A prime example of traditional genetic biotechnologies is selective breeding of plants and animals. The rudiments of selecting plants and animals with desirable traits and breeding them under controlled conditions probably go back to the dawn of civilization, but the expansion of knowledge about genetics and biology in this century has developed selective breeding into a powerful and sophisticated technology. New molecular approaches like marker-assisted breeding (which enhances traditional breeding through knowledge of which cultivars or breeds carry which trait) promise to enhance these approaches even further.

Traditional breeding technologies have been immensely successful, and indeed are largely responsible for the high yields associated with contemporary agriculture. These technologies should not be considered passé or out of date. For multigene traits like intrinsic yield and drought resistance, they surpass genetic engineering.

This is because selective breeding operates on whole organisms-complete sets of coordinated genes-while genetic engineering is restricted to three or four gene transfers with little control over where the new genes are inserted. For the most important agronomic traits, traditional breeding remains the technology of choice.

Other traditional nongenetic biotechnologies include the fermentation of microorganisms to produce wine, beer, and cheese. Industry also uses microorganisms to produce various products such as enzymes for use in laundry detergents.

In an effort to find microorganisms that produce large amounts of enzymes, scientists sometimes treat a batch of organisms with radiation or chemicals to randomly produce genetic alternations. The process, called mutagenesis, produces numerous genetic changes in the bacteria, among which might be a few that produce more of the desired product.