The transfer of DNA into plants has been common practice for over 20 years, and transgenic plants are now a burgeoning industry. In 2007, over 114 million ha (282.4 million acres) of transgenic crops were grown commercially in 23 countries, the most prevalent traits being herbicide tolerance, pest resistance, or both traits stacked together (James 2007). In the laboratory, one encounters a vastly greater diversity of traits, including disease resistance, stress tolerance, nutritional improvement, modified development, and the use of plants to produce specific, high-value molecules, such as secondary metabolites, chemical precursors, antibodies, vaccine subunits, and industrial enzymes. It is notable that in the majority of cases, the purpose of gene transfer into plants is to achieve a specific, desirable phenotype. Plants that fail to live up to expectations are routinely discarded so that the best performers can be nurtured.