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Cloning
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A
Clone Again, Unnaturally
Cloning scares me. Then again,
so do spiders.
What I found after
my brief research for this article, is that there are
different types of cloning. And just like spiders,
some types of cloning I should be wary of, but many may be considered beneficial.
There are plenty of moral and
ethical concerns associated with cloning. A good
understanding of the basic science and processes that
lay behind cloning and what they can do, will help us
as a society to make better decisions regarding its
use.
What is
Cloning?
Cloning - an
umbrella term to describe different processes for
duplicating biological material.
When the media report on cloning in the
news, they are usually talking about only one type called
"reproductive cloning". There are different types of cloning
however, and cloning technologies can be used for other
purposes besides producing the genetic twin of another
organism.
A basic understanding of the different
types of cloning is key to taking an informed stance on
current public policy issues and making the best possible
personal decisions.
Reproductive Cloning
Reproductive cloning is a technology
used to generate an animal that has the same nuclear
DNA as another currently or previously existing
animal. Dolly was created by reproductive cloning
technology.
Therapeutic Cloning
Therapeutic cloning, also called
"embryo cloning," is the production of human embryos
for use in research. The goal of this process is not
to create cloned human beings, but rather to harvest
stem cells that can be used to study human development
and to treat disease.
DNA Cloning
The terms "recombinant DNA
technology," "DNA cloning," "molecular cloning" or
"gene cloning" all refer to the same process: the
transfer of a DNA fragment from one organism to a
self-replicating genetic element such as a bacterial
plasmid. The DNA can then be propagated in a foreign
host cell. This technology has been around since the
1970s, and it has become a common practice in
molecular biology labs today.
Cloning Animals
Farmers and ranchers are cloning
animals for the same reason they selectively breed
them, to reproduce better livestock.
This type of cloning is an assisted
reproductive technology that allows livestock breeders
and others to create identical twins of their best
animals. This breeding technique does not change the
genetic make-up of the animal.
CloneSafety.org
Cloning
Humans
Should humans be cloned? Physicians from
the American Medical Association and scientists with the
American Association for the Advancement of Science have
issued formal public statements advising against human
reproductive cloning. Currently, the U.S. Congress is
considering the passage of legislation that could ban
human cloning.
Due to the inefficiency of animal cloning (only about 1 or
2 viable offspring for every 100 experiments) and the lack
of understanding about reproductive cloning, many
scientists and physicians strongly believe that it would
be unethical to attempt to clone humans. Not only do most
attempts to clone mammals fail, about 30% of clones born
alive are affected with "large offspring syndrome" and
other debilitating conditions. Several cloned animals have
died prematurely from infections and other complications.
The same problems would be expected in human cloning. In
addition, scientists do not know how cloning could impact
mental development. While factors such as intellect and
mood may not be as important for a cow or a mouse, they
are crucial for the development of healthy humans. With so
many unknowns concerning reproductive cloning, the attempt
to clone humans at this time is considered potentially
dangerous and ethically irresponsible. 
Is
Cloning an Organism The Same as Cloning a Gene?
You've heard about cloning animals -
sheep, mice, even house pets - in the news. From time to
time, you may have also heard about researchers cloning,
or identifying, genes that are responsible for various
medical conditions or traits.
What is the difference?
Ethical Concerns
The announcement of Dolly sparked
widespread speculation about a human child being
created using somatic cell nuclear transfer. Much of
the perceived fear that greeted this announcement,
centered on the misperception that a child or many
children could be produced who would be identical to
an already existing person. This fear is based on the
idea of "genetic determinism" -- that genes alone
determine all aspects of an individual -- and reflects
the belief that a person's genes bear a simple
relationship to the physical and psychological traits
that compose that individual. Although genes play an
essential role in the formation of physical and
behavioral characteristics, each individual is, in
fact, the result of a complex interaction between his
or her genes and the environment within which he or
she develops.
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Dolly - First Mammal To Be Cloned
Dolly's success is truly remarkable because it proved
that the genetic material from a specialized adult cell,
such as an udder cell programmed to express only those
genes needed by udder cells, could be reprogrammed to
generate an entire new organism.
Before this demonstration, scientists believed that
once a cell became specialized as a liver, heart, udder,
bone, or any other type of cell, the change was permanent
and other unneeded genes in the cell would become
inactive. Some scientists believe that errors or
incompleteness in the reprogramming process cause the high
rates of death, deformity, and disability observed among
animal clones.
The
Ethics of Cloning
Morally serious people may differ in
their final judgment of the ethics of cloning for
biomedical research. But they do – or should – agree on
this: that fidelity both to the highest moral and human
aspirations of science and medicine and to the moral
standards of the wider community requires that we consider
not only why and how to proceed with new lines of
research, but also whether there might be compelling
reasons not to do so or certain limits that should be
observed. Both the facts (scientific and moral) and our
ethical principles must be consulted in trying to judge
what is best.
The President's Council on Bioethics
New international guidelines for stem cell science
The first international guidelines on human
embryonic stem cell research, echo public opinion in calling for a ban on human
reproductive cloning.
Cloning to Save
Endangered Species Some people see cloning as
a way to remedy the problem of endangered species, and to
reproduce those that have already disappeared.
Online Articles
First wolves are cloned in South Korea
What are some of the upsides and downsides of cloning,
especially the cloning of endangered or extinct species?
Cloning endangered species
What role for conservation cloning?
Raising the dead
How
Successful
is Cloning?
When we hear of cloning successes, we learn about only the
few attempts that worked. What we don't see are the many,
many cloning experiments that failed.
Cloning animals shows us what might happen if we try to
clone humans.
High failure rate -
Cloning animals through somatic cell nuclear transfer is
simply inefficient. The success rate ranges from 0.1
percent to 3 percent, which means that for every 1000
tries, only one to 30 clones are made.
Problems during later development
- Cloned animals that do survive tend to be much bigger at
birth than their natural counterparts. Scientists call
this "Large Offspring Syndrome" (LOS). Clones with LOS
have abnormally large organs. This can lead to breathing,
blood flow and other problems.
Because LOS doesn't always occur, scientists cannot
reliably predict whether it will happen in any given
clone. Also, some clones without LOS have developed kidney
or brain malformations and impaired immune systems, which
can cause problems later in life.
Abnormal gene expression patterns - Are the
surviving clones really clones? The clones look like the
originals, and their DNA sequences are identical. But will
the clone express the right genes at the right time?
In Click and Clone, we saw that one challenge is to
re-program the transferred nucleus to behave as though it
belongs in a very early embryonic cell. This mimics
natural development, which starts when a sperm fertilizes
an egg.
In a naturally-created embryo, the DNA is programmed to
express a certain set of genes. Later on, as the embryonic
cells begin to differentiate, the program changes. For
every type of differentiated cell - skin, blood, bone or
nerve, for example - this program is different.
In cloning, the transferred nucleus doesn't have the same
program as a natural embryo. It is up to the scientist to
reprogram the nucleus, like teaching an old dog new
tricks. Complete reprogramming is needed for normal or
near-normal development. Incomplete programming will cause
the embryo to develop abnormally or fail.
Telomeric differences
- As cells divide, their chromosomes get shorter. This is
because the DNA sequences at both ends of a chromosome,
called telomeres, shrink in length every time the DNA is
copied. The older the animal is, the shorter its telomeres
will be, because the cells have divided many, many times.
This is a natural part of aging.
So, what happens to the clone if its transferred nucleus
is already pretty old? Will the shortened telomeres affect
its development or lifespan?
When scientists looked at the telomere lengths of cloned
animals, they found no clear answers. Chromosomes from
cloned cattle or mice had longer telomeres than normal.
These cells showed other signs of youth and seemed to have
an extended lifespan compared with cells from a naturally
conceived cow. On the other hand, Dolly the sheep's
chromosomes had shorter telomere lengths than normal. This
means that Dolly's cells were aging faster than the cells
from a normal sheep.
To date, scientists aren't sure why cloned animals show
differences in telomere length.
Read more of this article at
The
University of Utah, Genetic Science Learning Center
Cloning Articles
Cloning 101
Human cloning is perhaps the most
controversial reproductive technology
Scientists create a sheep that's 15%
human
Human Cloning - the Risks
Risks of Cloning
Animal cloning and the FDA
Cloning: Right or Wrong
Human Cloning -the Risks
Upsides and downsides of cloning
Cloning Also Raises Health Concerns
Cloning Embryonic Stem Cells
The Perils of Cloning
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