by Ben Best
The February 27, 1997 issue of NATURE [NATURE 385:810-813] contains a ground-breaking paper announcing the first successful cloning of a mammal from an adult cell. Dr. Ian Wilmut of Edinburgh, Scotland forced isolated adult sheep cells into a quiescent state by days of nutrient deprivation. Without nutrient, many genes become inactive and the cells revert to the dormant G0 or G1 stages of the cell cycle. The quiescent cells were fused with enucleated oocytes (egg cells). The resulting "zygotes" were allowed to grow into embryos and then transplanted into a surrogate-mother sheep. Literally speaking, these "zygotes" are not full clones when the recipient oocyte is not from the same individual because the mitochondrial DNA is that of another sheep. (For an elementary explanation of the technology of cloning, see The Cloning of Dolly.) By the end of the year 2000, eight mammalian species had been cloned, including mice, cows, sheep, goat, pigs and rats.
World reaction to this breakthrough was mostly a din of anti-scientific hysteria raised by the spectre of possible human cloning. Jeremy Rifkin declared human cloning to be a crime which should be punished "on a par with rape, child abuse and murder." A horde of religious spokespersons warned that humans have "neither the right nor the knowledge to play God". The same cry had been uttered in 1965 after the announcement of the first heart transplant. This argument can be (and often has been) made against every scientific advance. But the argument "if God had meant us to fly he would have given us wings" can easily be augmented with "or a brain to build airplanes". There is certainly no biblical scripture which forbids airplanes, heart transplants or cloning. An October 2002 US opinion poll found that 25% of males approved of cloning humans, but only 10% of females approved [SCIENCE 299:41 (2003)].
Although 277 adult cells were fused with ova, only 13 pregnancies and one live birth resulted. The primary donor cell culture came from the mammary gland of a 6-year-old pregnant sheep. The tissue was 90% epithelial cells, with the rest consisting of fibroblasts, myoepithelial cells and perhaps some relatively undifferentiated stem cells. The cell type (phenotype) of the successful donor cell is unknown. (The fact that the donor cell came from a breast inspired a wag to name the offspring "Dolly" in honor of a well-endowed celebrity of the same name.)
This project was backed by PPL Therapeutics P.L.C., which creates transgenic sheep&cows that produce milk containing human protein that can be used to feed human babies. Rather than go through the tedious&expensive process of creating each transgenic animal individually, the company seeks to produce a flock of cloned transgenic sheep which can then be breeded normally, while still producing the human milk protein. PPL is also working on cloning genetically engineered pigs for animal-to-human organ transplants.
Personally, I have long thought that it would be an excellent idea to improve the quality of the human race — and I have not believed that eugenics necessarily leads to genocide. Nonetheless, I didn't like the idea of entrusting government to conduct a eugenics program. Currently, I think the idea of eugenics is obsolete because science is so quickly approaching the capacity of improving the genetic makeup of individuals. Ironically, many of the anti-eugenicists argue that cloning should be banned because it might undermine genetic "diversity". But banning cloning for this reason is simply another form of eugenics! In light of the changes I foresee in the next 30 years, I think eugenics or cloning can't have more than a negligible effect upon the quality or quantity of world population.
Some people favor genetic manipulation only for the purpose of ensuring the birth of children free of genetic disease — not for eugenics. For example, a couple with an autosomal (non-sex chromosome) recessive genetic disease that has a 1-in-4 chance of producing a genetically defective child could be given the option of cloning an existing healthy child. Similarly, a nucleus could be transplanted from an oocyte containing mitochondrial DNA that would otherwise result in blindness. The fear of eugenics — even on a voluntary basis — has little basis in fact. The sperm bank of Nobel Prize-winning scientists (the Repository for Germinal Choice in Escondido, California) has resulted in less than 250 children in the 20 years since it was established.
Clones have been caracaturized as being human photocopies — zombies produced for use as slaves. But clones would really be more like time-delayed twins. Currently, one birth in 67 is twins, and the twins invariably have distinct personal identities. A "time-delayed" twin would be even more distinct. There would be no more grounds for treating a clone as a slave that for denying any other person the full charter of human rights. If those who oppose cloning on the grounds that "every human being has the right to be an individual" are to apply this principle consistently, then they would have to demand that one of every twin be forcefully aborted.
Some people fear that evil dictators might clone thousands of copies of themselves. Although this is possible, it seems unlikely to be in the interest of the dictator. A dictators clone would be more likely to overthrow him/her than anyone else. The dictator would have more incentive to clone thousands of his/her most docile subjects. But it would take a generation to do this and other technological change during that period would swamp any possible impact that this could have on global politics.
As a form of ego indulgence, cloning could be costly. If hundreds of clones were made of a beautiful film-star, her beauty would become more available to more men. But the laws of supply&demand dictate that the original would become less precious. So a prudent person concerned about undermining the value of her or his personal uniqueness might hesitate to produce too many clones. To protect against involuntary cloning of a person from a few cells left on a glass or handshake, the DNA Copyright Institute will store DNA information and register that information with the US Copyright Office for a fee of about $1,700. Of course a clone could not be killed, but the creator of the clone could be sued for damages — a deterrent.
Some people have protested that the possibility of cloning represents a threat to "genetic identity". But it might be possible to prevent people from being cloned involuntarily. People could be granted a permanent "copyright" on their DNA. Cloning could require written consent. Conversely, however, the right to ones own DNA implies that one should have the right to make a clone if one so chooses. A woman might be able to give birth to her own clone, but a man would require a surrogate mother (possibly his wife).
Why would anyone want to parent a clone of himself/herself? The intimacy that exists between twins is well-known. The role of genetics in personality is controversial, but persuasive evidence has been discovered that shyness, at least, is a genetically-determined personality attribute (fetuses with fast heartbeats tend to become shy babies). Persons who are genetically unique and experience alienation in the world may find the intimacy&closeness they crave by parenting a clone. The child would be a wanted child, and have a good chance of being raised with loving care. The option of cloning, rather than limiting diversity, will allow for the creation of new kinds of relationships. And it will give people the opportunity to personally explore (& learn-from) the meaning of their own genetic identity.
A childless woman could want to bear the clone of her infertile dying husband. Parents may want to clone a dying & beloved child. Those who condemn such passionate desires as "sick" or "perverted" are no different from other so-called moralists throughout the ages who have sanctified their own bigotry by the claim of divine inspiration. (Commandment Eleven: "Thou shalt not clone".) So-called moralists who accuse defenders of cloning of Nazi eugenics ignore the fact that it is the moralists themselves who are the fascists — invoking the power of the state to impose values on others and measuring human worth by the "naturalness" of conception.
Claims have been made that clones would be parented out of narcissism or for power. But why do people beget children now? Although love was a factor, Im certain that desire for power and enjoyment of power played an important role in my father wanting to have and rear children. And he regarded his children as his property. Similarly, I believe that my mothers desire to be loved and for social inclusion were important factors in her becoming a mother. I dont think that the motives to parent clones would be radically different than those that currently motivate people to have children. Based on the intense closeness that so often develops between twins, chances seem good that very loving parent-child relationships could be created in which there is high level of understanding&empathy of the parent for the child. I dont believe that love is evil — even self-love or love of a clone.
The objection that cloning would provide an option which favors the rich ignores the fact that wealth favors many options — better health-care, better education, vacations, fancy computer equipment and the possibility of larger families. In practice, the families of the wealthy do not seem particularly large now, and large families living on welfare are quite common in industrialized countries with generous "social programs".
A few lesbians have declared that men are now unnecessary. Single people of both sexes may feel that a new option for single-parenting is opening-up. Couples who would prefer to give birth to the clone of a lovable (but childless) aunt or uncle may now be able to do so. The unforeseen social consequences of cloning are not grounds for justifying a ban — and are more likely just another "trampling of rights" by creating a new "victimless crime". If fear of the unknown is allowed to dictate policy, the most predictable result is ignorance.
Arizona financer John Sperling, in an effort to have a clone of his beloved dog Missy, has contributed millions of dollars to the so-called Missyplicity Project at Texas A & M — through a new company called Genetic Savings and Clone. The group was successful in cloning a cat (dubbed "Copy Cat") in February 2002. Cats are evidently much easier to clone than dogs, and the project continues its efforts to clone Missy.
Since 1975 the San Diego Zoos Center for Reproduction of Endangered Species (CRES) has been banking fibroblast cells of endangered species in liquid nitrogen. The cells had been frozen simply to preserve genetic material for future scientific scrutiny. If clones could be produced from fibroblasts, the collection takes on new meaning. Unendangered species could be used as surrogate mothers for the endangered/extinct species cloned from the fibroblasts.
Taking this idea a step further, clones of transgenic animals might be bred which could act as surrogate mothers for human babies. If that were true, then human reproduction would essentially take-on the character of manufacture. It is this prospect which is the most horrifying to those who claim that cloning devalues human life. Clearly, however, a normal person should have no less rights by virtue of having had an animal rather than a human as a surrogate mother. But what if the cloned human was altered to have the brain of a dog? Or the brain of a lobster? Transgenic pigs would probably be a better source of human organs for transplant, but debrained human clones could be of great benefit for pharmaceutical companies wanting humanoid models for testing of experimental drugs.
Transgenic animal clones could be of service in more ways than
supplying human milk proteins. Wilmut has suggested that transgenic sheep
clones containing the human gene for cystic fibrosis could be used by
scientists to learn a great deal about that disease. Immunocompatible
neuronal or pancreatic tissue from transgenic animal clones could be
transplanted to humans to cure Parkinsons disease and diabetes.
Calves have now been cloned carrying human genes for immunoglobulin,
making them potential "drug factories" for producing antibodies.
Unlike vaccines, which can take weeks to stimulate immunity, the use of
such immunoglobulins could confer immediate immunity — of potential benefit
against bioweapons as well as in conventional medicine. Knowledge
gained by cloning research on the mechanisms of cell differentiation &
de-differentiation are very likely to yield insights into means to treat &
prevent cancer
— and into means to treat & prevent
.
Cloning could also have a big impact on animal food production.
Biotech start-up company
ProLinia Inc. has plans to make extensive genetic changes to farm
animals, adding genes to promote disease resistance and make meat less
fatty. The US Food and Drug Administration (FDA) has issued warnings to
biotech companies Infigen Inc. and
Advanced Cell Technology that
cloned animals are regarded as "experimental" — that meat &
milk of cloned animals are not FDA approved for use as foods.
Although some
stem cells are found in adults, the capacity of such cells is restricted,
e.g., hematopoietic stem cells only make blood cells. Stem cells from
early blastocyst embryos, however, can develop into any cell
type ("pluipotent"). When these pluripotent stem cells
were first isolated & cultured from human embryos in November 1998,
scientists predicted a new era of "regenerative medicine".
The current scientific challenge is to be able to (1) learn to
direct blastocyst
stem cells to differentiate into a specific desired cell type and
(2) learn to clone blastocyst embryonic stem cells from somatic cells.
"Right-to-life" advocates who believe that embryos have
"souls" and those opposed to human cloning oppose both kinds of
research.
Cloning is only one of a "family" of new reproductive
technologies. The first "test tube baby" (In-Vitro
Fertilization, IVF) was born in 1978 when eggs were
removed from the ovary of a British woman whose Fallopian tubes were
blocked. The egg was mixed with the fathers sperm and placed back
in the mothers uterus after the fertilized egg had divided into
64 cells. Babies born by the use of IVF increased in the United States
from about 6,000 to about 30,000 per annum in the decade of the 1990s.
Typically, IVF embryos are incubated 3 days before being placed
into the patients uterus, but 35% of births from this method are
twins (the norm is 3% twins), because more than one embryo is
placed in the uterus to ensure pregnancy. By incubating for
5 days rather than 3 some clinics are able to carefully
select the highest-quality embryo and increase the pregnacy rate
from one embyro from 61% to 76%.
Technologies now exist for "purifying" sperm so that the
sex of the child can be pre-selected. Haploidization would use
as skin cell from one parent to fertilize the egg or sperm of the
other parent — a technology similar to cloning insofar as it uses
nuclear transfer technology.
Most human stem cells used in research come from the inner cell mass
of blastocysts at about day 5 of gestation. Most of these blastocysts are
obtained from In-Vitro Fertilization clinics. Women who go to
IVF clinics are given hormone injections which cause their bodies to
generate 5-15 eggs during a monthly reproductive cycle instead of the
usual one egg. The eggs are surgically removed and mixed with the partners
sperm in lab dish — with the result that about 3/4 of the eggs result
in viable embryos. Several multi-celled embryos are implanted in the womans
uterus with the hope that one will survive — and the rest are often
cryopreserved in liquid nitrogen for possible future use.
US IVF clinics currently store 100,000-200,000 embryos. If the couple
divorces and cannot agree on the fate of the embryos, the embryos remain
in "limbo". As women age, it becomes increasingly unlikely they will become
pregnant again. Most of the excess embryos will never be used. Some are
donated to infertile couples. Most of the embryos donated for research
are used by the IVF clinics themselves to improve the in-vitro fertilization
process. Use for stem cell research involves costly shipment. It takes up to
10 embryos to make a stem-cell line (cell lines are tissue cultures of
cells that can reproduce themselves in a laboratory indefinitely). The
embryo cells usually do not survive the process of thawing, transfer to
culture and treatment with proteins that break-up the individual cells.
Therapeutic cloning is the process by which a human female
donates an egg, a skin cell from a prospective patient is injected
into the egg in such a way as to produce a clone and then the embryo
is allowed to grow until it contains about 100 cells. The stem cells
are then extracted from the embryo and used to differentiate into
heart cells, pancreatic cells, neurons, etc. — all of which could
be transplanted to the patient without fear of immunological rejection.
Stem cells are a potential cure for many degenerative diseases, including
diabetes, Parkinsons Disease, Multiple Sclerosis and Alzheimers Disease.
Cloning technology has already been used by
Advanced Cell Technology (ACT) to reverse cellular aging, to reproduce
an endangered species and to produce transplantable tissues. In the
latter process, somatic cells are dedifferentiated to germ cells, and
then redifferentiated to stem cells and then to target tissues. This
use of cloning technology could produce tissues and even organs for
transplant into a donor who provided somatic starting cells (with
little chance of immunological incompatibility). ACT was thrust into
media limelight by its 25-Nov-2001 announcement of having replaced
transplanted a nucleus into a human egg and having coaxed the egg
into dividing into six cells — which died before becoming a viable
source of stem cells. Significantly, ACT failed
in all attempts to transfer the nucleus from adult skin cells — only
succeeding in transferring a nucleus from ovary support cells. Opponents
of therapeutic cloning are concerned that improvements in these technologies
will eventually make human reproductive cloning technology more feasible.
Researchers at the Xiangya Medical College in China claim to
have cloned human embryos two years earlier than ACT, but this claim was
not verified by publication in a peer-reviewed journal recognized by
Western scientists. Biotechnology has strong government backing in China,
and few in that nation equate embryo cells with a human being. When a
United States delegation to the United Nations argued for bans on all
laboratory cloning, they met with firm opposition from China. Singapore
has been attempting to establish itself as the stem-cell-research capital
of the world through massive funding for biotechnology education &
research and a law that permits cloned embryos to be kept for up to 14 days.
Alan Colman, head of the team that cloned Dolly in Scotland was lured to
move to Singapore.
In February 2004 South Korean researchers succeeded in creating
human embryos by placing adult cell nuclei into human eggs to create embryonic
stem cells. A 2004 attempt to ban cloning globally was strongly supported
at the United Nations by the United States, but failed because of opposition
from South Korea, Japan, Australia, India, Belgium and the United Kingdom.
Proponents are drafting new proposals.
Regulations concerning embryo research in Israel are also very liberal
— and Israel has a large number of IVF clinics. Of the first 12 publications
on human embryonic stem cells, 10 included Israeli authors. Researchers at
the Israel Institute of Technology (Technion) have created heart cells and
insulin-producing cells from human embryonic stem cells, a process
that could be lifesaving for
heart attack
patients and diabetic patients.
But the Israelis had no control over differentiation, they simply let the
cells grow and picked-out the ones they wanted. Work at Hebrew University
in Jerusalem led to the discovery of the role played by growth factors
in prompting human embryonic stem cells to differentiate into different
cell types.
The US House of Representatives passed a bill which would criminalize
therapeutic cloning, but still allow stem cells to be obtained from
IVF clinics. US President Bush supported use of federal funds only for
research on human embryonic stem cell (hESC) lines existing before the
beginning of his speech on the subject on 9-Aug-2001. He estimated the
number of such cell lines to be "more than 60", but 20 months
later only 11 hESC lines were available for distribution — which does
not provide enough genetic diversity to discover novel pathways of
differentiation. Moreover, all the pre-Aug-2001
hESC had been created using mouse embryonic fibroblast feeder cells to
support them. Human feeder cells have since been developed, which
would not have the possibility of contamination with mouse viruses and
proteins or the severe restrictions imposed on xenotransplantaion products
imposed by the FDA. The moral superiority of using embryos destroyed
prior to Aug-2001 is questionable, and the technical inferiority of
the resulting hESC lines is unquestionable.
British law forbids cryopreserved embryos
from IVF clinics to be stored for more than 5 years, even though the
Catholic Church strongly condemns destruction of cryopreserved embryos.
British Parliament has allowed therapeutic cloning and creation of human
embryos from sperm & egg for research purposes — though the embryos
are not permitted to last more than 14 days. But the Parliament later
enacted legislation that mandates a prison sentence of up to ten years
for anyone cloning a human — the same sentence the American legislation
would apply to any scientist attempting therapeutic cloning.
Prior to 1869 the Catholic Church followed Aristotle in the belief
that an embryo does not become sufficiently human to acquire a soul
until day 40 for males, and day 90 for females.
Only in the 17th century were egg & sperm (and
the role they play in conception) identified by science (see
An Amazing 10 Years: The Discovery of Egg and
Sperm in the 17th Century). In 1869 Pope Pius IX excommunicated all who
procured abortions after the moment of conception — implying that
a fertilized egg has a soul. In
1974 (Declarato de Abortu Procurato) the Catholic Church
identified a person with a genome — a remarkable bit of materialism
considering that individuality is not even established until two or three weeks
after conception,
beyond which the formation of twins can no longer occur. A fertilized egg
does not invariably become one or more persons — sometimes it becomes
a clump of undifferentiated tissue in the uterus
(molar pregnancy). For those who believe that a zygote does not
become a human being until some time after conception,a variety of biological
milestones have been proposed, including the time when the embryo implants in
the uterus (about a week after conception), after twinning is no longer possible,
when fetal movement ("quickening") first occurs, when heartbeat begins,
when electrical activity is first detected in the central nervous system, or
when the cerebral cortex develops.
If respect for life is the decisive criterion, then the lives of
all the sperm that perished without fertilizing the egg must be
respected. The Catholic Church should specify at what point of the
fertilization process a zygote acquires a soul (When the sperm
penetrates the egg? When the male pronucleus is formed? When the
DNA of each pronucleus aligns?) and the means by which they make
a certain determination. Respect for life should not overlook all
of the human patients whose lives could be saved and suffering
alleviated by therapeutic cloning.
If a zygote is regarded to have a soul because it is a "potential human being",
so should a sperm or egg because they are potentially human. On the other hand, if the sperm or
egg cannot be regarded as potentially human until united, how can a zygote be regarded as having
an individual soul when twins can occur between two and three weeks after the zygote is formed? If science can
make a zygote from a skin cell, then the skin cell is potentially human also, and must be regarded
as having a soul.
Those who advocate developing potentially life-saving technologies associated with
cloned embryonic stem cells are accused of "playing God", but those who would prevent
these technologies are "playing God". There is no scriptural authority for forbidding stem
cell research and there is no evidence that God means to prevent the use of life-saving technologies.
Those who claim to speak for God should take care that they are not arrogantly asserting their own
prejudices — for which they may later learn humility.
Religious opponents of cloning often regard the fertilization
of a human egg by a sperm and the resulting developing embryo as a
holy process not to be tampered with by Humankind through
artificial means. Creating a human by In-Vitro Fertilization (IVF)
may be only slightly more artificial than creating a human by cloning.
Although many religious people oppose IVF & cloning, few have
declared that a human created by IVF or cloning would have no soul,
be evil or be unloved by God. The Catholic Church morally condemns
In-Vitro Fertilization, cryopreservation of embryos and the destruction
of embryos — but does not oppose the medical use of embryo tissue which
has been obtained from spontaneous abortion (see SCIENCE 293:211,
13-July-2001).
Many Catholics favor stem-cell research — as do a significant number of
abortion opponents (many of whom believe that obtaining stem cells from
IVF clinic embryos would reduce the temptation to obtain stem cells from
aborted fetuses). But pressure from Catholic constituents was enough
to cause the American Heart Association to rescind a decision to
provide funding for embryonic stem cell research. Many scientists regard
the use of stem cells from abortions as no different from the use of
cadavers by medical schools.
The controversy over stem cells has prevented much federally-funded
research into potential applications. Most of the US patents for embryonic
stem cell technologies are held by one company: Geron Corporation. Geron
cultivates stem cell lines, but cannot distribute them to many institutions
which fear their federal grants could be jeopardized. Limiting federal
researchers to the use of existing cell lines could prevent the development
of many new cell lines which could potentially be of use — and would
enhance the commercial interests of companies which have developed existing
cell lines. And it is likely that harmful genetic mutations will
accumulate in existing cell lines rendering them useless. Newer and better
cell lines would be desirable because most of the existing cell lines have
been cultured with animal cells or serum that could be a risk to human health.
(Cross-species cloning is also problematic because mitochondria in the egg
receiving the cell to be cloned are not sustained by the nucleus.)
Some people who would
not otherwise oppose therapeutic cloning fear that such technology could too
easily be diverted into cloning humans. Others who favor therapeutic cloning
believe that it should only be permitted with fearsome legal consequences
for any who attempt human cloning. And others believe that therapeutic
cloning is such a "slippery slope" leading inevitably to a
pandora's box of biotechnology "nightmares" — such as human
cloning, children engineered to custom specifications and brainless
humans being grown for spare body parts — that it is better to ban all
forms of cloning and to live with the missed opportunity of curing a
myriad of diseases than to risk the "nightmares"
The strongest argument against immediate attempts to perfect human
cloning is the fact that the process is far from perfected. After all, the
277 adult cells used to create Dolly resulted in one live birth and 12
stillbirths. The production of so many deformed human fetuses and babies
would not be tolerated. Adult cells of one phenotype could easily harbour
mutations of unexpressed genes, which would become expressed upon the
de-differentiation and re-differentiation of cloning. Moreover, the cells
in Dolly are 6 years older than they would be.
Even if it were possible to detect defects very early, a firestorm of
protest would ensue from anti-abortionists who believe that humanity begins at
the moment of conception. Possibly for this reason, and probably also for
weaker reasons, the member governments of the World Health Organization have
unanimously passed a resolution declaring human cloning to be "ethically
unacceptable and contrary to human integrity and morality". US President
Bush's bioethics advisor, Dr. Leon Kass, asserted that cloning "robs
us of our humanity" and "risks coarsening our moral
sensibilities". In addition to his opposition to cloning, Kass is
an anti-life-extensionist
who has written, "I think we make a huge
mistake if we try to push the life expectancy out to 150 years or longer".
(It cannot be an accident that most professional ethicists have obnoxious
moral standards — what drives a person to professionally meddle in other
peoples lives?).
Even if major countries do outlaw human cloning, there was never much
doubt that offshore/underground human cloning research would continue. A
UFO cult known as the
Realian Movement organized a company in 1997 to clone humans for those
who are willing to pay, a service called
CLONAID®.
Raelians believe that aliens from a UFO contracted the French journalist
Rael informing him that they had created humans from DNA 25,000 years ago.
The sect has a UFO theme park near Montreal, Canada and is known for
uninhibited sexual practices. Numerous members are willing to allow
their bodies to be used for surrogate motherhood & cloning — which
they believe is the key to immortality.
In March 2001 the Italian Dr. Severino Antinori and the American
Professor Panayiotis Zavos announced that they would begin work on
creation of a human clone in a secret laboratory at an undisclosed
Mediterranean country. Implantation was scheduled to begin in October
of the same year. Dr. Antinori has already achieved fame in helping a
62-year-old woman to give birth. Dr. Zavos said that unlimited funds
were available for the project from private donors.
.
Aside from those who oppose cloning in principal, there are many
scientists who believe that much more work should be done with animals
before experimenting with humans because of the risk of stillbirths,
miscarriages and deformed/abnormal children. Only 10% of cells
created by nuclear transfer develop into balls of cells called
blastocysts. Of blastocysts implanted in the womb, only one-fifth of
the pregnancies are carried to term. And, once born, half the seemingly
normal cloned cows & sheep drop dead within three weeks due to
fatal flaws in heart muscle or kidney. The surrogate mothers of these
clones might also be at risk, because the clones are often abnormally
large — with increased frequency of miscarriage [SCIENCE 291:2061-2062
& 2552 (2001)]. Somatic cells do not have the DNA repair capabilities
of meiosis, which can make them less reliable as progenitors. In normal
development early genes (genes that control the early stages of cell
differentiation) are inactivated by cytosine methylation — resulting in
high methylation of the adult genome. Cloning should fully demethylate
the adult cell, but this process is often faulty. There is currently no
test for methylation abnormalities
[SCIENCE 292:31 (2001)]. Even when cloning is done using nuclear
transfer from embryonic stem cells, the animals that survive
have subtle abnormalities in gene expression and, hence, subtle
physiological abnormalities [SCIENCE 293:95-97 (2001)].
If cloning technology is not perfected on animals before it is
attempted on humans, the prospect of many stillbirths, abortions and
genetically diseased human babies raises serious humanitarian concerns.
And these humanitarian concerns will provide fuel for the technophobic
anti-cloning activists who may be in a position to block the many avenues
of research associated with cloning that have such great potential
to combat disease & aging.
Although human cloning would
be valuable in the long run as a source of new information, in the
immediate future it is more of a danger to scientific advancement than
a benefit. This does not justify authoritarian efforts to
prohibit researchers from cloning human cells — out of fear of
increasing the potential for cloning humans. All biomedical
research increases the potential for cloning humans — but more
important is the potential for saving &
extending human lives.
For summaries of legislation in different countries concerning
cloning and other controversial biotechnologies see
http://strategis.ic.gc.ca/SSG/bb00003e.html .
For a peer-reviewed journal, see
Cloning and Stem Cells.
For the latest news about cloning, go to the
Yahoo Science Full Coverage Cloning website.
For my views on genetically modified organizms (GMOs), see my webpage:
Genetically Modified Foods .