Updated November 2013
Genetic engineering, or genetic modification, uses a variety of tools and techniques from biotechnology and bioengineering to modify an organism’s genetic makeup. Transgenics refers to those specific genetic engineering processes that remove genetic material from one species of plant or animal and add it to a different species. Due to the high similarity in genetic sequences for proteins among species, transgenic organisms are able to effectively assimilate and express these trans-genes.
Figure 1: The mule is a common example of a transgenic organism created when a horse and a donkey mate and produce offspring. Image courtesy Wade B. Worthen, Furman University, Biology Department.
The process of creating a transgene begins by isolating the gene of interest from a donor organism or selecting for purchase any of the thousands of known genes from massive online genomic databases. Once the gene is obtained, it is usually altered so it can function more effectively or be expressed more readily in the host organism. That gene is then combined with other genetic elements and introduced into a second organism (the host), at which point it’s known as a transgene. A transgenic organism is further defined as one that contains a transgene introduced by technological methods rather than through selective breeding. Hybrids are transgenic organisms created when reproductive cells from two species combine to form a single embryo (e.g., a mule is the offspring of a horse and a donkey); on the other hand, chimeras are created by artificially combining genetic material from two organisms into a single species.
Figure 2: Golden rice (right) compared to white rice. Image courtesy International Rice Research Institute (IRRI) via Wikimedia Commons.
The field of transgenics allows scientists to develop organisms that express a novel trait not normally found in a species; for example, potatoes that are protein rich, or rice that has elevated levels of vitamin A (known as â€œgolden riceâ€).1,2 Transgenics may be also used to save endangered species such as the American Chestnut tree, which is currently being repopulated by Chinese-American chestnut hybrids specifically engineered with a genetic resistance to the chestnut blightâ€”the deadly fungus that nearly decimated native populations in the early 1900s.3
Transgenic combinations may also include plant-animal-human transgenes, such as when the DNA of human tumor fragments is inserted into tobacco plants in order to develop a vaccine against non-Hodgkinâ€™s lymphoma.4 Researchers have similarly developed a flu vaccine using human DNA and tobacco plants.5 Other transgenic plants have been used to create edible vaccines. By incorporating a human protein into bananas, potatoes, and tomatoes, researchers have been able to successfully create edible vaccines for hepatitis B, cholera, and rotavirus, the latter of which can cause fatal bouts of diarrhea.6
Another recent transgenic plant project, known as the “glowing plant project,” incorporated a gene from a firefly into a houseplant, creating plants that display a soft illumination in the darkness. One of the proposed goals is to create trees that could illuminate streets and pathways, thereby saving energy and reducing our dependence upon limited energy resources; however, the public release of such plants has sparked a heated debate centered around potential environmental impacts of introducing highly genetically engineered plants into natural ecosystems.7
BioSteelÂ® is a high strength, resilient silk product created by inserting the genes from a silk-spinning spider into the genome of a goatâ€™s egg prior to fertilization.8 When the transgenic female goats mature, they produce milk containing the protein from which spider silk is made. The fiber artificially created from this silk protein has several potentially valuable uses, such as making lightweight, strong, yet supple bulletproof vests. Other industrial and medical applications include stronger automotive and aerospace components, stronger and more biodegradable sutures, and bioshields, which can protect military personnel and first responders from chemical threats such as sarin gas.9
Figure 3: Pigs may serve as a valuable source of organs and cells for transplantation into humans. Source: Impactlab.net.
Genetic engineering and transgenic combinations represent a significant aspect of current biotechnology research. Other examples include:
Xenotransplantation, or the transplantation of living tissues or organs from one species to another, is often seen as a potential way to alleviate the shortage of human hearts and kidneys. Pigs have a similar physiology and organ size, making porcine (pig) organs ideal candidates for transplantation into human recipients. Researchers are also exploring the use of cell transplantation therapy for patients with spinal cord injury or Parkinson’s disease.
Genetic manipulation of stem cells now includes the growth of tissues on a scaffolding, or a 3-D printer, which then can be used as a temporary skin substitute for healing wounds or burns. Tissue engineering is becoming a viable alternative in procedures that involve replacement of cartilage, heart valves, cerebrospinal shunts, and other organs.10
Commercial companies are deriving therapeutic proteins, such as monoclonal antibodies, from the milk of transgenic cows, goats, rabbits, and mice, and using them to administer drugs in treatment protocols for rheumatoid arthritis, cancer, and other autoimmune disorders.11,12
Clearly, genetic engineering and transgenics represent fields with myriad potential practical applications that are of value to patients and physicians, as well as potentially lucrative research and innovation streams for commercial and industrial consideration.
Transgenic biotechnology presents an exciting range of possibilities, from feeding the hungry to preventing and treating diseases; however, these promises are not without potential peril. Some of the issues that need to be considered are the following:
If the blending of animal and human DNA results, intentionally or not, in chimeric entities possessing degrees of intelligence or sentience never before seen in nonhuman animals, should these entities be given rights and special protections?
What, if any, social and legal controls or reviews should be placed on such research?
What unintended personal, social, and cultural consequences could result?
Who will have access to these technologies and how will scarce resourcesâ€”such as medical advances and novel treatmentsâ€”be allocated?
What, if any, health risks are associated with transgenics and genetically modified foods?13
Are there long-term effects on the environment when transgenic or genetically modified organized are released in the field?
Should research be limited and, if so, how should the limits be decided? How should the limits be enforced nationally and internationally?
Are there fundamental issues with creating new species?
Are species boundaries â€œhardâ€ or should they be viewed as a continuum? What, if any, consequences are there of blurring species boundaries?
Are chimeras and transgenics more likely to suffer than â€œtraditionalâ€ organisms?
Will transgenic interventions in humans create physical or behavioral traits that may or may not be readily distinguished from what is usually perceived to be â€œhumanâ€?
What, if any, research in genetic engineering should be considered morally impermissible and banned (e.g., research undertaken for purely offensive military purposes)?14
- Will these interventions redefine what it means to be â€œnormalâ€?
The Issue of Species Boundaries
Some individuals argue that crossing species boundaries is unnatural, immoral, and in violation of Godâ€™s laws, which presumes that species boundaries are fixed and readily delineated.15 However, several books and journal articles demonstrate that the concept of fixed species boundaries continues to be a hotly debated topic.16,17 Some bioethicists point out that a variety of species concepts exist: biological, morphological, ecological, typological, evolutionary, and phylogenetic, to name a few.18,19 All of these definitions of what a species is reflect both changing theories and the varying purposes for which individuals conceptualize and utilize different species.20 If species boundaries are simply a matter of a naming convention, and there are no truly fixed boundaries to cross, then many philosophical objections to transgenics are rendered less problematic.
Figure 4: Many plants and animals form hybrids in nature. Should these hybrids be considered separate species? Copyright 2013 by The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California. Used with permission. Source: http://evolution.berkeley.edu/evolibrary/article/evo_41
While the morality of crossing species boundaries reflects differing worldviews and is subject to disagreement there are, however, several known risks associated with the transplantation of cells or organs from animals to humans. For example, there is a small but significant risk of the transmission of usually fatal zoonotic diseases, such as bovine spongiform encephalopathy (aka â€œmad cow diseaseâ€), porcine endogenous retroviruses (PERVs) and Nipah encephalitis.21 The introduction of these diseases to the human population could have devastating consequences. As a result, the U.S. Food and Drug Administration (FDA) has banned xenotransplantation trials using nonhuman primates until the procedures have been adequately demonstrated to be safe and until ethical issues have been sufficiently publicly discussed. However, with the advent of stem cell tissue engineering and 3-D printing, xenotransplantation may quickly become outmoded, opening the doors to more complex social, ethical, and legal issues and discourses.22
Figure 5: Genetically modified crops (or GMOs) may pose long-term risks to the environment, such as damage to cultivated foods and non-target organisms, or large-scale ecological shifts. Image source: OneGreenPlanet.org.
In addition to the issue of species boundaries, there are other issues that need to be considered and discussed prior to large-scale acceptance and usage of transgenics and other genetic engineering research, including:
- the risks and benefits of the experimental use of animals;
- the risk of creating new diseasesâ€”for which there is no treatmentâ€”by combining animal DNA or human DNA with plant DNA;
- the potential long-term risks to the environment;
- the potential for increased suffering of transgenic organisms. Various bioethicists, environmentalists, and animal rights activists have argued that it is wrong to create animals that would suffer as a result of genetic alteration (for example, a pig with no legs) and that such experimentation should be banned.23
The Legal Implications of Transgenics
Several bioethicists have called for a ban on species-altering technologies that would be enforced by an international tribunal.24 Part of the rationale for this ban is the concern that such technologies could be used to create a slave raceâ€”that is, a race of subhumans that could be exploited. In April 1998, scientists Jeremy Rifkin and Stuart Newman, who are both opposed to genetically modified organisms (GMOs), applied for a patent for a â€œhumanzeeâ€ (part human and part chimpanzee) to intentionally fuel debate on the issues and draw attention to potential abuses. The United States Patent and Trademark Office (USPTO) denied the patent on the grounds that it violated the Thirteenth Amendment of the Constitution of the United States, which explicitly prohibits slavery.25
Although the USPTO has permitted the extensive patenting of bioengineered life forms, the question that was raised by Newman and Rifkinâ€™s application is one that will not easily be resolved: What constitutes a person? A genetic definition is not very helpful, given the variability of gene sequences between individuals. A species definition can be controversial, as mentioned earlier.26 If we look to specific characteristics for a definition, we are faced with the fact that humans share many characteristics with primates and other animalsâ€”so where do we draw the line?27
If we create a being that has the ability to speak and perhaps even reason, but looks like a dog or a chimp, should that creation be given all the rights and protection traditionally bestowed upon a person? Some bioethicists argue that the definition of â€œhuman beingâ€ should be more expansive and protective, rather than more restrictive.28 Others argue that more expansive definitions could minimize humanityâ€™s status and create a financial disincentive to patenting creations that could be of potential use. The question of whether the definition should be more expansive or restrictive will need to be considered as courts, legislatures, and institutions address laws regarding genetic discrimination.
Figure 6: The International Olympic Committee is one of multiple organizations that have expressed public concern about genetic engineering.
In a similar vein, the medical director of the International Olympic Committee (IOC) has expressed concern that athletes have started employing genetic engineering to get an edge over their competition.29 If individuals are willing to genetically manipulate their children to make them better athletes, then itâ€™s likely individuals will be willing to manipulate their children to better looking, more musically inclined, or whatever else might give them an advantage. Opponents of genetic manipulation argue that, by allowing this, we run the risk of creating a race of superhumans, changing what it means to be â€œnormalâ€ and increasing the ever-widening gap between the haves and the have-nots. Proponents of genetic manipulation argue that currently parents can and do give their children advantages by sending them to better schools or giving them growth hormones, and that banning genetic manipulation is a denial of individual liberties. These arguments also reflect the opposing philosophies regarding how scarce resources should be allocated.
Genetic engineering and transgenics continue to present intriguing and difficult challenges for 21st century scientists and ethicists, and education and meaningful, respectful discourse are just the beginning of what is required to tackle such complex ethical issues. Until we as a society or, perhaps, as a global entity can agree on what beingsâ€”human or otherwiseâ€”are worthy of moral and legal status and respect, we can expect intense cross-disciplinary debate and discussion as new life forms are created through science and medicine.
© 2013, American Institute of Biological Sciences. Educators have permission to reprint articles for classroom use; other users, please contact firstname.lastname@example.org for reprint permission. See reprint policy.