Genetically Modified Organisms (GMO)
Fate and Transport of GMOs in the Environment
Recombinant DNA technology has been the key to developing improved varieties of plants. The genome modifications made possible by this process has made the modifications of plants virtually limitless. Instead of confining breeding to varieties within on species, plant reproduction can now be expanded to combining plant DNA with that of other species of plants, animals, or bacteria.
Genetic modifications of plants are done via one of two major processes:
1. The Ti Plasmid and Agrobacterium tumefaciens
The first method of plant genome modification involves the use of the bacteria Agrobacterium tumefaciens as the vector. This bacteria causes crown gall disease in plants which is characterized by uncontrolled growths (tumors or galls), normally at the base of the plant. The bacterial DNA molecule responsible for this tumor production is a circular plasmid called the Ti plasmid . A portion of this Ti plasmid (called the T-DNA) is inserted into a portion of the plant hosts DNA. By using this bacterial Ti plasmid as a vector, scientists can splice the DNA of interest (from other species) into the T-DNA of the bacteria and introduce it into the plant chromosome. The plant can then take on the qualities introduced to it through the spliced DNA, such as a crop with increased nutrients, stress tolerance, resistance to pests, etc (Griffiths, 1996).
The second method of genetic modification is through the use of the gene gun. Developed by plant scientists at Cornell University in the early 1980s, the tool allows scientists to inject isolated DNA directly into plant nuclei and tissues. When the gene gun is turned on, helium is released at a high pressure which ruptures a disk, sending a shock wave to another disk. Attached to the second disk are microscopic tungsten particles coated with thousands of the desired DNA molecules. When the shock wave hits the disk, the DNA molecules are shot into the target cells, thereby releasing the desired DNA so that it is incorporated by the chromosomes of the host plant (Voiland, 1999).
Although both of these methods of genetic modification eventually produce the desired result, they both have a high failure rate and thousands of attempts are needed to integrate new genes into the desired plants.
Versions of the techniques described for plant genetic modification can also be applied in several animal systems. Genetic modification in animals involves using one or more vectors such as Caenorhabditis elegans (a nematode), Drosophila (fruit fly), and mice. Once the gene of interest is isolated and obtained, the plasmid containing the gene can then be injected into the desired animal. Some of the advantages of animal gene modification are increased resistance, productivity, and hardiness of the animal (Griffiths, 1996). The animal may also produce better yields of meat, eggs, and milk.
The production and transport of genetically modified organisms continues to rapidly expand worldwide (figure). In 1999, almost 99% of the global area planted with GMOs was accounted for by three countries. The U.S. used 28.7 million hectares of land for GMOs (72% of the global area), Argentina used 6.7 million hectares of land (17% of the global area), and Canada used 4.0 million hectares of land (10% of the global area). The remaining 1% was accounted for by China, Australia, and South Africa. The global market for transgenic crops is projected to reach $8 billion US dollars in 2005 (Genetically Modified Food and Organisms, 2003).
The impact internationally of GMOs could result in great benefits for countries around the world, especially developing countries. The long-term benefits could include more sustainable agriculture and better food security for residents of developing countries. Increasing the amount of food produced per year could help the worlds ever-increasing population without using more land that would normally be used for other purposes, such as forestry. Genetically modified organisms could also have great benefits globally due to the potentially enhanced nutritional value of the genetically altered crops. For example, scientists have recently been able to create a strain of genetically altered rice to combat vitamin A deficiency, the worlds leading cause of blindness and malaise.
Despite the potential benefits of the transport of GMOs internationally, certain risks could also potentially exist. One potential risk is that GMOs could transfer genetic material to unmodified varieties, developing more aggressive weeds and threatening biological diversity in the world. A second potential risk is that when applied on a global scale, GMOs may fail to thrive in unexpected altered climatic conditions. And a third risk regarding the global impact of GMOs is that biotechnology of agriculture has the potential to concentrate control in the hands of a few farmers rather than help to relieve global food security problems caused by iniquity, poverty, and concentration of food production (Zarilli, 2000).
In the US, genetically modified crops are to be thoroughly evaluated for environmental safety before entering the marketplace. Most countries use similar risk assessment, although one concern especially for developing countries is creating uniform regulations and enforcing them. Countries are to address the following specific questions about their crops:
With the increasing globalization of the production and transport of GMOs, there also exists increasing debate about the impact and safety of GMOs in the environment. In certain areas, such as the European Union, there is mounting public resistance to the use of GMOs, which has resulted in a very limited expansion of GMOs imported to certain countries (Sample, 2003). Although the benefits seem as though they have the potential to enhance the products we consume, further investigation and monitoring of GMOs will be necessary in order to ensure their safety around the globe.