For thousands of years, humans have been genetically enhancing other organisms through the practice of selective breeding. Look around you: the sweet corn and seedless watermelons at the supermarket, the purebred dogs at the park, and your neighbor's prize rosebush are all examples of how humans have selectively enhanced desirable traits in other living things.
The type of genetic enhancement that generates the most concern goes a step beyond selective breeding, however. Technology now allows us to transfer genes between organisms. For example, the tomato plant's beetle resistance relies on a gene from a bacterium (Bacillus thuringiensis), which scientists inserted into the tomato plant's genome. This gene, called cry1Ac, encodes a protein that is poisonous to certain types of insects, including the beetle.
How is this done? Gene transfer technology is simply a sophisticated version of a cut-and-paste operation. Once the desired gene is identified in the native organism's genome, it can be cut out, transferred to the target plant, and pasted into its genome. (The illustration to the right describes the "gene-gun" approach, which is one of several gene transfer methods.) Once the new gene has been introduced, the plant can be bred to create a new strain that passes the gene from generation to generation.