Genetically modified organisms (GMOs) are living things whose DeoxyriboNucleic Acid (DNA) has been changed by humans using the techniques of genetic engineering. The mechanism for creating a GMO is called the recombinant DNA technique. It involves combining strands of DNA from different sources to create a new DNA molecule that has a different combination of genes than that which occurs naturally. The newly created DNA is then inserted into a living organism or an egg or sperm, resulting in a genetically modified organism.
There are two classes of genetically modified organisms, cisgenic organisms and transgenic organisms. Cisgenic organisms are GMOs that result from the combination of different strands of DNA, which all originate from the same, or very similar, species. All of the DNA used in the process comes from organisms that are very closely related, usually defined as organisms that are able to breed together. For example, DNA might be taken from a variety of wild oat that has some beneficial trait, such as a resistance to a certain kind of pest. This DNA could then be spliced into the DNA of a cultivated variety of oat in order to produce a new strain that desirable traits from both varieties.
Transgenic organisms are genetically modified organisms that include DNA from two different species. Transgenic microorganisms are the most commonly created transgenic organisms. The simple DNA of bacteria lends itself to relatively straightforward recombinant DNA methods.
There are many examples of transgenic microorganisms that are used in a variety of applications. Certain bacteria are genetically engineered to produce insulin for the treatment of human diabetes. Other bacteria are engineered for the production of blood proteins to aid clotting for the treatment of hemophilia. In agriculture, some transgenic microbes are used to stimulate better crop growth, and to produce toxic chemicals that inhibit the proliferation of certain crop pests.
GMO research is often considered controversial for a number of reasons. Ethical issues aside, the creation of genetically modified organisms, and their introduction into the environment, can have unforeseen impacts. The growth of genetically modified crops in agriculture may lead to the spread of such genetically modified organisms into the wider environment, as it is difficult to completely isolate organisms in outdoor fields. Pollen from a genetically modified crop can, for example, easily cross wide-open spaces, and potentially cause the genetically modified plants being grown to be crossed with an existing species in a neighboring field.