Genetic engineering is the manipulation of the hereditary material of organisms at the molecular level. The hereditary material of most cells is found in the chromosomes, and it is made of deoxyribose nucleic acid (DNA). The total DNA of an organism is referred to as its genome. In the 1950s, scientists first discovered how the structure of DNA molecules worked and how they stored and transmitted genetic information.

Genetic engineering relies on recombinant DNA technology to manipulate genes. Methods are now available for rapidly sequencing the nucleotides of pieces of DNA, as well as for identifying particular genes of interest, and for isolating individual genes from complex genomes. This allows genetic engineers to alter genetic materials to produce new substances or create new functions.

The biochemical tools used by genetic engineers or molecular biologists include a series of enzymes that can "cut and paste" genes. Enzymes...