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
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out of date.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.