Genetically Modified Organisms (GMO)


Fate and Transport in the Environment

Exposure Pathway

Routes of Exposure

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


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Characteristics of Genetically Modified Organisms

Definition of GMO: A genetically modified organism (GMO) is an organism that has undergone a recombinant DNA procedure. Recombinant DNA technology involves the transfer of genetic material from one organism to another plant or animal. GMOs are also called transgenic organisms because genes have been transferred. Cloning is not the same as genetic modification because cloning involves replicating the DNA sequence of one organism without changing any genes within the DNA sequence. Genetic modification requires that genes within the DNA sequence be modified. Replication of genetically modified organisms is usually conducted via cloning to maintain the exact gene sequence desired.

The genetic engineering process utilizes viruses and bacteria most often to implant the desired gene(s) into the organism. The gene is surrounded by an activator that causes the gene to switch on or off when desired. The ability to activate or deactivate a trait is the driving force behind genetic engineering.

Genetic engineering is occurring within both plants and animals. Genetic engineering in plants is occurring for food crops, trees, grasses and flowers, industrial products, pharmaceuticals, and environmental remediation and conservation. Genetic engineering in animals is occurring in mammals, aquatic organisms, and insects.


Food Crops
Genetic engineering within food crops is done to create pest and disease resistance, improve crops, and improve product characteristics.

Pest and disease resistance: resistance to viruses, fungi, bacteria, insects and mites, and nematodes.

Crop improvements: herbicide tolerance and resistance, improved nitrogen utilization, hormone regulation, and increased yield.

Improved product characteristics: more nutrients, more anti-nutritional factors, fewer allergens, and more functional attributes.

Genetic engineering within trees is done to improve pest, disease, and herbicide resistance and improve product characteristics.

Pest, disease and herbicide resistance: resistance to viruses, bacteria, fungi, and disease.

Improved product characteristics: increase energy production, increase efficiency of pulp milling, straighter trees for lumber and building, modifying tree fruits to improve flavor and color.

Grasses and Flowers
Genetic engineering in grasses and flowers is conducted to improve herbicide, pest, and disease resistance, improve stress tolerance, and improve product characteristics.

Herbicide, pest, and disease resistance: help minimize the invasion of weed species and improve resistance to pests and disease.
Improve stress tolerance: enhance tolerance to heat, cold, and drought.

Improve product characteristics: bring to market new colors of flowers, long-lasting plants, and low mow grass.

Industrial Products
Genetic engineering is being conducted to produce proteins, biopolymers, plastics, fatty acids, oils, waxes, and dyes. These products are often developed in food products, so cross-contamination may occur.

Genetic engineering is being conducted to develop plant-produced and edible vaccines, antibodies, and therapeutic proteins.

Environmental Remediation and Conservation
Genetic engineering is being conducted to develop plants that remove heavy metals from contaminated soil. In addition, plants are being engineered to become biosensors to detect or monitor hazardous substances.


Genetic engineering in mammals in being conducted in mammals for basic research, to produce human proteins for medical therapy, and for xenotransplantation to increase the availability of organs for transplantation in humans. In farm animals, genetic engineering is being conducted to increase growth or weight gain, to alter milk properties to reduce lactose or increase shelf life, or increase disease resistance. Industrial products are also being produced within mammals, such as spider silk protein in goat milk.

Aquatic Organisms
Genetic engineering in aquatic organisms is focused on enhanced growth, stress resistance, disease resistance, and sterility (to control unintended release of GMOs into the environment). In addition, research is being conducted to reduce allergens, produce pharmaceuticals, and increase biosensitivity.

Insects are being genetically modified to control their population and to control the transmission of pathogens, such as malaria.

The genetically modified organisms will often look the same as their conventionally bred counterparts. Determining the gene flow of the genetically modified organisms will prove to be difficult.


Harvest on the Horizon: Future Uses of Agriculture Biotechnology. Pew
Initiative on Food and Biotechnology. September 2001.