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Should the cloning of human beings be prohibited

Should the cloning of human beings be prohibited?

Viewpoint: Yes, because of the potential physical dangers and the profound ethical dilemmas it poses, the cloning of human beings should be prohibited.

Viewpoint: No, the cloning of human beings should not be prohibited because the potential for medical accidents or malfeasance is grossly overstated, and the ethical questions raised by detractors are not unique to cloning—indeed, ethical questions attend every scientific advancement.

Since the birth of Dolly, the cloned sheep, in 1997, several reproductive scientists, including Severino Antinori, Brigitte Boisselier, and Panayiotis Michael Zavos, have announced that they were ready to clone human beings. However, cloning mammals is still a highly experimental technique. Scientists involved in cloning various mammals have reported many technical problems. A large majority of the clones die during gestation or soon after birth. Placental malfunction seems to be a major cause of death. Many of the surviving clones are plagued with serious physiological and genetic problems. During embryological development, cloned sheep, cows, pigs, and mice tend to become unusually large. Clones are often born with a condition called "large offspring syndrome," as well as severe respiratory and circulatory defects, malformations of the brain or kidneys, or immune dysfunction. It is not yet known whether clones will develop and age normally, or whether subtle failures in genomic reprogramming or genetic imprinting might lead to various defects. Theoretically, tissues generated from cells cloned from a patient's own adult nucleus should not trigger an immune response, but it is possible that subtle differences caused by the foreign cytoplasm in the donor egg might cause a rejection response. Although scientists at Duke University suggested that human clones might not experience the problems encountered in cloned animals, the risks remains very high and quite unpredictable. Eventually animal research may indicate that human cloning can be accomplished with no greater risk than in vitro fertilization posed when Louise Brown, the first "test-tube baby" was born in 1978. However, scientists generally agree that human reproductive cloning should not be permitted before the scientific and technical issues have been clarified.

Many scientists believe that, at least in the near future, experiments in human cloning would involve many failures, miscarriages, stillbirths, and the birth of deformed babies. Some observers think that the reckless claims made by some scientists stimulated the passage of premature Congressional legislation that would ban all human cloning, both reproductive and therapeutic (non-reproductive). Similar reactions have occurred in other nations. For example, the French and German governments jointly asked the United Nations to call for a worldwide ban on human reproductive cloning.

After a heated debate about human cloning, on July 31, 2001, the U. S. House of Representatives voted 265-162 to institute a total federal ban on human cloning. The bill included penalties of up to 10 years in prison and a $1 million fine. The House rejected competing measures that would have banned cloning for reproductive purposes while allowing nonreproductive or therapeutic cloning for scientific research. The emotional nature of the debate, and the lack of understanding of the scientific aspects of the subject, is epitomized by House Majority Whip Tom Delay (R-Texas) who declared: "Human beings should not be cloned to stock a medical junkyard of spare parts." On the other hand, Rep. Jim Greenwood (R-Pennsylvania) lamented that the House had missed an opportunity to balance potential biomedical breakthroughs with ethical concerns.

The Human Cloning Prohibition Act outlaws the process known as somatic cell nuclear transfer (SCNT) using human cells. Although this process can be used for reproductive cloning, as in the case of Dolly the sheep, the technique can also be used for non-reproductive or therapeutic cloning, a process that could be used to create cells and tissues that would be immunologically compatible with the donor of the nuclear material. The potential uses of therapeutic cloning include cures and treatments for many diseases. Cloned cells could be used to create replacement tissue for diseased hearts, pancreatic cells for diabetics, treatments for neurodegenerative diseases, such as Parkinson's and Alzheimer's, nerve cells for victims of spinal cord injuries, and skin cells for burn victims. Researchers, as well as leaders of biotechnology and pharmaceutical companies, believe that therapeutic cloning will result in major medical breakthroughs. Therapeutic cloning could provide valuable new means of testing drugs for safety and efficacy, thus streamlining and improving the drug development process.

Another modification of the nuclear replacement technique known as oocyte nucleus transfer could help women with defective mitochondrial DNA. Defects in mitochondrial DNA are known to cause more than 50 inherited metabolic diseases. Theoretically, a child produced by this process would inherit its nuclear DNA from its mother and father and healthy mitochondrial DNA from a donor egg. This procedure would not constitute reproductive cloning because the child's genetic makeup would be as unique as that of a child produced by conventional sexual means.

Nonreproductive cloning is legal in the United Kingdom. Since the early 1990s British scientists have been allowed to create human embryos for research purposes and perform experiments in therapeutic cloning. The Human Fertilization and Embryology Act of 1990 established a system for regulating the creation and use of embryos. Research leading to reproductive cloning is banned, but therapeutic cloning in order to generate healthy replacements for diseased tissues and organs is permitted. Some ethicists and religious leaders object to all experiments on embryos, while others argue that even therapeutic cloning should be banned because it would eventually lead to reproductive cloning. While human cloning and human stem cell research are actually technically distinct, these issues have become virtually inseparable because both involve the use of human embryos.

President George W. Bush, who opposes cloning humans for research and reproductive purposes, immediately announced support for the anti-cloning bill passed by the House. President Bush has taken the position that: "like a snowflake, each of these embryos is unique with the unique genetic potential of an individual human being." Further confusion and controversy was, therefore, sparked by Bush's decision to allow limited federal financing for stem cell research on 60 cell lines that had already been established. Despite recognition of the potential value of the research, the president ruled out any future flexibility in his stem cell policy. Thus, Bush's decision angered groups on both sides of the argument: those who hoped that stem cell research would help people with serious diseases and disabilities and those who believe that the fertilized egg should be accorded full human status.

Less than a month after President Bush announced his decision on embryonic stem cell research observers noted that the substance of public debate had shifted from whether such research was ethical to a debate about whether essential biomedical research could be conducted in the United States. Despite confusion about scientific and technical issues, there is widespread public awareness of predictions that human cloning and stem cell research could provide treatments and cures for many diseases, if scientists are allowed the freedom to pursue all promising pathways. If patients and their advocacy groups think that cures are being withheld because of political and religious forces, there is little doubt that the nature of the public debate will become increasingly hostile.

The debate about the scientific and technical uncertainties of human cloning will presumably be settled in the not-too-distant future through experimentation in countries that allow this type of research to proceed. The situation is likely to be quite different where ethical issues are concerned. Those at one extreme believe that the use of embryos for research purposes is morally unacceptable on the grounds that an embryo should be accorded full human status from the moment of its creation. In contrast, some people believe that early embryos should not be considered human begins with special moral rights. Others consider the embryo a potential human being, but argue that the rights of the early embryo should be weighed against the potential benefits arising from research. The British Human Fertilisation and Embryology Act attempted to maintain an ethical "middle ground." Indeed, British authorities suggested that cloning embryos by the cell nuclear replacement technique that produced Dolly might be considered a form of transitional methodology that could eventually provide insights into genetic mechanisms for reprogramming adult cells.

Although many Americans believe that stem cell research and therapeutic cloning are morally justifiable because they offer the promise of curing disease and alleviating human suffering, others are unequivocally opposed to all forms of experimentation involving human embryos. Despite the potential benefits of cloning and stem cell research, most scientists acknowledge that there are still many technical and scientific problems. However, even if the scientific issues are resolved, ethical, emotional, and political issues will probably continue to dominate debates about human cloning.

—LOIS N. MAGNER

Viewpoint: Yes, because of the potential physical dangers and the profound ethical dilemmas it poses, the cloning of human beings should be prohibited.

On July 31, 2001, the U.S. House of Representatives passed legislation to prohibit the cloning of human beings (Human Cloning Prohibition Act of 2001, H.R. 2505). As defined in the bill, "human cloning means human asexual reproduction, accomplished by introducing nuclear material from one or more human somatic cells into a fertilized or unfertilized oocyte whose nuclear material has been removed or inactivated so as to produce a living organism (at any stage of development) that is genetically virtually identical to an existing or previously existing human organism." The bill makes it a federal crime with stiff penalties, including a fine of up to $1 million and imprisonment up to 10 years to attempt to or participate in an attempt to perform human cloning as defined by the act.

With this step the United States is now poised to join the international community. Many nations have already adopted the prohibition against human cloning. International scientific bodies with oversight for medicine, research, and health as well as biotechnology industry interest groups mostly support the prohibition. But the matter is not yet settled. Before the measure can take effect, it faces a vote in the U.S. Senate and it needs the president's signature.

What reasons or fears prompted U.S. law-makers to take such strong measures? The sanctions in the act are more commonly associated with major felonies. Are there sufficient dangers to the nation and to its citizens to call for prohibition of a scientific technique whose applicability to humans seems as yet theoretical?

Since 1997, when Dolly the sheep, the first mammal ever derived from a cell (from the udder) of an adult mammal (sheep), was announced to the world, the possibility of human cloning has entered a new stage. After 276 unsuccessful attempts, the "cloned" embryo implanted in a ewe went through the normal gestation period and was born alive, surviving and healthy to the present. This was indeed a first and a major breakthrough. Since that event, the feat has been replicated in several types of livestock on different occasions. In 1998 mice were successfully cloned from adult cells. Humans bear certain genetic similarities to mice, and so often mice are the experimental model for what will be studied subsequently in humans. The technique of cloning by somatic cell nuclear transfer (SCNT) is steadily improving, suggesting a certain momentum.

The animal successes have inspired some groups and scientists to announce publicly their aim of embarking on the cloning of human beings through the same technique that gave us Dolly and the several other groups of mammals that followed.

Asexual Reproduction

The technique itself raises fundamental questions. SCNT, as noted in the definition of the Human Cloning Prohibition Act, involves taking a cell—many types of cells seem to work—from a full-grown animal and removing the nucleus, which contains the complete genetic makeup, or DNA, of the animal. The nuclear DNA is then inserted into a separate unfertilized but enucleated ovum harvested from an adult mammal, even a mammal of a different species. After special preparation in a nutrient medium to allow the cell to reprogram itself and a small trigger of electric current to start mitosis, the "cloned" blastocyst, now with the nuclear DNA of an adult somatic cell in each of the multiplying cells, is implanted in the womb of a "gestational" mother, previously treated and made ready to accept the pregnancy. If the process is successful, the resultant birth yields a new individual animal, genetically identical to the animal that donated the nucleus yet at the same time different from any other animal: the DNA in the nucleus of its cells does not come from the mating of two animals, in which each parent's DNA combines to create a new individual. Rather the DNA is from one animal only.

Sexual reproduction with its commingling of the genetic endowment of two individuals has demonstrated its existential value. Over hundreds of millions of years, nature has used the process to great advantage to perpetuate and vary species, to bring new beings and new species into existence throughout the plant and animal kingdoms, to ensure the continued and enhanced adaptation of living things to changing environments, and to preserve life itself. It is also the process that in our experience gives the "stamp of individuality," producing new members of a species with a novel genetic endowment and, not rarely, new individuals with traits that are remarkable and prized as well as unique.

The Status of a Clone

Perhaps a superior or functionally perfect breed of animal might offer special advantages—although a world of racing in which thousands of Secretariats challenged each other over and over might give oddsmakers and bettors nightmares. Then again, some rare or endangered species might be preserved. When we turn to humans, however, the technique raises many questions and challenges regarding our most important values and basic notions.

Intuitively, then, we ask, "What kind of human being would the individual be who has the nuclear DNA of another preexisting individual?" Would the "clone" be another individual human being or somehow not "truly" human? Is the "latest edition" of the cloned individual an individual in his or her own right? If he or she has the nuclear DNA from only one preexisting individual, if he or she was not the product of separate sperm and ovum, would such an individual fit the term "human," the way the rest of us do? What of the relationship to the individual supplying the DNA? How would we describe their relationship? Would the term "parent" fit the relationship? Could this clone of an individual ever be accepted by society? Or, much more profoundly, could the clone come to accept himself or herself as each one of us do: a unique and special person, with a nature and a future that is no one else's?

The ready response to questions like these is to recognize that the questions relate to imponderables. Of course, we wonder about them, but there is no evidence on which we can base an answer and no way of predicting the reactions of the clone or of society to the clone. We can only surmise that, just as now, if there were a world where clones existed, there would be tolerance and prejudice. Some individuals would display resilience and others would experience psychological challenges that test them sorely. People and the laws of society would adjust in time, just as we have for artificial insemination and in vitro fertilization. If anything, the imponderables ought to give us pause, to prompt us to think before taking any fateful steps to clone a human being. Yet are the imponderables grounds enough to restrict the freedom of inquiry our society endorses? What does prohibiting experiments in human cloning—in fact, making it a crime—do for our right to pursue knowledge? Ironically, is it not the imponderables that intrigue us? They exert a pull on our minds to seek answers to precisely those questions we are on the verge of forbidding. Is this bringing us back to the message of the story of the garden of Eden of the Book of Genesis in the Bible: is there knowledge we are forbidden to seek?

A Threat to Free Inquiry?

Is this a dilemma? A "catch-22"? Will prohibiting cloning of human beings cut us off from learning the answers to significant scientific information? Many argue that the research into the techniques of human cloning and the use of cloning technology are critical to advances that may lead to cures for many diseases. For example, the use of cloning may allow us to develop ways to culture replacement tissues and bodily fluids that can be used to treat individuals without the usual difficulties of HLA matching and tissue rejection. A somatic cell taken from a burn victim may be inserted into an oocyte and the process of cell division initiated to grow skin in tissue culture without the intent ever to create another human being. So too for bone marrow, so vital for treating forms of cancer and immune deficiency diseases. Nerve tissue can be developed in the same manner to be used to treat paralysis in accident or stroke victims without the problems of rejection of tissue and the complications of using immunosuppressive drugs.

It is not yet certain that such potential advances will actually occur. But it is questionable how feasible they will be in practical application. Obviously, at some early stage of life, even just after birth, somatic cells might be harvested and banked to be used if there was ever a therapeutic application for the individual whose cells would be preserved and reengineered in this way. But the system for accomplishing this is impractical. No matter where the somatic cells, however transformed and primed for therapeutic application, are stored, there are problems of availability at the point of need. Even more problematic is the management of a storage and centralized system of reference to manage the process. However, might the technology be used in an ad hoc way, case by case, to meet an individual patient's needs?

The prospect of cures like these is on the horizon. But they do not require human cloning by SCNT to accomplish. If the projections of scientists are correct, the techniques of embryonic and adult stem cell harvesting and transformation will yield a supply that can be universally available. It will not be necessary to clone an individual's own tissue via SCNT. SCNT is a more complicated process with many more foreseeable logistical and technical problems. The technology of stem cell development appears to present fewer problems and the prospect of more widespread uses and greater flexibility.

Potential Compassionate Applications

Perhaps these are reasons enough to deemphasize human cloning through SCNT. Even to abandon it. But the Human Cloning Prohibition Act of 2001 places an absolute ban on the procedure. Consequently, even humanitarian uses, out of compassion, are prohibited.

Advocates of human cloning through SCNT use the example of a couple whose child might be replaced through the use of SCNT. For example, a young child is so severely injured that recovery is impossible, and the child lingers a brief time before dying in a comatose state. A cell taken from the child could be inserted into the specially prepared ooctyte of the mother and implanted in her. In this way, the child could be replicated as a replacement. The parents would have regained their lost child. A moving scenario, no doubt, even melodramatic, although we are very far from knowing how this situation would turn out. For one thing, it seems much more natural to have another child. The replacement may serve only to generate ambivalent feelings, and the child will bear a heavy burden, perhaps not loved for the distinct and separate individual he or she is.

Secondly, the harvesting of the oocytes is not straightforward. It takes time because there is not likely to be a supply of these on hand from the same mother. Thirdly, as we have learned from animal cloning, the technique has a minimal success rate. Disappointment and failure are likely, and at best it is a prolonged process. In making the decision to attempt cloning the lost child, the parents are acting under the strain of profound grief. Their loss is keenly felt and their judgment affected by the tragic circumstances. The doctor or research team required to carry out the procedure would need to divert their attention and resources to this set of tasks. Unless the parents had enormous wealth so they could assemble their own team, the scenario is more in the realm of fiction than a realistic exercise. Nor should we expect scientific research to channel itself to meet the rare occurrences of replacing children lost through tragedy.

However, cutting off research on human cloning through the technique of SCNT can cost us valuable knowledge of important benefit in another area: the treatment of infertility. Thousands of couples in the United States are unable to bear children because their reproductive systems function poorly or not at all. Assisted reproductive technology (ART) has been developed to remedy the condition. Artificial insemination, in vitro fertilization, drugs to stimulate ovulation, techniques of micro sperm extraction and direct injection into an ovum, and other techniques have been introduced successfully to treat human infertility.

Human cloning by means of SCNT offers a new method, giving hope to the thousands whose fundamental reproductive rights are thwarted by defects that cannot be treated by these accepted methods. For example, when the male is unable to produce sperm and the couple does not wish to use artificial insemination by a donor, cloning by SCNT would be an alternative. The insertion of the male spouse's nuclear DNA into the enucleated ovum of his wife allows the couple to have a child in a way that closely approximates a natural process of reproduction: the nuclear DNA, the ovum with the mitochondrial DNA of the woman, the implantation and natural process of pregnancy. Prohibition of human cloning cuts off this avenue for individuals to exercise their fundamental reproductive rights. A variant of this technique, in which the ovum of another woman is substituted for the ovum of the mother with a mitochondrial DNA defect and the nuclear DNA extracted from the fertilized embryo of the couple is inserted into the donated ovum, has been used with some success. Therefore, doesn't this prohibition interfere not just with the pursuit of knowledge for its own sake, but also run counter to the fundamental reproductive rights of individuals?

The Ethics of Human Experimentation

The argument that prohibiting human cloning through SCNT interferes with freedom of inquiry or impedes gaining knowledge essential to treating conditions that interfere with fundamental human reproductive rights overlooks an important consideration. The quest for knowledge for its own sake or to benefit others is not unrestricted. Ethical rules and codes govern the kinds of experimentation allowed on humans. Harms are to be avoided; risks must be minimized. Worthy goals and hopes do not justify harmful procedures or those unlikely to produce reliable results. Good intentions or claims of widespread benefits do not automatically redeem procedures of uncertain outcome. In a phrase, the end does not justify the means. The rules and codes for experimentation on humans are precise. Those who propose to perform the experiments must provide evidence that the experiment can work; that any harms it may cause can be avoided or limited; that the expected outcomes are based on earlier work that allows an extrapolation to the proposed experiment, and that the experimental design is methodologically sound and well controlled.

It is not sufficient to cite lofty goals or pressing needs when experiments may entail costs of personal loss, distress, and harm to individuals—or even significant risks for these harms. Aircraft, vehicles, bridges, buildings, equipment are all designed with extra margins of safety and outfitted with safeguards as a fail safe to prevent harms. Experiments that involve humans must also meet rigorous standards, including review by experts and by nonscientists, to meet the so-called sniff test. No one contends that we know enough about SCNT as a technique in other mammalian species to try it out in humans. Livestock with specially prized traits, laboratory animals with unique characteristics, the endangered species whose existence is imperiled—if our cloning experiments fail or turn out to have unacceptable consequences, corrections are possible and unwanted outcomes can be disposed of. Society does not permit such liberties with human life. A breed of sheep or cattle that has unexpected flaws along with or instead of the sought after traits may still have other uses or can be euthanized and autopsied to understand the reasons for lack of success. These options do not exist with the cloning of human beings, and therefore the prohibition from even beginning the process is necessary until the highest standards of safety and effectiveness can be demonstrated.

The Risks of Cloning

Some advance the argument that human cloning may be premature at this time, but scientific progress might reach the point of removing or offsetting the risk. However, prohibiting human cloning closes off the opportunity to ever reach the point of eliminating the possibility of failure or reducing it to acceptable levels. Humanity would never have succeeded in reaching outer space or landing on the moon if the terms were elimination of all risk. More to the point, there would be none of the cures, the vaccines, or the interventions of modern medicine if the advances needed to be free of risk. Life is full of risks. The achievements of humans could never have been made if the terms were "risk free."

This argument has force. But like many apparently persuasive arguments in favor of proceeding with human cloning, it obscures a feature of all the human achievements on which progress has been built. Of course there were risks. Those who accepted the challenge knew the risks and voluntarily accepted them. Experimental human cloning is different. The subjects in the cloning experiments are not only the healthy volunteers, for whom, after all, the risk is over once a cell is removed, once the oocytes are harvested and the pregnancy complete. The subjects in cloning experiments are not high-minded adventurers, heroic explorers, dedicated scientists, not even the desperate terminally ill or grievously afflicted or those showing their altruism by joining researchers in the quest to relieve suffering through biomedical experimentation. We recognize and appreciate the contributions and sacrifices that individuals make when they choose with a mind and voice of their own. The risks of human cloning experimentation fall disproportionately on the clones. And we who make the decisions on their behalf must think from what would be their point of view. When flaws and failures turn up later, we cannot point to the most fundamental precept for human experimentation: the well-informed and voluntary agreement of the individual to accept the risks, even those not currently foreseeable, and the freedom to quit the experiment when, in the individual's sole judgment, the risks no longer seem acceptable. This is the universal standard for human experimentation in the world today.

Who Decides?

Human clones would of course have no opportunity to weigh the risks in advance. Moreover, the flaws or risks are now incorporated into their very existence. The inexorable outcome of the uncertainties or failures of the experiment determine their destiny. Hence there is no voluntary agreement to accept the risks as a price of coming into existence and no opting out in the event the burdens seem no longer acceptable.

It is true that no human gets to choose to be born or to whom or under what circumstances. We have no choice but to accept and make the most of the natural lottery of existence. This is part of what defines being human. For most individuals it is normal to honor and appreciate the choice our parents made for us in deciding to conceive and bring us into the world. The same rules and codes of human experimentation noted earlier recognize the special and pivotal role of parents whenever medical research calls for children to be the experimental subjects. Procedures are in place that reflect the universal assumption of law, policy, and common sense, that parents are best situated to make decisions in the best interests of their children. There are even provisions to have checks and balances, should the situation suggest the parent(s) may not be guided by normal parental instincts. In addition, by giving permission for experimentation on their children, parents are agreeing to accept the outcomes, even in the event that they are less than what was hoped for. Experiments always have a degree of uncertainty. Parents are free to withdraw their children from the research and children themselves may request that the experiment be terminated when they find they do not wish to continue.

Are There Reliable Safeguards?

Inherent in the human cloning process is the unavoidable shifting of the burden of choice unequally to the clone, who is to be involuntarily recruited into the experiment with no chance to withdraw or to be withdrawn. Once begun, the experiment has passed the point of no return. Ideally, perhaps, an improved, even a fully perfected human cloning process ought to incorporate safeguards to detect potential flaws. Some of these safeguards already exist. Preimplantation genetic diagnosis (PGD) is a technique already available to screen embryos in vitro for a number of genetic diseases. With the rapid growth of genetic technology, it is possible that one day most, if not all, genetic defects could be screened for and so no anomalies would occur in the clone. Many other intrauterine techniques can detect developmental flaws during pregnancy. Serious congenital defects and damage as well as inherited metabolic deficiencies can be detected at birth or shortly thereafter. These problems can be managed in accordance with accepted standards of medical practice.

But so little is known at this time about the way the genome—each individual's genetic endowment—works developmentally and functionally before and after birth that many deficiencies or disorders will only emerge after many years. Evidence indicates that cells may have inherent in them a defined limit of passages: some reports claim Dolly the sheep is revealing indications of a more rapid cellular aging. Success rates in animal cloning through SCNT are poor: most clones never reach or complete the gestation process, or they display major abnormalities during gestation or at birth. The DNA of each individual has a complement of cellular mechanisms or switches that act to replicate cells at mitosis and to repair the damages to microscopic and molecular structures and processes essential to health, development, and survival. Some evidence of genetic instability has been identified in mice clones and in cellular processes with cognate human processes. More subtle differences in development or gene expression might only emerge from latency after years or in reaction to environmental influences, too late to detect or intercept.

Some scientists have offered the view that many of the more subtle effects in genetic structures may owe themselves to the sort of "imprinting" that takes place in the normal fertilization process. At that point, meiosis II, initiated by the single sperm that triggers a succession of biochemical events, reaches completion. Shortly thereafter, the events of embryonic development occur with the formation of the zygote and the beginning of cell division into daughter cells, each having the complement of DNA representing a component of each parent and with one set of the pair of parental genes becoming deactivated. It is possible that subcellular events at this stage, currently not well described or identified, may play a decisive role in normal development.

Recent reports have emerged surrounding a process of SCNT in a variant of the model we have been discussing so far. Scientists and clinicians have succeeded in overcoming defects in the mitochondrial DNA of women by the process of substituting a healthy oocyte from a donor for the oocyte with the deficiency. The donated oocyte has the nucleus removed or deactivated. Then the nucleus of an embryo, created in vitro with the sperm of the father and the mother's ovum, is inserted in the donor's enucleated ovum. The reconstituted embryo is implanted in the uterus of the wife for normal gestation. However, a number of the embryos thus created revealed signs of chromosomal defects, related to sex differentiation and mental retardation (Turner's syndrome). More subtler forms of deficiencies could only be ruled out by the process of trial and error, an unacceptable method for human experimentation. Thus the possibility of human cloning cannot be demonstrated without a huge and, in large part, unacceptable cost, both personal and financial, to the individuals involved—be they parents, the offspring, or the rest of society. To advocate investment of public research funds or expect any public endorsement for the dim and distant prospect of, at best, a highly limited success with slight benefit and significant risks is not justifiable.

The Public Interest

Even so, the recent bill approved by the U.S. House of Representatives is not limited to use of public funds. It proscribes all efforts at human cloning by SCNT. This must surely intrude on an area of scientific inquiry and reproductive rights. Private funding and initiatives are banned. How can this be justified? The reason is clear: this is an area that lawmakers have seen as a matter of public policy and profound public interest. Over a decade ago, a federal law was passed, with no real controversy, prohibiting the sale and trafficking of human solid organs. It was determined that it was against public policy and not in the public interest to have individuals sell their organs, even if they as donor and the recipient would stand to benefit from what is a lifesaving procedure. The prospect of a commercialization of human organs was ruled to be against the public good. Although cloning of human beings under private auspices is very different, still the authority of the Congress and federal government to prohibit what is detrimental to the public interest is clear. Cloning of human beings is antithetical to the fundamental notions of what constitutes human conception. The rationale for prohibiting human cloning is that it entails outright commodification of human embryos derived from laboratory manipulations and puts society at risk for the untoward results of flawed and unethical experimentation on humans. It is not in the public interest to allow human cloning to go forward.

Proponents of human cloning rebut this view by arguing that it is based on the irrational fears of the so-called slippery slope argument. This argument uses the logic that without an absolute prohibition of some possible course of action, society will by degrees move down so far that precedent after precedent we will incrementally reach a point no one ever wanted or foresaw, and it will then be impossible to turn back, just as if one step on the icy slope makes the fall inevitable. The argument for prohibiting human cloning is not at all an instance of arguing based on slippery slope logic, however. It is not that the possibility of misuses of human cloning or abuses to create "novel human beings" or to replicate outstanding or favored types of human beings is what induces the prohibition. It is not just to rule out looming science fiction scenarios.

The prohibition of human cloning through the process of SCNT is based on a thorough understanding and appreciation of the methodology of scientific experimentation. The experimental method proceeds by a process of trial and error. A hypotheses is formed. Data are gathered that either support or fail to support the hypothesis. Based on better data and clearer objectives garnered through the first experiment, new hypotheses are developed and the steps repeated. The result is greater accuracy and precision in the hypothesis or improved data collection. Or it leads to abandonment of the hypothesis as fundamentally flawed and not worth pursuing. The prohibition of human cloning is a declaration that efforts to engineer human embryos or beings in this way is off-limits to the method of trial and error. In effect, it is the rejection of a fundamentally flawed hypothesis.

Conclusion

In experimentation on human beings, the basic principles of human society apply. There must be a reasonable likelihood of an unequivocal outcome, not some 1% to 3% limited success rate with failures and successes allowing incremental advances at intolerable cost. We can only proceed based on thorough preliminary research and sound scientific design, and at this point the evidence seems to be leading in a direction away from the attempt at human cloning. Harms are to be avoided and risks minimized. But it is not possible to foresee the harms or risks, and it is impossible to reverse them should we discover them later. There is no turning back if we are unsuccessful. There is no opportunity to quit the experiment if the subject so decides.

The test is not whether we should allow human cloning on the premise that useful information or some possible benefit may emerge. The test is to adhere to the standards for human experimentation that have been developed and refined over the past 50 years and codified in a succession of declarations, pronouncements, and laws by governmental and international bodies throughout the world. The burden of proof for meeting these standards falls on those who propose to clone human beings by SCNT.

—CHARLES MACKAY

Viewpoint: No, the cloning of human beings should not be prohibited because the potential for medical accidents or malfeasance is grossly overstated, and the ethical questions raised by detractors are not unique to cloning—indeed, ethical questions attend every scientific advancement.

Every generation confronts moral, ethical, legal, and political problems regarding the appropriate use of new technology and the limits of scientific research. Which is to say, every generation confronts the problems that attend to the new knowledge and understanding about our world that such technology and research affords. At the same time, however, societies continue to promote the advancement of the science and research that makes possible such new technologies and the societal advances they facilitate.

This essay attempts to demystify the cloning process and demonstrate how cloning, both in its reproductive and therapeutic capacities, provides much needed and sought after answers to otherwise intractable medical problems and conditions. As it turns out, the fears and ethical concerns regarding the cloning of humans (or even human embryos) that have moved many, including the U.S. Congress, to favor an absolute prohibition on human simply are unfounded. Indeed, many of the fears regarding cloning are not novel to human cloning; they are the same fears of the unknown that generally are raised more out of naive, knee-jerk reactions to new scientific procedures than well-thought-out, empirically supported assessments. On all fronts, the fears regarding human cloning can be allayed.

In light of the many benefits human cloning can provide, it would be foolish to prohibit by law the cloning of human beings or human embryos. This is not to say we should ignore the many ethical and legal issues, as well as other potential problems, that cloning humans may create, but rather, it simply is to recognize that human cloning per se is not the moral monstrosity that many are making it out to be.

There is, however, an overlap between the issues of human cloning and abortion, discussed in more detail later. Consequently, those who are morally opposed to abortion may also be morally opposed to human cloning, at least its therapeutic aspect. Many will continue to believe that human cloning is inherently morally unjustified, if not evil, for the same reasons they believe abortion is inherently immoral: both abortion and cloning of human embryos for medical research involves the destruction of (at least) potential life. Of course, whether human embryos are deserving of the same respect as a viable human fetus depends on personal definitions of what constitutes life and the scope of certain protections and this invariably is the point where moral intuitions clash.

Rather than attempting the futile enterprise of rearranging the moral intuitions of others, this essay explains first that cloning essentially is just another method of reproduction. Second, related to this first point, it demonstrates a common reoccurrence in the history of science and technology, namely, the presence of what could be called the "offensive factor," which tends to accompany new scientific and technological breakthroughs. Although initially the majority of people may view these breakthroughs with disdain, in time, that same majority comes to accept them.

New Technology and New Ideas: Overcoming the Offensive Factor

As with virtually any new scientific advancement, there are a range of opinions on the issue of human cloning, from those that are morally opposed to it on religious grounds (e.g., the Catholic church), to, somewhat ironically, those that are in favor of it also on religious grounds (e.g., the Raelians, a religious order begun in the early 1970s in France that claims 55,000 members throughout the world; in 1997 the Raelians founded Clonaid, a company that conducts human cloning experiments).

The majority view, however, appears to be strongly opposed to the idea of cloning humans. That is not surprising. Indeed, throughout history, we can find many examples where a society initially condemned, or even was repulsed, by a new scientific practice or idea, although it would later come to accept and even embrace it. The performance of autopsies, organ donation, and the use of robots in manufacturing are but a few examples. Indeed, in the early 1970s, when in vitro fertilization (IVF) began on human beings, many in society—including medical professionals—opposed it vehemently on moral and ethical grounds. A doctor involved in one of the first IVF procedures was so appalled by the procedure that he deliberately destroyed the fertilized embryo because he thought the process was against nature. Now, of course, IVF clinics are so commonplace that the birth of so-called test-tube babies no longer are newsworthy events, and few, if any, contemporary medical professionals claim that IVF procedures are immoral, unethical, or should be prohibited.

For a more current example, witness the Internet. Although the Internet has greatly improved the exchange of information and ideas, it also has facilitated cybercrime and other economic crimes, and it has made it easier for individuals to engage in such illicit activities, which pose extreme threats to the security of nations and the stability of global markets. Does the fact that even a single individual could cause widespread damage mean we should dismantle the entire Internet? Few would agree, and the billions that benefit from and rely on its existence would undoubtedly fight such efforts. Indeed, in today's interconnected world, dismantling the Internet probably would be impossible.

Thus when new technology and new ideas spring forth, it often is difficult, if not impossible, to prevent their propagation. The "new" generally has both aspects of the "good" as well as the "bad." But the bad should not necessarily deny us the benefits of the good. Therefore, rather than futilely attempting to prevent human cloning because of the evils that might spring from it, we should, as we have done with other new technologies and ideas, embrace it for the benefits and new knowledge that will emanate from it, all the while doing the best we can to minimize abuses. Otherwise, we risk driving the cloning of humans underground, and that could be a far worse evil.

To be sure, many moral, ethical, and legal issues must be addressed with respect to cloning humans, not the least of which concerns the possibility that cloning humans will open a market for "designer babies," which could lead to eugenics. Again, the potential for abuse always accompanies the advent of new technology. Although human cloning now may be perceived as something bizarre and foreign to us, within a generation—perhaps even earlier—cloning humans will be as noncontroversial as IVF, surrogate motherhood, and organ transplantation. So while we grow accustomed to the new technology and knowledge that human cloning may bring, there simply is no good reason why human cloning should be prohibited, but there are many reasons—discussed later—why research in the area should continue. And while research continues, we can work toward addressing the ethical issues regarding human cloning by developing professional codes of conduct and governmental regulation where necessary in order to minimize potential abuse, just as we did regarding organ transplantation and initial fears that organ transplantation would create black markets in organs. The problem, then, is not the technology per se, but how we use that technology.

What Is Human Cloning?

Perhaps the most significant impediment to new technology and ideas is that few people understand exactly what they are at first, and these misunderstandings breed fear and contempt. First and foremost, human cloning is not anything like photocopying oneself. For example, let's say Jackie A, a 30-year-old female, decides to clone herself. If she wants to "replicate" herself so there will be another 30-year-old female—we call this replicant Jackie B—that looks identical to her, Jackie A will be disappointed. Literally replicating oneself physically is impossible, and it is not what is meant by human cloning.

But Jackie A could do exactly what scientists in Scotland did with Dolly the sheep. Known as somatic cell nuclear transfer (SCNT), a doctor would first remove a mature but unfertilized egg from Jackie A or utilize one from a donor. The doctor then would remove the egg's nucleus, which only would have 23 chromosomes, half the necessary amount for human reproduction, and replace it with the nucleus of another cell—a somatic cell, which would have a full complement of 46 chromosomes. As we have assumed, if Jackie A wished to clone herself, the somatic cell simply would come from Jackie A. The egg with the new nucleus then would be chemically treated so it would behave as if it had been fertilized. Once the egg begins to divide, it then would be transferred into Jackie A's uterus, initiating pregnancy.

Essentially, except for the nuclear transfer, the procedure is identical to now common IVF procedures. If all goes well, within approximately nine months, Jackie A will give birth to a daughter—an infant daughter, to be sure—who is genetically identical to Jackie A. Thus Jackie A has "cloned" herself. Jackie A's daughter, whom we have named Jackie B, is not a "replicant," but a completely separate individual—she will not share any of Jackie B's memories or consciousness, just as a child does not share any such traits of its parents. Jackie B, however, will grow up to look nearly identical to Jackie A inasmuch as she shares all of Jackie A's genetic identity. The "odd" part is that not only is Jackie B the daughter of Jackie A, but Jackie B also is Jackie A's genetic twin sister.

Some people may find this result a bit unsettling inasmuch as it appears to be quite unusual or "unnatural"—how can someone be both a daughter and a sister to her mother? First, whether we refer to someone as a sister, mother, brother, or father often turns not on genetic or biological relationships but on other social conditions and relationships. Adopted children, for example, do not share any of the genetic features of their adoptive parents, yet they still are recognized as the children and heirs of their parents. We speak of adopted children's birth parents as opposed to their (adoptive) parents to make such a distinction.

Similarly, in light of the phenomenon of surrogate motherhood, merely because someone is born from a particular woman does not necessarily mean that same woman is even the individual's biological mother: a surrogate mother could simply be a woman who has agreed to carry the fertilized egg of another woman. As a result, in such situations the child born to the surrogate mother shares none of the surrogate mother's genetic material. Thus familial relations no longer are simply a matter of biology and genetics, but more a matter of social constructions.

Second, sometimes even in nature we can witness so-called unnatural results. If your mother, for example, is an identical twin, then her twin, of course, is your aunt. But, interestingly enough, she also is your genetic mother in the sense that genetically speaking, she is identical to your mother. In such a situation, your aunt—genetically speaking—both is your aunt and your mother. Of course, we do not really consider your aunt to also be your mother merely because she is genetically identical to your mother. That would be silly. Your mother is your mother by virtue of the fact that she bore and reared you (although, as we discussed earlier, giving birth to someone does not necessarily mean the child and mother are genetically related). Likewise, it would be absurd to seriously consider Jackie A's daughter to also be her sister merely because she is genetically identical to Jackie A.

Why Should We Clone at All?

As of this writing, it is unknown whether human cloning actually could be performed today. It also is unclear whether it already has occurred. What is evident, however, is that if human cloning is not technologically feasible now, it certainly is theoretically possible, and, once the procedures are refined, likely will occur soon. Indeed, in addition to the Raelians, Severino Antinori—a controversial fertility doctor from Italy—has announced publicly that he will be going forward with implanting cloned human embryos in volunteers shortly. Whether these experiments will be successful remains to be seen, but if they are, the first cloned human may be born in the summer of 2002.

In light of this (temporary) uncertainty with respect to the feasibility of successfully cloning a human, many opponents of human cloning argue in favor of a moratorium on human cloning. Such opponents point out that the process by which to clone mammals, let alone humans, is not yet perfected and could result in severely malformed and stillborn children. Certainly these are valid worries that cannot be ignored. Unfortunately, such worries cannot be resolved via a moratorium, for how can the necessary science advance if no research is being performed? Experimentation can be performed without impregnating human females of course. But just as there had to be a first heart transplant patient, there will have to be a first cloned embryo implanted into a woman if human cloning ever is to be achieved. There are always risks. The point of research is to minimize them, and a moratorium simply misses that point.

In any event, what follows with regard to human cloning assumes that the science will, if not now, eventually be perfected so these worries about malformations and stillbirths (both of which occur naturally anyway, lest we forget) can be greatly reduced. Assuming that human cloning will not present such dangers to either the child or the mother, there still remains the question of why we would want to clone humans at all.

Reproductive Cloning.

As already mentioned, human cloning essentially is a method for asexual reproduction. As such, it can allow infertile couples or even single persons to reproduce offspring that are biologically related to them. A husband who no longer is able to produce sperm nevertheless still could have a biological heir by implanting his DNA into the egg of his wife (or, if the couple so choose, a surrogate). Likewise, via human cloning, a single woman, a single man, or even same-sex couples would be able to reproduce biologically related heirs. Adoption always is an option for such persons, but for some, the desire for biologically related children is a more attractive option. Essentially, then, human cloning makes available the possibility of reproduction to those who otherwise would be unable to reproduce.

The imagination can run wild with the possibilities that cloning humans for reproductive purposes provides. For instance, a couple's child dies in a horrific accident and they no longer are able to conceive a child. They are devastated. Would it be unethical of them to clone the child? Certainly, if they believe the cloned child will be just like their deceased child. They should be disabused of their misconception. The cloned child will be a completely new person even though it will look just like the deceased child. The parents cannot bring their deceased child back to life. Even if they understand that, is there still a problem with them wanting another child to replace the one they have lost?

Similarly, assume the same couple has a child dying of a terminal disease in need of a bone marrow transplant. No donors can be found. Some couples have, in fact, conceived children for the purpose of actually creating a possible donor for their dying child (which creates ethical issues of its own). Unfortunately, the new child may not necessarily be a good match for the dying child. Thus would it be unethical for the couple instead to clone their dying child in order to use the marrow from the clone—who necessarily will be a perfect match—to save their dying child? In effect, in order to save the child's life, the couple simply would be reproducing their child's twin.

Finally, cloning raises the specter of eugenics, which many associate with Nazi Germany and those who promote beliefs in racial supremacy. With cloning, we could "breed" superior humans who are smarter. Certainly, so-called designer babies would be possible with cloning. If that bothers us, however, we could impose specific restrictions on the cloning of humans and create a regulatory and enforcement body to oversee such procedures, just like we have done with organ donation. And just as importantly, we can inform those who are interested in cloning themselves, or a relative, or a friend, about what cloning actually is and clear up any misconceptions they might have about the procedure. In short, it is possible to define appropriate and inappropriate uses for cloning just as we have for a variety of other new medical procedures. Merely because some might abuse cloning should not preclude others from otherwise benefiting from the cloning procedure.

Therapeutic Cloning.

Unlike reproductive cloning, therapeutic cloning does not involve reproduction, but the initial process is the same. A human embryo is cloned not to produce a child, but in order to retrieve its stem cells. Stem cells are unique in that they can be "grown" into virtually any type of cell in the body. According to some researchers, stem cell research may provide breakthroughs in the treatment of spinal cord injury and repair and a way to overcome the debilitating effects of many neurological disorders.

Because stem cells can be cultivated into the tissue of any organs, they also suggest a way for doctors to avoid the problems of organ transplantation. Often the patient's body receiving the organ rejects it. As a result, the patient must be given high doses of anti-rejection drugs. The same problems hold true for artificial organs. But anti-rejection drugs often have severe side effects. In addition to these problems, far more patients are in need of organs than are available. These patients often must wait for long periods of time, sometimes years, for an available organ and then hope the organ is not rejected by the body. Very often, such patients die just waiting for the organ.

Using stem cells to cultivate new organs would alleviate both these problems. First, because the organ simply would be cloned from the patient's DNA, the patient's body likely would not reject the organ for it essentially is the same organ from the perspective of the body. Second, there would be no waiting list for the patient. Whenever a new organ is needed, the patient's doctor would clone the needed organ from the patient.

So what possibly could be the problem with therapeutic cloning in light of these potential benefits? The retrieval of stem cells requires destroying the embryo. Note that stem cells can also be retrieved from adult cells, rather than embryos. However, whether such adult stem cells are as effective as embryonic stem cells still is an open question. Because of this, some religious groups are morally opposed to therapeutic cloning for the same reason they are morally opposed to abortion: they consider the embryo to be a human being (or, at least, with the potential for life), and therefore the destruction of the embryo is unjustified even if it will save the life of another.

Whether Americans consider an embryo to be a human being certainly is a matter of debate. According to an August 14, 2001, Gallup poll, only 36% of Americans believe that embryos deserve the same protection as human life. The same poll revealed that more than 70% of Americans think research on stem cells is necessary including, surprisingly, 31% who think that stem cell research is morally wrong. In light of this, it certainly appears that such moral objections do not dissuade most Americans from the importance of stem cell research. In contrast, a June 27, 2001, Gallup poll revealed that 89% of Americans are opposed to reproductive cloning. Evidently, therapeutic cloning is not as offensive as reproductive cloning.

Conclusion

Human cloning essentially is human reproduction—nothing more, nothing less. How it is performed and the results that may follow, however, are new. This is where the offensive factor mentioned earlier comes in. As with other new technologies and new ideas that have been fostered by scientific research, we need to (and hopefully will), get beyond the repugnance we feel about human cloning. Recently, the U.S. House of Representatives passed the Human Cloning Prohibition Act of 2001 (H.R. 2505), and this legislation currently is being considered by the Senate. The act will make the cloning of human embryos a crime punishable by up to 10 years in prison and a civil penalty of at least $1 million.

Whether such legislation will become law is uncertain as of this writing, but undeniably the genie is out of the bottle—the technology already exists. Such legislation, most likely enacted out of political expediency in the face of the offensive factor, likely will do little to prevent determined researchers and advocates of human cloning from going forward with experimentation abroad.

Given that religious views often govern and guide our feelings toward such new technologies and new ideas, we return to the events surrounding what arguably was the first instance of cloning: God's creation of Eve from a rib of Adam. After their creation, both Adam and Eve were instructed by God not to eat the fruit of the Tree of Knowledge on pain of death. Tempted by a serpent, however, Eve disobeyed God by eating the fruit and offered it to Adam. By eating the fruit, both Adam and Eve suddenly became aware of their surroundings; they had acquired new knowledge. Afraid they would soon eat the fruit of the Tree of Life and thereby become immortal, God quickly banished them from the Garden of Eden "lest they become like one of Us."

Traditionally, the tale of Adam and Eve is thought to represent the first instance of sin, the "original sin," and the consequences that flowed from that sin. But there is another way to interpret their story. The serpent, after all, tempted Eve by informing her that should she eat of the Tree of Knowledge her eyes would be opened, and she would come to know right from wrong. In essence, it was this fact—a craving for new knowledge—that moved Eve to disobey God's command and risk death.

Although many take the moral of the story to concern the ramifications of disobeying the command of God, we also can see that it represents the ramifications of new knowledge. Eve, who essentially was the first scientist, sought out new knowledge, and like some of the millions of scientists who have followed her, also suffered some severe consequences. Thus new knowledge always comes at a price, but what is the alternative? Human cloning should not be prohibited because of the new knowledge it affords—its abuse, of course, should be.

—MARK H. ALLENBAUGH

Further Reading

Andrews, Lori. The Clone Age: Adventures in the New World of Reproductive Technology. New York: Henry Holt, 2000.

Annas, George, and Michael Godein, eds. The Nazi Doctors and the Nuremberg Code: Human Rights in Human Experimentation. New York: Oxford University Press, 1992.

Human Cloning Prohibition Act of 2001. 107th Cong., 1st sess., H.R. 2505.

Jaenisch, Rudolf, and Ian Wilmut. "Don't Clone Humans!" Science 291 (March 2001): 2552.

Kass, Leon. "Preventing a Brave New World," The New Republic, May 21, 2001, p. 36.

——, and James Q. Wilson. The Ethics of Human Cloning. Washington, D.C.: American Enterprise Institute, 1998.

Kolata, Gina. Clone: The Road to Dolly, and the Path Ahead. New York: William Morrow, 1997.

National Bioethics Advisory Commission, Cloning Human Beings: Report and Recommendations. Rockville, Md.: June 1997. Also available at <http://bioethics.gov/pubs/cloning/>.

Silver, Lee. Remaking Eden: Cloning and Beyond in a Brave New World. New York: Avon, 1997.

——. Remaking Eden: How Genetic Engineering and Cloning Will Transform the American Family. New York: Avon, 1998. U.S. House. Report on Human Cloning Prohibition Act of 2001, H.R. Rep. No. 107-170, 2001.

KEY TERMS

BLASTOCYST:

Developing preimplantation embryo, consisting of a sphere of cells made up of outer support cells, a fluid-filled cavity, and an inner cell mass.

CHROMOSOME:

Composed chiefly of DNA, the carrier of hereditary information, these structures are contained in the nucleus of the cell. Normal human chromosomes contain 46 chromosomes, one half from each parent.

DNA:

Deoxyribonucleic acid; found primarily in the nucleus of the cell. It carries all the instructions for making the structures and materials necessary for bodily functions.

ENUCLEATED OVUM:

Ovum from which the nucleus has been removed.

FERTILIZATION:

Process by which sperm enters the ovum and initiates the process that ends with the formation of the zygote.

GENE:

Working subunit of DNA that carries the instructions for making a specific product essential to bodily functioning.

GENETIC IMPRINTING:

Process that determines which one of a pair of genes (mother's and father's) will be active in an individual.

GENOME:

Complete genetic makeup of a cell or organism.

IN VITRO FERTILIZATION:

Assisted reproduction technique in which fertilization occurs outside the body.

MEIOSIS:

Special type of cell division occurring in the germ cells by which each germ cell contains half the chromosomes of the parent cell. In humans this is 23 chromosomes.

MITOCHONDRION:

Cellular organelle that provides enrgy to the cell and contains maternal DNA.

MITOSIS:

Process of ordinary cell division, resulting in the formation of two cells identical genetically and identical to the parent cell.

NUCLEUS:

Cell structure that contains the chromosomes.

OOCYTE:

Mature female germ cell or egg.

SPERM:

Mature male reproductive cells.

ZYGOTE:

The single-celled fertilized egg.

IMPRINTING AND THE DISCOVERY OF IGF2R

On August 7, 2001, the United States National Academy of Sciences convened a panel of international experts in the scientific, medical, legal, and ethical aspects of human cloning. The debate centered on the potential hazards and current limitations of the cloning process in animals. Scientific and medical opinion weighed in heavily against the prospect of human cloning. Not enough was understood about the cloning process in animals to employ the current technology to clone humans. Scientists cited the inherent difficulties of inducing safe and successful gestation in animals as evidence of the high odds against achieving success in humans. The effects of culture media on embryos cloned by somatic cell nuclear transfer (SCNT) had not yet been examined enough to permit detection of possible flaws traceable to contamination by the nutrients in which the clones are maintained or to rule out cross-species pathogens. Other data pointed to possible interactions of the culture medium with the cloned embryo, which might trigger anomalies in the critical processes of gene expression, resulting in developmental failures or abnormalities.

More concrete parallels with problems encountered in animal cloning suggested that a technical barrier might exist as well. If so, the fundamental feasibility of human cloning was in question. Sexual reproduction involves a step called "imprinting." In this step one set of the pair of complementary genes from each parent becomes deactivated. The corresponding genes from the other parent ensure that the development and functions determined by the gene remain active. Because SCNT is asexual reproduction, the "imprinting" process does not occur. In the transferred genome critical parts of the genome are permanently deactivated. Consequently, genes critical to successful gestation and embryonic development do not function. If this proves to be the case, then we are up against an insurmountable barrier to human cloning.

On August 15, 2001, scientists startled the world with a new finding: humans and other primates receive two functioning copies of genes. In an article published in Human Molecular Genetics, scientists J. Keith Killian and Randy Jirtle and their collaborators identified a key gene called insulin-like growth factor II receptor (IGF2R) which they had traced in mammalian evolution. Sometime about 70 million years ago, the ancestors of primates evolved to possess two functional copies of this gene. The IGF2R gene is critical to normal fetal development. The absence of a working copy in the livestock and murine models used in cloning accounts for the failures, according to the scientists who published the article. Dr. Killian stated, "This is the first concrete genetic data showing that the cloning process could be less complicated in humans than in sheep." It is too soon to know whether other factors in the human genome also contribute to, or hinder, the technical possibility of cloning humans. But this key finding settles one question about the phenomenon of genomic "imprinting."

—Charles R. MacKay

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