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plants, select progeny plants with thicker skins, cross them (through pollination) with tomato plants with other desirable traits, and, eventually, end up with thick-skinned tomatoes that breed true. A process like this involves luck as well as skill, takes an average of six to eight years of growing cycles, and can (and often does) result in a tasteless supermarket tomato. Other such manipulations created the full array of fruits, vegetables, and crops that make our food supply so abundant. It is safe to say that virtually all plants that constitute part of today’s food supply were genetically manipulated in one way or another. Traditional genetic manipulations permit the transfer of genes only between members of the same species or those that are closely related—apples and pears, for example. In contrast, agricultural biotechnology extends these techniques to address problems of efficiency, time, and species limits on transferable traits.

FIGURE 12. This advertisement for the benefits of Golden Rice is part of an industry public relations campaign to promote public acceptance of genetically modified foods; it appeared frequently in 2001 in publications such as the New Yorker, Scientific American, and the New York Times. The text fails to emphasize that the rice, which “could help alleviate more suffering and illness than any single medicine,” is not yet available.

Because both traditional plant genetics and biotechnology involve similar manipulations and because they both achieve the same result—insertion of new segments of DNA into a plant’s existing DNA—biotechnologists maintain that the plants they develop are no different from those produced in old-fashioned ways, and should not be viewed or treated differently by regulatory agencies or the public. As we will see (and as the appendix explains in further detail), the steps involved in creating a transgenic plant are numerous and complex, and they introduce DNA segments that may come from unrelated organisms. Do these differences matter? The response is no if one focuses on the similarities: DNA is DNA no matter where it comes from. The response is yes if one focuses on differences or the societal implications of the technology. Points of view govern such responses and lead to political controversy.

Golden Rice: The Science

Plant bioengineering is accomplished through recombinant DNA technology, through which the DNA segments that comprise a desirable gene from bacteria, for example, are inserted (recombined) permanently into the DNA of an entirely different organism—in this case, a plant. Scientists using recombinant techniques have created insect- and herbicide-resistant crops by taking genes from bacteria and transferring them to corn and soybeans. To develop Golden Rice, they recombined genes and DNA regulatory segments from daffodils, peas, viruses, and bacteria to induce rice to make beta-carotene in its endosperm—the white, starchy part of the grain. Rice, like all grains, consists of three principal parts: a surrounding sheath of nutrient-rich bran, an inner endosperm containing starch and a little protein, and an embryo, which draws on the energy and nutrients in the grain when it begins to grow into a plant (see figure 13). Rice makes small amounts of beta-carotene in its bran layers, but not in the endosperm. Most people just eat the endosperm, however, because millers remove the bran layers when they convert brown rice to white rice (which is why white rice in the United States is enriched with several vitamins and iron).

FIGURE 13. The metabolic steps through which plants make beta-carotene from precursor molecules, and animals convert beta-carotene to vitamin A. An enzyme carries out each step. Rice bran contains information for the complete set of enzymes to make beta-carotene, but some enzymes are inactive in the endosperm. To create Golden Rice, scientists obtain genes (DNA) for the missing enzymes from other plants and bacteria and insert them into the DNA of rice (see tables 12 and 16, pages 158 and 280).

Rice bran and highly pigmented fruits