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Cloning burst upon the scene in February, 1997, with the announcement of the birth of Dolly, the cloned sheep. She was created when researchers took the DNA nucleus from a cell of an adult sheep and fused it with an egg from another sheep. Shortly after Dolly was born, mice, cattle, goats, pigs, and cats were also cloned.

For biologists, however, the word cloning refers not to producing new animals but rather to copying DNA, including short segments such as genes or parts of genes. This ability to copy DNA is a basic technique of genetic engineering used in almost every form of research and biotechnology. In Dolly, copying was taken to the ultimate scale, the copying of the entire nucleus or the entire genome of the sheep. The transfer of the nucleus is usually called somatic cell nuclear transfer (SCNT), and this is what most people have in mind when they speak of cloning.

Dolly's birth immediately raised the question of human cloning. In principle, a human baby could be made using SCNT. The technical obstacles are, however, greater than most people recognize. Experts in the field doubt that human reproductive cloning can be safely pursued, at least for several decades. In Dolly's case, it took 277 attempts to create one live and apparently healthy sheep, a risk level that is clearly unacceptable for human reproduction. More important, the state of Dolly's health is not fully known. One fear associated with cloning is that the clone, having nuclear DNA that may be many years old, will age prematurely, at least in some respects. Mammalian procreation is a profoundly complicated process, as yet little understood, with subtlety of communication between sperm, egg, and chromosomes, which allows DNA from adults to turn back its clock and become, all over again, the DNA of a newly fertilized egg, an embryo, a fetus, and so forth through a complex developmental process. Using cloning to produce a healthy human baby who will become a healthy adult is decidedly beyond the ability of science as of 2002. Expert panels of scientists all strongly condemn the use of SCNT to produce a human baby.

Therapeutic cloning

Cloning, however, may have other human applications beside reproduction, and many scientists endorse these. Usually such applications are referred to as therapeutic cloning, but it should be noted that much research must occur before any therapy can be achieved. Especially interesting is the possibility of combining nonreproductive cloning with embryonic stem cell technologies. Human embryonic stem cells, first isolated in 1998, appear promising as a source of cells that can be used to help the human body regenerate itself. Based on research performed in mice and rats, scientists are optimistic that stem cells may someday be implanted in human beings to regenerate cells or tissues, perhaps anywhere in the body, possibly to treat many conditions, ranging from diseases such as Parkinson's to tissue damage from heart attack.

Embryonic stem cells are derived from embryos, which are destroyed in the process. Some scientists are hopeful that they will be able to find stem cells in the patient's own body that they can isolate and culture, then return to the body as regenerative therapy. Others think that stem cells from embryos are the most promising for therapy. But if implanted in a patient, embryonic stem cells would probably be rejected by the patient's immune system. One way to avoid such rejection, some believe, is to use SCNT. An embryo would be created for the patient using the patient's own DNA. After a few days, the embryo would be destroyed. The stem cells taken from the embryo would be cultured and put into the patient's body, where they might take up the function of damaged cells and be integrated into the body without immune response.

Religious concerns about cloning

While many believe the potential benefits justify research in therapeutic cloning, some object on religious grounds. Many Roman Catholic and Orthodox Christians reject this whole line of research because it uses embryos as instruments of healing for another's benefit rather than respecting them as human lives in their own right. Others believe that if nonreproductive cloning is permitted, even to treat desperately ill patients, then it will become impossible to prevent reproductive cloning, and so they want to hold the line against all human uses of SCNT. A few Protestant and Jewish groups and scholars have given limited approval to nonreproductive cloning.

Outside the United States, most countries with research in this area reject reproductive cloning but permit cloning for research and therapy. In the United States, federal funding is not available as of 2002 for any research involving human embryos. Privately funded research, however, faces no legal limits, even for reproductive cloning. In 2001, one U.S. corporate laboratory, Advanced Cell Technology, published its work, largely unsuccessful, to create human cloned embryos in order to extract stem cells. Some religious leaders object to this situation in which privately funded research is left unregulated.

When it comes to reproductive cloning, religious voices are nearly all agreed in their opposition, although they may give different reasons. Aside from a few isolated individuals, no one has offered a religious argument in support of reproductive cloning. All religious voices agree with the majority of scientists in their objection to cloning based on the medical risk that it might pose for the cloned person, who, even if born healthy, may experience developmental problems, including neurological difficulties, later in life. Until it is known that these risks are not significantly higher for the clone than for someone otherwise conceived, most scientists and ethicists agree that researchers have no right to attempt cloning.

Some religious scholars and organizations oppose cloning as incompatible with social justice. As an exotic form of medicine that benefits the rich, cloning should be opposed in favor of more basic health care and universal access to it.

Others oppose reproductive cloning because it goes against the nature of sexual reproduction, which has profound benefits for a species. Human beings are sexual beings, it is argued, and the necessity of sex for procreation is grounded in hundreds of millions of years of evolution and should not be lightly cast aside by technological innovation. Transcending the biological advantage of sexual procreation, some argue, are the moral and spiritual advantages of the unity of male and female in love, from which a new life emerges from the openness of being, far more than from the designs of will.

Some believe that cloning would confuse and probably subvert relationships between parents and their cloned children. If one person in a couple were the source of the clone's DNA, at a genetic level that parent would be a twin of the clone, not a parent. Whether biological confusion would amount to psychological or moral disorder is of course debatable, but any test might result in tragic consequences. Furthermore, cloning creates a child with nuclear DNA that, in some way at least, is already known. This nuclear DNA begins a new life, not with the usual uncertainties of sexual recombination but through the controls of technology. Many have said that the power to create a clone gives parents far too much power to define their children's genetic identity. Unlike standard reproductive medicine, even if combined in the future with technologies of genetic modification, cloning allows parents to specify that their child will have exactly the nuclear DNA found in the clone's original. This is assuredly not to say that parents may thereby select or control their child's personality or abilities, because persons are more than genes. But some fear that by its nature cloning moves too far in the direction of control and away from the unpredictability of ordinary procreation, so far in fact that a normal parent-child relationship cannot emerge in its proper course. To move in that direction at all is to risk subverting the virtues of parenting, such as unqualified acceptance.

Finally, some have held that cloning will place an unacceptable burden on the cloned child to fulfill the expectations that motivated their cloning in the first place. The fact that the parents may have some prior knowledge of how the clone's nuclear DNA was lived by the clone's original will lead the clone to think that the parents want a child with just these traits. One can imagine that clones will believe they are accepted and loved because they fulfill expectations and not because of their own unique and surprising identity.

In time, reproductive cloning may be widely accepted, much as in vitro fertilization has become accepted. But within religious communities, opposition to cloning is so strong that it is hard to imagine that religious people will ever accept it as a morally appropriate means of human procreation. Nevertheless, despite the strength of the objections, many recognize that human reproductive cloning will occur in time, and when it does the religious concern will shift from preventing cloning to affirming the full human dignity of the clone.

See also ANIMAL RIGHTS; BIOTECHNOLOGY; DNA; GENETIC ENGINEERING; REPRODUCTIVE TECHNOLOGY; STEM CELL RESEARCH

RONALD COLE-TURNER