The invention: Experimental technique for creating exact duplicates of living organisms by recreating their DNA.
The people behind the invention:
Ian Wilmut, an embryologist with the Roslin Institute Keith H. S. Campbell, an experiment supervisor with the Roslin Institute
J. McWhir, a researcher with the Roslin Institute W. A. Ritchie, a researcher with the Roslin Institute
Making Copies
On February 22,1997, officials of the Roslin Institute, a biological research institution near Edinburgh, Scotland, held a press conference to announce startling news: They had succeeded in creating a clone—a biologically identical copy—from cells taken from an adult sheep. Although cloning had been performed previously with simpler organisms, the Roslin Institute experiment marked the first time that a large, complex mammal had been successfully cloned.
Cloning, or the production of genetically identical individuals, has long been a staple of science fiction and other popular literature. Clones do exist naturally, as in the example of identical twins. Scientists have long understood the process by which identical twins are created, and agricultural researchers have often dreamed of a method by which cheap identical copies of superior livestock could be created.
The discovery of the double helix structure of deoxyribonucleic acid (DNA), or the genetic code, by James Watson and Francis Crick in the 1950′s led to extensive research into cloning and genetic engineering. Using the discoveries of Watson and Crick, scientists were soon able to develop techniques to clone laboratory mice; however, the cloning of complex, valuable animals such as livestock proved to be hard going.
Early versions of livestock cloning were technical attempts at dupli-
See also Internet; Long-distance telephone; Rotary dial telephone; Telephone switching; Touch-tone telephone.
Further Reading
Carlo, George Louis, and Martin Schram. Cell Phones: Invisible Hazards in the Wireless Age. New York: Carroll and Graf, 2001.
“The Cellular Phone.” Newsweek 130, 24A (Winter 1997/1998).
Oliphant, Malcolm W. “How Mobile Telephony Got Going.” IEEE Spectrum 36, no. 8 (August, 1999).
Young, Peter. Person to Person: The International Impact of the Telephone. Cambridge: Granta Editions, 1991.
Ian Wilmut
Ian Wilmut was born in Hampton Lucey, not far from Warwick in central England, in 1944. He found his life’s calling in embryology—and especially animal genetic engineering— while he was studying at the University of Nottingham, where his mentor was G. Eric Lamming, a leading expert on reproduction. After receiving his undergraduate degree, he attended Darwin College, Cambridge University. He completed his doctorate in 1973 upon submitting a thesis about freezing boar sperm. This came after he produced a viable calf, named Frosty, from the frozen semen, the first time anyone had done so.
Soon afterward he joined the Animal Breeding Research Station, which later became the Roslin Institute in Roslin, Scotland. He immersed himself in research, seldom working fewer than nine hours a day. During the 1980′s he experimented with the insertion of genes into sheep embryos but concluded that cloning would be less time-consuming and less prone to failure. Joined by Keith Campbell in 1990, he cloned two Welsh mountain sheep from differentiated embryo cells, a feat similar to those of other reproductive experimenters. However, Dolly, who was cloned from adult cells, shook the world when her birth was announced in 1997. That same year Wilmut and Campbell produced another cloned sheep, Polly. Cloned from fetal skin cells, she was genetically altered to carry a human gene.
Wilmut’s technique for cloning from adult cells, which the laboratory patented, was a fundamentally new method of reproduction, but he had a loftier purpose in mind than simply establishing a first. He believed that animals genetically engineered to include human genes can produce proteins needed by people who because of genetic diseases cannot make the proteins themselves. The production of new treatments for old diseases, he told an astonished public after the revelation of Dolly, was his goal.
cating the natural process of fertilized egg splitting that leads to the birth of identical twins. Artificially inseminated eggs were removed, split, and then reinserted into surrogate mothers. This method proved to be overly costly for commercial purposes, a situation aggravated by a low success rate.
Nuclear Transfer
Researchers at the Roslin Institute found these earlier attempts to be fundamentally flawed. Even if the success rate could be improved, the number of clones created (of sheep, in this case) would still be limited. The Scots, led by embryologist Ian Wilmut and experiment supervisor Keith Campbell, decided to take an entirely different approach. The result was the first live birth of a mammal produced through a process known as “nuclear transfer.”
Nuclear transfer involves the replacement of the nucleus of an immature egg with a nucleus taken from another cell. Previous attempts at nuclear transfer had cells from a single embryo divided up and implanted into an egg. Because a sheep embryo has only about forty usable cells, this method also proved limiting.
The Roslin team therefore decided to grow their own cells in a laboratory culture. They took more mature embryonic cells than those previously used, and they experimented with the use of a nutrient mixture. One of their breakthroughs occurred when they discovered that these “cell lines” grew much more quickly when certain nutrients were absent.
Using this technique, the Scots were able to produce a theoretically unlimited number of genetically identical cell lines. The next step was to transfer the cell lines of the sheep into the nucleus of unfertilized sheep eggs.
First, 277 nuclei with a full set of chromosomes were transferred to the unfertilized eggs. An electric shock was then used to cause the eggs to begin development, the shock performing the duty of fertilization. Of these eggs, twenty-nine developed enough to be inserted into surrogate mothers.
All the embryos died before birth except one: a ewe the scientists named “Dolly.” Her birth on July 5,1996, was witnessed by only a veterinarian and a few researchers. Not until the clone had survived the critical earliest stages of life was the success of the experiment disclosed; Dolly was more than seven months old by the time her birth was announced to a startled world.
Impact
The news that the cloning of sophisticated organisms had left the realm of science fiction and become a matter of accomplished scientific fact set off an immediate uproar. Ethicists and media commentators quickly began to debate the moral consequences of the use— and potential misuse—of the technology. Politicians in numerous countries responded to the news by calling for legal restrictions on cloning research. Scientists, meanwhile, speculated about the possible benefits and practical limitations of the process.
The issue that stirred the imagination of the broader public and sparked the most spirited debate was the possibility that similar experiments might soon be performed using human embryos. Although most commentators seemed to agree that such efforts would be profoundly immoral, many experts observed that they would be virtually impossible to prevent. “Could someone do this tomorrow morning on a human embryo?” Arthur L. Caplan, the director of the University of Pennsylvania’s bioethics center, asked reporters. “Yes. It would not even take too much science. The embryos are out
there.”
Such observations conjured visions of a future that seemed marvelous to some, nightmarish to others. Optimists suggested that the best and brightest of humanity could be forever perpetuated, creating an endless supply of Albert Einsteins and Wolfgang Amadeus Mozarts. Pessimists warned of a world overrun by clones of self-serving narcissists and petty despots, or of the creation of a secondary class of humans to serve as organ donors for their progenitors.
The Roslin Institute’s researchers steadfastly proclaimed their own opposition to human experimentation. Moreover, most scientists were quick to point out that such scenarios were far from realization, noting the extremely high failure rate involved in the creation of even a single sheep. In addition, most experts emphasized more practical possible uses of the technology: improving agricultural stock by cloning productive and disease-resistant animals, for example, or regenerating endangered or even extinct species. Even such apparently benign schemes had their detractors, however, as other observers remarked on the potential dangers of thus narrowing a species’ genetic pool.
Even prior to the Roslin Institute’s announcement, most European nations had adopted a bioethics code that flatly prohibited genetic experiments on human subjects. Ten days after the announcement, U.S. president Bill Clinton issued an executive order that banned the use of federal money for human cloning research, and he called on researchers in the private sector to refrain from such experiments voluntarily. Nevertheless, few observers doubted that Dolly’s birth marked only the beginning of an intriguing—and possibly frightening—new topic in the history of science.
See also Amniocentesis; Artificial chromosome; Artificial insemination; Genetic “fingerprinting”; In vitro plant culture; Rice and wheat strains.
