genetic parasites that cause diseases and spread drug and antibiotic resistance genes. They are designed to cross all species barriers and to invade genomes. The spread of such genes and gene-constructs have the potential to make infectious diseases untreatable and to create new viruses and bacteria that cause diseases.
Horizontal gene transfer may spread transgenes to the entire biosphere

Horizontal gene transfer is the transfer of genetic material between cells or genomes belonging to unrelated species, by processes other than usual reproduction. In the usual process of reproduction, genes are transferred vertically from parent to offspring; and such a process can occur only within a species or between closely related species.

Bacteria have been known to exchange genes across species barriers in nature. There are three ways in which this is accomplished. In conjugation, genetic material is passed between cells in contact; in transduction, genetic material is carried from one cell to another by infectious viruses; and in transformation, the genetic material is taken up directly by the cell from its environment. For horizontal gene transfer to be successful, the foreign genetic material must become integrated into the cell’s genome, or become stably maintained in the recipient cell in some other form. In most cases, foreign genetic material that enters a cell by accident, especially if it is from another species, will be broken down before it can incorporate into the genome. Under certain ecological conditions which are still poorly understood, foreign genetic material escapes being broken down and become incorporated in the genome. For example, heat shock and pollutants such as heavy metals can favor horizontal gene transfer; and the presence of antibiotics can increase the frequency of horizontal gene transfer 10 to 10 000 fold(5).

While horizontal gene transfer is well-known among bacteria, it is only within the past 10 years that its occurrence has become recognized among higher plants and animals(6). The scope for horizontal gene transfer is essentially the entire biosphere, with bacteria and viruses serving both as intermediaries for gene trafficking and as reservoirs for gene multiplication and recombination (the process of making new combinations of genetic material (7)).

Horizontal Gene Transfer – The Hidden Hazards of Genetic Engineering

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