Genetically Modified Organisms (GMO)

Characteristics

Fate and Transport in the Environment

Exposure Pathway

Methods for Measuring Exposure

Strategies for Preventing Exposure

Methods for Monitoring in the Environment


Harmful Effects

Dose Response

Absorption, Distribution and Metabolism

Sites of Toxicity

Biomarkers of Disease

Risk Assessment

References

5103/5104 Home

Fate and Transport of GMO’s in the Environment

Plants

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
2. The Gene Gun

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 host’s 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 1980’s, 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.

Animals

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.

Transport

The production and transport of genetically modified organisms continues to rapidly expand worldwide (figure). In 1999, almost 99% of the global area planted with GMO’s was accounted for by three countries. The U.S. used 28.7 million hectares of land for GMO’s (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 GMO’s 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 world’s 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 world’s leading cause of blindness and malaise.

Despite the potential benefits of the transport of GMO’s internationally, certain risks could also potentially exist. One potential risk is that GMO’s 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, GMO’s may fail to thrive in unexpected altered climatic conditions. And a third risk regarding the global impact of GMO’s 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:

  • impact on non-target organisms in the environment
  • whether the modified crop might persist in the environment longer that usual or invade new habitats
  • likelihood and consequences of a gene being transferred unintentionally from the modified crop to other species

In addition to that assessment, countries need to label their products properly and consistently (Global Status of GM Crops, 2003).

With the increasing globalization of the production and transport of GMO’s, there also exists increasing debate about the impact and safety of GMO’s in the environment. In certain areas, such as the European Union, there is mounting public resistance to the use of GMO’s, which has resulted in a very limited expansion of GMO’s 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 GMO’s will be necessary in order to ensure their safety around the globe.

References

Genetically Modified Food and Organisms (2003). Retrieved September 28, 2003, from U.S. Department of Energy Genomes website

Global Status of GM Crops (2003). Retrieved September 28, 2003 from,

Griffiths, A.J.F., Miller, J.H., Suzuki, D.T., Lewontin R.C., and Gelbart, W.M. (1996). An Introduction to Genetic Analysis (6th ed.). New York: W.H. Freeman and Company.

Sample, I. GM Crops (2003). Retrieved September 28, 2003 from Guardian Unlimited website

Voiland, M. and McCandless, L. Development of the Gene Gun at Cornell (1999). Retrieved September 28, 2003, from New York State Agricultural Experiment Station website

Zarrilli, S. United Nations Trade Conference on Trade and Development (2000).