Genetic engineering is the artificial altering of genes. This usually takes the form of the insertion of alien genes into the genome of a recipient organism. Genetic engineering is also called recombinant DNA technology. This name is slightly more descriptive of the process, which is actually recombining the DNA of existing organisms into new organisms.

Before scientists had the ability to directly alter the genes of an organism, many attempts were made to change living organisms. At its simplest, these attempts involved selective breeding, whereby plants or animals with the desired characteristics were bred together to enhance those characteristics. The offspring not showing the required combinations were not used to breed again, whereas those showing them were bred again. Successive generations gave new combinations. Examples of this technique are the many different breeds of dogs that exist today. Selective breeding is a slow process, the exact...