(Excerpt from: Assessing the safety and nutritional quality of genetically engineered foods by John Fagan)

This section presents technical arguments regarding the following three points: 1. The inability to predict and control the outcome of gene manipulations. 2. The mechanisms by which genetic manipulations can generate allergens in foods. 3. The mechanisms by which genetic manipulations can generate toxins in foods.

This section may be of primary interest to those wishing to understand the technical details regarding the impact of genetic engineering on food safety. The arguments presented in the final section of this paper, which discusses procedures for testing the safety of genetically engineered foods, are not dependent on the details presented in the present section. Therefore it is not necessary to absorb this section before moving on the section on safety testing.

1. The inability to predict and control the outcome of gene manipulations

In the previous sections we point out that it is not possible to fully control and predict the outcome of genetic modifications of food organisms. The basis of this inability can be traced to the following three things, which are discussed in detail below. a. The complexity of even the simplest food-producing organisms makes it impossible to predict the full range of effects resulting from changing even a single gene. Thus recombinant genes have unpredictable effects on the characteristics of the genetically engineered organism and the food it produces. b. Recombinant DNA manipulations induce mutations at random locations within the genome of the recipient organism. These mutations have unpredictable effects on the characteristics of the genetically engineered organism and the food it produces. c. Although structural genetic information is universal in its "meaning," regulatory genetic information differs in "meaning" depending on the cell type and type of organism into which it is introduced. Thus, the same regulatory genetic information will have different effects on the functioning of different organisms. Since these diverse effects have not been sorted our scientifically, the results from introducing a new gene into an organism cannot be fully predicted.

a) Biological complexity leads to the inability to control or predict the effects of recombinant DNA manipulations on food quality and safety An important contributor to the unpredictability of genetic engineering is the complexity of food-producing organisms. Whether we examine the simplest single-celled microorganism, or a human being, or the global ecosystem, we find a huge number of complex components. These take part in extremely intricate, coordinated interactions, all as part of one, vast, integrated living phenomenon.

Within any one of the trillions of cells that make up the physiology of a food-producing organism there is another vast world of complex subcellular structures, organelles, molecular networks, and metabolic pathways, each composed of a variety of biomolecules. All work together in an integrated, interdependent manner.

Because all of these components are interconnected in their functioning, changes do not happen in isolation. The effects of adding just one gene to the system will ramify throughout the whole system, potentially influencing every aspect of cellular functioning and thereby every aspect of the organism as a whole. Because of the complexity of the system, it is impossible for the genetic engineer to even begin to predict how that initially small change will influence the functioning of the cell, not to mention the physiology and behavior of the organism as a whole.

In such a situation, surprises are inevitable, and many of those surprises will not be advantageous. For food-producing organisms, this translates into the possibility of unpredictable changes in food quality and safety. The mechanisms by which genetic manipulations can lead to increased allergenicity and toxicity, described below, provide examples of such surprises.

b). Mutations through Recombinant DNA Manipulations. The second source of uncertainty regarding the effects of recombinant DNA manipulations stems from the extremely crude nature of current gene transfer techniques. The genetic information introduced into the organism may be precisely defined in sequence, but it is inserted at random into the genome of the recipient organism. Each insertional event is in fact a random mutagenic event. Stated another way, gene transfer as it is commonly done is a mutagenic process that can disrupt any of the processes in which DNA and RNA participate. The sites at which such mutations occur will be random. Therefore, there is no way to predict which gene or regulatory processes will be disrupted as a result of gene transfer-induced mutagenesis.

By inactivating or altering the expression of genes encoding enzymes that catalyze important biosynthetic processes, mutagenic events could alter the allergenicity of a food or make it toxic, as described in detail below. These mutagenic events could also alter the nutritional qualities of a food. Furthermore, by altering regulatory sequences present normally in the recipient organism's genome, the same variety of regulatory sequence-related problems described below could be generated.

It should be pointed out that with most gene transfer methods used in eukaryotes, this mutational process will occur, not just sometimes, but every time a recombinant gene is inserted into the genome of an organism. Each such insertional event disrupts some native DNA sequence. Many such disruptions will, fortunately, be silent or inconsequential. However, there is a finite chance that one of these will alter the structure or function of the organism in a manner that significantly influences the properties of the foodstuff derived from it. That is, genetic alterations have a finite probability of altering the properties of the organism such that the properties of the food derived from it will be hazardous to health. In most cases, the procedures used in modification of food-producing organisms insert, not one, but several copies of a gene into the genome of the recipient organism. Thus, multiple random mutagenic events may occur, greatly increasing the probability of a damaging some gene important to food quality.

The risks related to manipulating the genomes of food-producing organisms are inherent in the mechanisms by which recombinant DNA techniques bring about genetic change. These risks cannot be discounted by pointing to the FlavrSavr tomato (the first genetically engineered crop to be commercialized) and saying that there have been no problems with it and therefore other transgenics will probably be safe, too. Each transgenic food-producing organism will undergo different mutagenic events, and respond to the genetic information introduced into it differently, leading to the range of unexpected alterations described above. Therefore there is no scientifically valid justification for such extrapolations.

c. Ambiguities of Genetic Information. Genes contain two distinct kinds of information, structural and regulatory. Structural information specifies the amino acid sequence of proteins, and consists of the genetic code, which was elucidated in the 1960's. This code is, with a few exceptions, identical for all terrestrial organisms. Thus, the structural information contained in a given piece of DNA is predictable.

However, the story is quite different for regulatory information. Transcription, translation, replication, recombination, and other processes involving DNA and RNA are controlled by regulatory information encoded in DNA or RNA sequences. The regulatory "code" is much more complex and diverse than the structural code. Furthermore, it is different in different organisms, and is even different in different cell types of the same organism.

For instance, there are many examples in the molecular biological literature in which recombinant genes, characterized in one cell type, are expressed at 100- or even 1000-fold higher levels in another cell type from the same organism. Such differences cannot be predicted simply by knowing the nucleic acid sequence of a recombinant gene. The only way to know is to gather empirical information-to actually introduce the gene into the second cell type and examine the result. If this is the case for different cell types within a single organism, the level of unpredictability will certainly be as great or greater for cross-species transfers of the kind commonly carried out in agricultural genetic engineering.

The underlying mechanism involved in the "reading" of regulatory information is well understood. Regulatory proteins exist in the cell, each of which is capable of scanning DNA (or RNA) molecules. Each can recognize and bind to a single, specific nucleic acid motif. That binding reaction triggers biochemical events leading to modulation of a process such as transcription, translation, replication, recombination, etc. In any particular cell, a given sequence can influence one of these processes only if the protein that recognizes that sequence is also present. Since different regulatory proteins are expressed in different cell types and in different species, a given DNA sequence will function as a regulatory signal only in some cell types and some species, and not in others. Our knowledge of the "regulatory code" is extremely incomplete. Therefore we cannot examine the sequence of a nucleic acid molecule and predict its regulatory function in a given organism.

Inserting DNA sequences that possess unanticipated regulatory activities into the genome of a food-producing organism could disrupt any of the cellular processes in which DNA or RNA participate, including replication, transcription, translation, recombination, transposition. Disruption of transcription or translation could alter the level of expression or the timing of the expression of any protein that is normally expressed in a food-producing organism. This could alter the allergenicity or toxicity of the food derived from that organism, as described below, and could also alter its nutritional or other characteristics. Disruption or alteration of replication, recombination, or transposition mechanisms could, among other things, alter the plasticity or stability of the recipient organism's genome, leading to increased rates of mutagenesis and consequently to a range of problems, as described below.