Or let us assume that a beet grower would like to plant earlier in order to reap a better harvest. Ordinarily he couldn't because the beets would freeze in the cold weather. Biotechnology comes into play when genes from fish that easily survive in cold water are transplanted into the beets. Such traits that are the result of single-gene transfers, however, have limited effectiveness. To alter more complex traits, such as growth rate or drought resistance, is quite another matter.
Modern science is still unable to manipulate whole groups of genes.
After all, many of these genes have not even been discovered yet. Even the limited genetic modification of crops fills biotechnology's proponents with optimism. They say that GM crops promise a new green revolution. Already, such crops have helped to hold down the cost of food production. Food plants have been fortified with a gene that produces a natural pesticide, eliminating the need to spray clouds of toxic chemicals over acres of crops.