Modification of the properties of a given organism by the introduction of foreign DNA.
The introduction of foreign DNA succeeds by using viruses or some bacteria, which transfer their DNA to other organisms under natural conditions, or by specific mechanical methods. Stable transformations result in the integration of foreign DNA within the genome and in the subsequent transfer of this DNA to the next generation. DNA transformed in a transient way is lost after a certain time by the organism.
Proteins, which are encoded by the sequence of the foreign DNA, are produced by the transformed organism. This results in new properties of the organism, depending on the sequences transformed. In another approach, the foreign DNA can be used to switch off one or several genes of the transformed organism.