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The experiment at the center of the controversy seems, in many ways, unworthy of the hoopla. It is not the Jurassic Park-type cloning most people think of, in which genetic material from a mature individual -- or DNA from an extinct dinosaur -- is nurtured and grown into a living replica of the original. This is far beyond the reach of today's science. There is a vast difference between cloning an embryo that is made up of immature, undifferentiated cells and cloning adult cells that have already committed themselves to becoming skin or bone or blood. All cells contain within their DNA the information required to reproduce the entire organism, but in adult cells access to parts of that information has somehow been switched off. Scientists do not yet know how to switch it back on.
Nor does the Hall-Stillman experiment involve genetic engineering -- the cutting and splicing procedures by which DNA strands within the nuclei of cells are mixed and matched. In one kind of genetic engineering, scientists have inserted human genes into the DNA of bacteria in order to mass-produce insulin and other human proteins. They have also experimented with therapies that involve replacing genes in human patients who either lack those genes or whose genes are defective. The George Washington research required none of that. The cells were just copied with their genes intact -- a far simpler process. Simple enough, in fact, that agricultural researchers have used it to clone embryos from cattle, pigs and other animals for more than a decade.
What brought the research into the human arena was the rapidly developing field of in-vitro fertilization. In clinics popping up around the world, couples who have trouble conceiving can have their sperm and eggs mixed in a Petri dish -- and the resulting embryos transferred to the mother's womb. The process is distressingly hit-or-miss, though, and the odds of a successful pregnancy go up with the number of embryos used. In a typical in-vitro procedure, doctors will insert three to five embryos in hopes that, at most, one or two will implant.
But some couples cannot produce more than one embryo, perhaps because the man's semen is in short supply or the woman's ovaries are running out of eggs or do not respond well to hormone treatments designed to stimulate them into superovulating (producing large numbers of eggs on demand). A woman with only one embryo has about a 10% to 20% chance of getting pregnant through in-vitro fertilization. If that embryo could be cloned and turned into three or four, the chances of a successful pregnancy would increase significantly. This is the reason Hall and Stillman began experimenting with cloning. But they weren't trying, in their initial effort, to produce clones that would actually be implanted in their mothers and later born. The scientists said they just wanted to take the first step toward determining if cloning is as feasible in humans as it is in cattle. Working in George Washington's in-vitro fertilization clinic, they selected embryos that were abnormal because they came from eggs that had been fertilized by more than one sperm; these flawed embryos were destined for an early death whether or not they were implanted. Thus Hall and Stillman saw nothing unethical about experimenting with them, and they got permission to do so from the university.