[For further information on the Electronic Forum on Biotechnology in Food and
Agriculture see the Forum website.
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Sent: 31 May 2002 16:41
Subject: 1: Fundamental considerations in hazard identification of GMOs
[Welcome to Conference 7 of the FAO Electronic Forum on Biotechnology in
Food and Agriculture !!
Thanks to Dr. Suzanne Wuerthele for this first message which deals with some fundamental considerations regarding GMOs versus conventionally-bred organisms.
Some general points about the conference: i) participants should introduce themselves briefly in their first posting to the conference
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iv) The conference runs for 4 weeks, until 28 June.
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We hope that the conference will be interesting, constructive and beneficial............Moderator]
Because GMOs are fundamentally different from conventionally-bred organisms, they raise novel concerns about their effects on ecosystems at the genetic level and about their behavior in ecosystems at the agricultural level.
GMOs are unique because they are created by recombinant DNA (rDNA) techniques. These processes intentionally introduce into a host species genes from organisms with which the host could never breed. This makes GMOs conduits for the transfer of exotic DNA to the host's genetic ecosystem (the gene pools of all the organisms with which it can breed). In contrast, organisms created by conventional breeding cannot transfer exotic genes because conventional breeding merely rearranges genes already present among compatible species.
While viruses also function as exotic gene conduits among incompatible species, rDNA techniques for the first time introduce this function to domesticated plants and animals, and thus raise questions about how to understand the hazards of GMOs to genetic ecosystems.
Secondly, identification of hazards of GMOs must also consider the desired behavior of the GMO itself because rDNA techniques create organisms with inherently unstable and unpredictable behavior. This unpredictability derives from the fact that rDNA techniques utilize a variety of genes removed from their natural regulatory controls, and create mutations in the transgenic host (a characteristic shared with certain other modern breeding technologies).
Transgenes are multiplied in number or are accompanied by promoters so that the products for which they code are expressed in high concentration. Often, transgenic products are not controlled temporally or anatomically, but are expressed throughout the host's tissues and life cycle. Moreover, the promoter genes used to activate transgenes may produce unintended effects by also activating host or retroviral DNA. In contrast, highly expressed traits in conventionally-bred organisms are under genetic controls characteristic of the organism.
Transgene insertions create frameshift mutations which may alter host DNA function and stability. Ideally transgenes are inserted into "quiescent" sections of the host genome, previously assumed to be non-coding regions. However, it is currently impossible to systematically identify "quiescent" regions of the genome, and place controlled numbers of transgenes in them. Thus transgene mutations may unexpectedly interfere with important gene function in the GMO as well as be passed to organisms with which it breeds. Finally, transgenic expression may be "silenced" by DNA repair mechanisms, making GMO performance unreliable. In contrast, DNA damage is not necessary for conventional breeding, and long empirical experience has been used to identify and eliminate many undesirable mutations resulting from conventional breeding.
When rDNA techniques employ promoters and other genetic elements derived from viruses there is a potential for these elements to combine with DNA from host pathogens to create novel diseases. While this phenomenon has been documented in conventional plants and animals, its probability is greater in GMOs grown on millions of acres and containing viral elements in every cell.
Suzanne Wuerthele, PhD, toxicologist
US Environmental Protection Agency (EPA)
e-mail: Wuerthele.Suzanne (at) epamail.epa.gov