CLONING
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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 obsta-
cles are, however, greater than most people recog-
nize. Experts in the field doubt that human repro-
ductive cloning can be safely pursued, at least for
several decades. In Dolly’s case, it took 277 at-
tempts 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 associ-
ated with cloning is that the clone, having nuclear
DNA that may be many years old, will age prema-
turely, at least in some respects. Mammalian pro-
creation is a profoundly complicated process, as
yet little understood, with subtlety of communica-
tion 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 be-
yond the ability of science as of 2002. Expert pan-
els of scientists all strongly condemn the use of
SCNT to produce a human baby.
Therapeutic cloning
Cloning, however, may have other human applica-
tions beside reproduction, and many scientists en-
dorse 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 pos-
sibility of combining nonreproductive cloning with
embryonic stem cell technologies. Human embry-
onic stem cells, first isolated in 1998, appear prom-
ising as a source of cells that can be used to help
the human body regenerate itself. Based on re-
search performed in mice and rats, scientists are
optimistic that stem cells may someday be im-
planted in human beings to regenerate cells or tis-
sues, 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 em-
bryos, 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 re-
generative 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 im-
mune 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 de-
stroyed. 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 im-
mune response.
Religious concerns about cloning
While many believe the potential benefits justify
research in therapeutic cloning, some object on re-
ligious grounds. Many Roman Catholic and Ortho-
dox 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 nonrepro-
ductive 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