Reproductive Cloning

A clone can be thought of as an individual or as a group of individuals who are genetically identical. Identical twins are such clones. Since the birth of Dolly the sheep at the Roslin Institute near Edinburgh, Scotland, in March 1996, people have wondered whether it also would be possible to produce humans by cloning. Dolly was a clone, a genetic "copy," of a six-year-old ewe. She was cre­ated by inserting the nucleus of a cell from the udder of this ewe into a sheep egg from which the nucleus had been removed. After being stimulated to grow, the egg was implanted into the uterus of another sheep from which Dolly was born. Because Dolly was a mammal like us, people con­cluded that it might be possible to clone human

beings as well. Moreover, Dolly was produced from a body or somatic cell of an adult sheep with already determined characteristics. Because the cells of an adult are already differentiated—that is, they have taken on specialized roles—scientists had previously assumed that cloning from such cells would not be possible. Now, it seemed, pro­ducing an identical, although younger, twin of an already existing human being might be possible.

The type of cloning described above is called somatic cell nuclear transfer (SCNT) because it transfers the nucleus of a somatic or bodily cell into an egg whose own nucleus has been removed. Cloning can also be done through a fission process, or cutting of an early embryo. Through this method it may be possible to make identical human twins or triplets from one embryo.

The potential for human cloning can be surmised from the progress of animal cloning. In just the past two decades, many higher mammals have been produced through cloning, including cows, sheep, goats, mice, pigs, rabbits, and a cat named "CC" for "carbon copy or "copy cat'." CC was produced in a project funded by an Arizona millionaire, John Sperling, who wanted to clone his pet dog, Missy, who had died. The company he and his team of sci­entists established, Genetic Savings and Clone, was based in Sausalito, California, and Texas A&M University at College Station, Texas.¹⁶ In 2004, it was charging $50,000 for a cloned cat and $295 to $1,395 to store genetic material from a cat. Two kit­tens, Tabouli and Baba Ganoush, who were cloned from the same female Bengal tiger cat, were dis­played at the annual cat show at Madison Square Garden in October 2004. According to the owners, the kittens have personality similarities as well as differences. In late 2004, the company also expected to deliver five more cloned kittens.'⁷ Cloned ani­mals have themselves produced offspring in the natural way. Dolly had six seemingly normal lambs. Several generations of mice have also been pro­duced through SCNT. Clones have been derived not only from udder cells but also from cells from embryos and fetuses, as well as from mice tails and cumulus cells.

On February 25, 2005, a cloned foal stallion of a prize race horse was born in Cremona, Italy. The

410 PART TWO ■ ETHICAL ISSUES

owners reported that the foal would be used pri­marily for breeding and, as of 2007, he appeared to be well and ready for that purpose.¹⁸ In 2006, Genetic Savings and Clone closed its doors, going out of business. The owners found after all that their enterprise was not commercially viable.¹⁹

However, animal cloning has not always been efficient or safe. In the case of Dolly, for example, 277 eggs were used but only one was lamb pro­duced. Moreover, cloned animals also have exhib­ited various abnormalities. In one study, all twelve cloned mice died between one and two years of age. Six of the cloned mice had pneumonia, four had serious liver damage, and one had leukemia and lung cancer. Dolly may have had arthritis, although this has been disputed. Some theorists suggest that this may be because she was cloned from the cell of an already aged adult sheep. In February 2003, Dolly was euthanized because she had developed an infectious and terminal lung dis­ease. (However, see the discussion of this in the reading in this chapter by Macintosh.)

In terms of human reproduction, cloning would be directed to the development of a new human being who would be the identical twin of the person whose cell was used in the process. On the one hand, reproductive cloning may be thought of as one of several reproductive technologies that have been developed in recent decades. Among these are artificial insemination, in vitro fertiliza­tion with its resulting "test-tube babies," donated and frozen embryos and eggs, and the use of sur­rogate mothers.

Although these other methods of reproduction have been widely accepted, there is almost univer­sal objection to reproductive cloning, even among those countries that allow and support stem cell research or therapeutic cloning. Some countries, such as the United Kingdom, have laws prohibiting reproductive cloning while still actively supporting therapeutic cloning. Japan, China, Singapore, and South Korea have similar laws. However, Germany, Austria, France, and the Netherlands have banned both types of cloning. Countries in South America, the Middle East, and Africa also have a diversity of regulation. In the United States, bills to regulate or prohibit human cloning have been proposed, but

none has yet passed both houses of Congress. One reason is the failure to agree on whether to make a distinction between the two types of cloning. Ethical questions are central to reproductive cloning, and thus our focus here is on that form.

Дата добавления: 2015-08-05