Cloning

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nd pigs were first domesticated about 8000 years ago and through selective breeding have become main sources of meat for humans. Dogs and horses have also been selectively bred for thousands of years for recreational purposes. Over the past 20 years, genetic engineering has been revolutionized by a new technique known as recombinant DNA, or gene splicing, with which scientists can directly alter genetic material (Encarta, 03). Genes consist of the chemical deoxyribonucleic acid (DNA). In recombinant DNA, the DNA of one organism is joined to the DNA of a second organism to produce a recombinant DNA. When this recombinant DNA is spliced with another organism, it permanently changes the genetic makeup of that organism. Recombinant DNA techniques have transformed genetic engineering in plant and animal food production and medicine. In most cases, DNA cannot be transferred directly from its original organism, known as the donor, to the recipient organism, known as the host (Brennan ??). Instead, the donor DNA must be cut and recombined with a matching fragment of DNA from an organism that can carry the donor DNA into the host. In 1982 the United States Food and Drug Administration (FDA) approved for the first time the medical use of a recombinant DNA protein, the hormone insulin, which had been cloned in large quantities(Encarta, 05). Previously, this hormone, used by diabetics had been available only in limited quantities from hogs. Since that time, the FDA has approved other genetically engineered proteins for use in humans. Scientists also have employed recombinant DNA techniques to produce medically useful human proteins in animal milk(Clarke, 1211). In this procedure, the human gene responsible for the desired protein is first linked to specific genes of the animal that are active only in its milk-producing glands(Clarke, 1211). The egg of the animal is then injected with the linked genes. The resulting babies will have these linked gen...