Until recently, the use of traditional breeding techniques between two very closely related species was the only means of transferring heritable characteristics from one to the other. The advent of recombinant technologies in the manipulation of deoxyribonucleic acid (DNA), however, made it possible to transfer genetic characteristics from any plant (or from any organism) to any other. The simplest method for accomplishing this transfer involves the use of a vector, usually a piece of circular DNA called a plasmid. The plasmid is removed from a microorganism such a bacterium and cut open by an enzyme called a restriction endonuclease, or restriction enzyme. A section of DNA from the plant donor cell that contains the gene for an identified desirable trait is cut from the donor cell DNA by the same restriction endonuclease. The section of plant donor cell DNA with the gene for the characteristic of interest is then combined with the open plasmid DNA, and the plasmid closes with the new gene as part of its structure. The recombinant plasmid (DNA from two sources) is placed back into the bacterium, where it will replicate and code for protein just as it did in the donor cell. The bacterium is then used as a vector to transfer the gene to another plant, where it will also be transcribed and translated.
See also: Early Crop Domestication
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