A GMO is "an organism that has been modified by the insertion of DNA by human intention. It is usually DNA, which has been modified or ‘engineered’ to suit a particular purpose (recombinant DNA is the same thing). The DNA can be from a foreign organism, from the same organism or it may be a sequence synthesized in a laboratory." (Lynn M. Hartweek, Ph.D., Agronomy Department, University of Wisconsin, Madison, May 1997)
GMOs are "made with techniques that alter the molecular or cell biology of an organism by means that are not possible under natural conditions or processes.(National Organic Standards Board.) For instance, a scientist could take a gene from a fish and insert it into a tomato plant, or plants can be engineered to produce their own pesticide.
There are two common procedures: Recombinant DNA, and Bioballistics
Scientists noted that viruses and bacteria's survive and multiply by invading a host cell and injecting their own gene material into it. The new genetic material then aligns with the host cells DNA and recombines the DNA chain. Hence, the birth of Recombinant DNA.
Recombinant DNA techniques use biological vectors like viruses and plasmids to infiltrate a target cell with foreign genes. Plasmids are small circular pieces of genetic material found in bacteria that have the ability to cross species boundaries. The circles can be broken and new genetic material added to them. New genetic material that is piggy-backed onto plasmids can move across microbial cell boundaries and insert the foreign genes next to the bacterium's own genes. Most times the bacteria incorporate the gene and begin to express (or produce,) the protein per the gene instructions.
Viruses can also act as vectors in genetic engineering. The virus is an infectious particle that contain genetic material to which a new gene can be added. The virus can invade a target cell in the process of infecting that cell, and the new gene is incorporated. The virus itself can be disabled so that while it carries a foreign gene into a cell, it will not instruct the cell to replicate itself a thousand times over.
In order for geneticists to find out if their new gene has arrived in the target cell, an antibiotic resistant gene marker is also attached to the vector. The cells are then flooded with antibiotics and the cells that survive are the newly modified cells. There is a great deal controversy regarding the use of the antibiotic resistant gene markers, because of the higher percentages of super-bacterias that are already plaguing the medical field due to the overuse of antibiotics.
The last bit of information attached to the gene
package is a viral promoter. A promoter is found in all genes
and enables a gene to produce or "express" the protein in which it is encoded
to produce. The most common virus promoter used is the Cauliflower Mosaic
Virus (CaMV). There is serious concern regarding the use of the CaMV, including
risks of activating dormant viruses within the target cell, or combining
with other viruses to form new formidable viruses.
(see: The Cauliflower Mosaic Virus promoter - a hazard in GE plants Maize Necrotic Virus - a result of CaMV promoter recombination?, Hazards of CaMV Promoter)
Bioballistics uses a sort of shotgun that
shoots a spray of metal slivers coated with genetic material to the interior
of the cell. Once the foreign genetic material is in the cell, it is transported
to the nucleus where it is incorporated among the host genes. It is currently
unknown where exactly the foreign gene will end up in the DNA chain, or
how it will react with the host DNA. This uncertainty has potential dangers
that may not surface in the plant until several generations later.