Biotechnology is nothing new; humans have been manipulating other species' genetics to serve our needs and desires for thousands of years. Tomatoes, potatoes, corn, beer, poodles-none would exist as they do today without the deliberate, methodical, and at times questionable (poodles?), intervention of humans.
However, there are several important distinctions between the more recent techniques commonly referred to as "genetic engineering" or "genetic modification" and the techniques we employed in the several millennia before it was possible to combine the DNA of a flounder and a tomato plant. To collapse the distinction between these two branches of biotechnology is to muddy the debate over the possible ramifications of genetic engineering.
It's important to note that the term "genetic modification" is used in international laws to refer to the use of recombinant DNA techniques to transfer genetic material between organisms in a way that would not take place naturally. The term is also sometimes used incorrectly to refer to marker-assisted selection, in which genes are simply identified (tagged) and then manipulated via more traditional breeding methods.
The most immediate difference between traditional breeding and genetic engineering is that with traditional breeding, we are working with sex cells. We are deliberately mixing the gametes of one individual with those of another, in hopes of bringing out desired results of this sexual recombination. With genetic engineering, we are inserting the manually-remixed genetic material from one or more organisms into the genome of another, well outside the context of sexual reproduction as it is commonly understood.
With traditional breeding, we are able to select for aspects of genetic potential which already existed within a given species, or at most, between closely related species or genera. We are limited to working within existing contexts of genetic material. When we bring out a desired set of traits, resulting even in something as novel as a poodle, that possibility-however "unnatural" seeming-had always existed within the genetic potential of the species.
There are several reasons, described below, why genetic engineering may cause unpredictable interruptions of normal gene function. This unpredictability is demonstrated most readily by the vast difference in the production of viable offspring between the two processes. In traditional breeding, most of the offspring produced are viable, functional organisms, although they very well may not express the desired traits. Though advances in genetic engineering have decreased the relative number of failures, the process still requires a large number of attempts (and failures) before viable organisms are produced.
In brief, genetic engineering involves the deliberate insertion of a foreign sequence of DNA into the genetic makeup and expression of an existing organism. One way to force a novel DNA sequence into a target genome is to coat it onto gold pellets and shoot it at a culture of host cells with a "gene gun." Another way is to perforate the cell membranes with chemicals or electricity, or to use bacteria to carry the sequence and infect the cells. In order to move, integrate and express the desired gene, the inserted DNA sequence must often include genetic segments modified from viruses and bacteria. The cells which survive the insertion process are screened for the expression of the desired sequences and grown out in an artificial culture using hormones. Those tissues/organisms which appear to function properly are then tested for commercial application. As compared to traditional methods of cross-pollination or animal pairing, genetic engineering is clearly a distinct process.
Further, common processes of gene insertion are still relatively crude, in that they inherently cause unpredictable mutations in the DNA of the host cells. This collateral damage can alter the functioning of the natural genes of the organism in random and potentially harmful ways. These processes were developed using a dated perception of the genetic landscape. It is now becoming clear that genes cannot be considered isolated units. They are connected to an extraordinarily complex whole. Unfortunately, we do not yet understand how all the pieces can fit and move together. A single change to the DNA can cause widespread changes in the organism which we cannot predict. Nor can we adequately predict how any given "GM" organism or sequence will interact, mutate or persist within a complex living ecosystem, once it is released from the laboratory environment.
The processes currently used to create commercial GM crops are not able to target where exactly the gene is inserted, nor can they ensure stable expression. GM sequences (or random fragments of them) can be randomly inserted into the middle of an existing gene or otherwise disrupt or alter normal gene regulation. The process of tissue culture itself can also be highly mutagenic. Unintended modifications due to such mutations (for example, the production of a new allergen or change in nutritional value) may not be detected or selected against by the genetic engineer before the GMO is put into commercial production and the public food supply.
With traditional breeding, the exchange of genetic material occurs between two organisms with a relatively similar recent evolutionary history. In this case, compatible mechanisms have evolved which are able to shuffle genetic sequences in a relatively controlled fashion, as compared to the more unpredictable gene insertion carried out with genetic engineering.
One final major difference worth noting in this brief review is the prevalent use in genetic engineering of marker genes which code for antibiotic resistance, employed to screen cells for expression of the transgene. This technique introduces risks associated with the creation of antibiotic resistant bacteria which do not exist with traditional breeding.
With genetic engineering, we are now capable of re-mixing genes from every kingdom of life and expressing them in ways that could never have possibly existed before. Nothing remotely similar to this could ever occur with the use of traditional breeding. As the commercial prevalence of genetic engineering increases and for the sake of meaningful public discourse about the possible health and environmental impacts, it is critical to maintain the distinction between these two branches of biotechnology.
Martin Dagoberto is Co-Founder and Network Facilitator of Massachusetts Right to Know GMOs, a state-wide network of safe food advocates supporting mandatory labeling of Genetically Modified foods.