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EMBRYO CLONING  OF HUMANS:

(a.k.a. ARTIFICIAL TWINNING)

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Sponsored link.


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Embryo cloning topics covered in this essay:

bulletWhat it is
bulletHow it would be done
bulletHistory
bulletIs it ethical?
bulletReferences

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What is embryo cloning?

Cloning is the production of one or more individual plants or animals that are genetically identical to another plant or animal. 

Embryo cloning might be more accurately called "artificial twinning", because it simulates the mechanism by which twins naturally develop. It involves removing one or more cells from an embryo and encouraging the cell to develop into a separate embryo with the same DNA as the original. It has been successfully carried out for years on many species of animals. Some very limited experimentation has been done on human embryos. 

Nature itself is the greatest cloning agent. In about one of every 75 human conceptions, the fertilized ovum splits for some unknown reason and produces monozygotic (identical) twins. Each has an genetic makeup identical to the other. In cloning, this same operation is done intentionally in a laboratory. 

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How human embryo cloning would be done

Human embryo cloning starts with a standard in vitro fertilization procedure. Sperm and an egg cell are mixed together on a glass dish. After conception, the zygote (fertilized egg) is allowed to develop into a blastula (a hollow mass of cells). The zygote divides first into two cells, then four, then eight... A chemical is added to the dish to remove the "zona pellucida" covering. This material provides nutrients to the cells to promote cell division. With the covering removed, the blastula is divided into individual cells which are deposited on individual dishes. They are then coated with an artificial zona pellucida and allowed to divide and develop. The experiment by Sillman et al. showed that the best results could be obtained by interrupting the zygote at the two cell stage. Many of these pairs of zygotes were each able to develop to the 32 cell stage, but stalled at that point. They might well have had the potential to develop further and even mature into a viable fetus, except that the original ovum was defective and would have died anyway. For ethical reasons, the researchers had selected embryos which had no possibility of ever maturing into fetuses, and thus becoming newborn babies.

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History of embryo cloning:

Cloning of embryos has been used in mice experiments since the late 1970's, and in animal breeding since the late 1980's. The procedure splits a single fertilized ovum into two or more clones, each of which is then implanted into the womb of a receptive female.

However, research into cloning of human embryos has been restricted in the United States and in some other countries. Pro-life groups which oppose free access to abortion have had considerable political power. They were able to have all human embryo research banned by the Regan and Bush Presidencies during most of the 1980's and into the early 1990's. During the first few days of President Clinton's presidency, the ban on public funding of human embryo and fetal research was lifted.

We may not know the individual or team who first performed cloning of human embryos. The methods used have been understood for many years and actually used to clone embryos in cattle and sheep. It is likely that someone had successfully used the method on a human embryo in secret. The first publicly announced human cloning was done by Robert J. Stillman and his team at the George Washington Medical Center in Washington D.C. They took 17 genetically flawed human embryos which would have died within days no matter how they were treated. They were derived from an ovum that had been fertilized by two sperm. This resulted in an extra set of chromosomes which doomed the ovum's future. None could have developed into a fetus. These ovum were successfully split in 1994-OCT, each producing one or more clones. The main motive of the experiment seems to have been to trigger public debate on the ethics of human cloning.

Dr. Steven Muller headed a panel in the US whose mandate was to produce preliminary cloning guidelines. These would be used by the Federal National Institutes of Health to decide which cloning research to fund. The panel recommended that studies be normally limited to the use of preexisting, spare embryos - those that developed during in vitro fertilization procedures that had been performed to assist couples in conceiving. Generally about 20 or 24 ova are fertilized during these procedures. Only three or four are implanted in the woman. The extra zygotes are either discarded or frozen for possible future use. New embryos would only be prepared and used if needed for "compelling research." They further recommended that any studies be normally terminated within 14 days of conception. Some experiments might be authorized to continue until the 18th day, but no further. At that gestational age, neural tube closure begins; this is the start of the development of a nervous system. They recommended that certain procedures be banned, including implanting human embryos in other species, implanting cloned embryos into humans, the transfer of a nucleus from one embryo to another, and the use of embryos for sex selection.

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Is embryo cloning moral?

Cloning of animals seems to have a number of potentially positive results:

bulletScientists are attempting to create transgenic pigs which have human genes. Their heart, liver or kidneys might be useable as organ transplants in humans. This would save many lives; thousands of people die each year waiting for available human organs. Once achieved, transgenic animals could be cloned to produce as many organs as are needed.
bulletExperience gained in cloning may add to our understanding of genetics.
bulletResearchers have produced transgenic animals. These are genetically altered, typically in order to produce human hormones or proteins in its milk. These materials can be separated from the milk and used to heal humans. Cloning would produce as many genetically altered animals as are needed. The alternative is to simply allow them to mate; this would produce many offspring that had lost the inserted human gene and thus would be unable to produce the medication.

Embryo cloning of humans: Some scientists believe that embryo cloning and related research is moral and might eventually lead to very positive results:

bulletIt might produce greater understanding of the causes of miscarriages; this might lead to a treatment to prevent spontaneous abortions. This would be of immense help for women who cannot bring a fetus to term.
bulletIt might lead to an understanding of the mechanisms by which a morula (a mass of cells that has developed from a blastula) attaches itself to the wall of the uterus. This might generate new, effective contraceptives that exhibit very few side effects.
bulletThe rapid growth of the human morula is similar to the rate at which cancer cells propagate. Cancer researchers believe that if a method is found to stop the division of a human ovum then a technique for terminating the growth of a cancer might be found.
bulletParents who are known to be at risk of passing a genetic defect to a child could make use of cloning. A fertilized ovum could be cloned, and the duplicate tested for the disease or disorder. If the clone was free of genetic defects, then the other clone would be as well. The latter could be implanted in the woman and allowed to mature to term.
bulletIn conventional in vitro fertilization, doctors attempt to start with many ova, fertilize each with sperm and implant all of them in the woman's womb in the hope that one will result in pregnancy. But some women can only supply a single egg; her chances of becoming pregnant are slim. Through the use of embryo cloning, that egg might be divisible into, say, 8 zygotes for implanting. The chance of those women becoming pregnant would be much greater.
bulletCloning could produce a reservoir of "spare parts". Fertilized ova could be cloned into multiple zygotes; one could be implanted in the woman and allowed to develop into a normal baby; the other zygotes could be frozen for future use. In the event that the child required a bone marrow transplant, one of the zygotes could be taken out of storage, implanted, allowed to mature to a baby and then contribute some of its spare bone marrow to its (earlier) identical twin. Bone marrow can be harvested from a person without injuring them.
bulletA woman could prefer to have one set of identical twins, rather than go through two separate pregnancies. She might prefer this for a number of reasons:
bulletto minimize disruption to her career.
bulletto make a normal vaginal delivery possible (twin fetuses are smaller than a single fetus; delivery of a larger, single fetus might be impossible because of her shape.
bulletshe might prefer to only have to endure the discomfort of a single pregnancy.
bulletshe might wish to have children that could contribute a kidney to their sibling, if needed.

Through embryo cloning, she could be assured that she would deliver identical twins.

Some individuals and groups have expressed concerns about adverse effects of embryo cloning in humans, and question its morality:

bulletThe genetic screening test described above could also be used to eliminate zygotes of a particular gender, without requiring a later abortion.
bulletWhen the gene or genes that determine sexual orientation are located, cloning could also be used to eliminate zygotes of a particular sexual orientation.
bulletA country might finance a program similar to that of Nazi Germany whereby humans were bred to maximize certain traits. Once the "perfect human" was developed, embryo cloning could be used to replicate that individual and conceivably produce unlimited numbers of clones. The same approach could be used to create a genetic underclass for exploitation: e.g. individuals with sub-normal intelligence and above normal strength.
bulletThere is always the possibility of injuring or killing embryos. Most pro-life supporters believe that an embryo is a human person. During embryo cloning, they would be subjected to assault with the possibility of being murdered. The embryos would be treated as a commodity to be exploited, not as a person.

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References:

  1. Dr. B. Benoit maintains a Web page "HUMAN CLONING AND RE-ENGINEERING" that is dedicated to "the dissemination of information on human embryo cloning research and related topics, with special attention dirrected [sic] to the moral implications." See: http://cac.psu.edu/~gsg109/qs/emclone.html

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Copyright 1997 to 2001 incl. by Ontario Consultants on Religious Tolerance
Originally published: 1997-AUG-5
Extracted from the cloning menu on 2001-MAR-20

Last updated 2001-AUG-17
Author: B.A. Robinson

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