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What are the issues related to cloning?
Questions
What is cloning?
Sources
Drell, Daniel, and Marissa Mills.
"Cloning Fact Sheet." Oak Ridge
National Laboratory. 30 July 2008.
25 Sep. 2009
<http://www.ornl.gov/sci/techresou
rces/Human_Genome/elsi/cloning.s
html>.
How/Why is cloning
performed?
One of the biggest disadvantages of cloning is that
the technology is still so uncertain. Dolly the sheep,
the first mammalian clone, was born in 1996. While
she was initially successful, she died young of a
disease not normally seen in sheep of her age.
Scientists are still unsure of any genetic mutations
that might occur when an animal is cloned. Also,
while Dolly was a successful clone, there were
hundreds of failed clones before she was made,
including several dead fetuses. Other cloned
animals have turned out horribly deformed.
Losing gene diversity is another of
the disadvantages of cloning.
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.
To "clone a gene," a DNA fragment containing
the gene of interest is isolated from
chromosomal DNA using restriction enzymes
and then united with a plasmid that has been cut
with the same restriction enzymes. When the
fragment of chromosomal DNA is joined with its
cloning vector in the lab, it is called a
"recombinant DNA molecule." Following
introduction into suitable host cells, the
recombinant DNA can then be reproduced along
with the host cell DNA.
"What is Cloning?." Learn Genetics.
15 Sep. 2009
<learn.genetics.utah.edu/content/te
ch/cloning/whatiscloning/>
What exactly is cloning?
Cloning is the creation of an organism that is an
exact genetic copy of another. This means that
every single bit of DNA is the same between the
two!
You might not believe it, but there are human
clones among us right now. They weren't made
in a lab, though: they're identical twins, created
naturally. Below, we'll see how natural identical
twins relate to modern cloning technologies.
What are the side effects?
What animals have been
cloned?
Scientists have been cloning animals for many
years. In 1952, the first animal, a tadpole, was
cloned. Before the creation of Dolly, the first
mammal cloned from the cell of an adult animal,
clones were created from embryonic cells. Since
Dolly, researchers have cloned a number of large
and small animals including sheep, goats, cows,
mice, pigs, cats, rabbits, and a gaur. All these
clones were created using nuclear transfer
technology. Hundreds of cloned animals exist
today, but the number of different species is limited.
Attempts at cloning certain species have been
unsuccessful. Some species may be more resistant
to somatic cell nuclear transfer than others. The
process of stripping the nucleus from an egg cell
and replacing it with the nucleus of a donor cell is a
traumatic one, and improvements in cloning
technologies may be needed before many species
can be cloned successfully.
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. The U.S. Congress has considered 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.
1. High failure rate
Research advances over the past decade have told
us that, with a little work, we humans can clone just
about anything we want, from frogs to monkeys and
probably even ourselves!
So, we can clone things, but why would we want
to? Let's look at some of the reasons people give to
justify cloning.
1. Cloning for medical purposes
Of all the reasons, cloning for medical purposes
has the most potential to benefit large numbers of
people. How might cloning be used in medicine?
Cloning animal models of disease
Much of what researchers learn about human
disease comes from studying animal models such
as mice. Often, animal models are genetically
engineered to carry disease-causing mutations in
their genes. Creating these transgenic animals is a
time-intensive process that requires trial-and-error
and several generations of breeding. Cloning
technologies might reduce the time needed to make
a transgenic animal model, and the result would be
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. Or you can look at it as 970 to 999 failures in
1000 tries. That's a lot of effort with only a speck of
a return!
2. 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.
The prospect of cloning humans is highly
controversial and raises a number of ethical, legal
and social challenges that need to be considered.
To explore some of these, see What are Some
Issues in Cloning?
Why would anyone want to clone humans? Some
reasons include:
♥
To help infertile couples have children
♥
To replace a deceased child
From a technical standpoint, before humans are
cloned, we need to have a good idea of the risks
involved. How sure can we be that a cloned baby
will be healthy? What might go wrong?
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a population of genetically identical animals for
study.
3. Abnormal gene expression patterns
Cloning stem cells for research
Stem cells are the body's building blocks,
responsible for developing, maintaining and
repairing the body throughout life. As a result,
they might be used to repair damaged or
diseased organs and tissues. Researchers are
currently looking toward cloning as a way to
create genetically defined human stem cells for
research and medical purposes. To see how this
is done, see Creating Stem Cells for
Research, a component of the Stem Cells in
the Spotlight module.
"Pharming" for drug production
Farm animals such as cows, sheep and goats
are currently being genetically engineered to
produce drugs or proteins that are useful in
medicine. Just like creating animal models of
disease, cloning might be a faster way to produce
large herds of genetically engineered animals.
Find out more about this research in the feature
articlePharming for Farmaceuticals .
2. Reviving Endangered or Extinct Species
Have you seen Jurassic Park? In this feature film,
scientists use DNA preserved for tens of millions of
years to clone dinosaurs. They find trouble,
however, when they realize that the cloned
creatures are smarter and fiercer than expected.
Could we really clone dinosaurs?
In theory? Yes. What would you need to do this?
♥
A well-preserved source of DNA from
the extinct dinosaur, and
♥
A closely related species, currently
living, that could serve as a surrogate
mother
In reality? Probably not. It's not likely that dinosaur
DNA could survive undamaged for such a long
time. However, scientists have tried to clone
species that became extinct more recently, using
DNA from well-preserved tissue samples.
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.
4. Telomeric differences
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.
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"Cloning-Article."GoldBamboo.com Your Integrative Health and
Wellness Resource. 22 July 2006.
16 Sep. 2009
<http://www.goldbamboo.com/topi
c-t2730-a1-6Cloning.html>.
"Cloning." Free Website Hosting –
Angelfire free website templates to
make your own free website. 14
Sep. 2009
<http://www.angelfire.com/la/Isla
micView/Cloning.html>.
Cloning is the process of creating an identical
copy of an original. A clone in
the biological sense, therefore, is a
single cell (like bacteria, lymphocytes etc.) or
multi-cellular organism that has been directly
copied from and is therefore genetically identical
to another living organism. Sometimes this term
can refer to "natural" clones made either when
an organism reproduces asexually or when two
genetically identical individuals are produced by
chance (as with identical twins), but in common
parlance, a clone is an identical copy created
intentionally. (See also: clone (genetics).
The success rate of cloning has been low: Dolly the
sheep was born after 277 eggs were to create 29
embryos, which only produced three lambs at birth,
only one of which lived, Dolly. 70 calves have been
created from 9,000 attempts and one third of them
died young; Prometea took 328 attempts, and,
more recently, Paris Texas was created after 400
attempts. Notably, although the first clones were
frogs, no adult cloned frog has yet been produced
from a somatic adult nucleus donor cell.
Cloning is quite inefficient and usually there are
over 600 to 1000 nuclear transfers before one is
able to grow into a stem cell. This inefficiency is
thought to be due to geneticimprinting in the cloned
adult cell that interferes with the
correct gene expression in the embryo. Even those
animals that are successfully cloned are not as
healthy as the original animal. For example, Dolly
had arthritis and sign of premature
aging. See methylation and epigenetic.
Cloning is done by the use of the nucleus of an egg
and selected DNA from the one being cloned.
These two are than fused together with the use of
an electrical current. This cell than grows into a
genetic duplicate and placed into the womb until full
term into a normal human being. At least this is the
theory.
So a clone is not an identical person to the one
being cloned in all respects. Just as an identical
twin is not the twin in all respects. They are two
distinct human beings, if one dies the other lives on.
Cloning should not be mistaken with the ability to
live forever. It is just a genetic duplicate, the two
would look the same, have some of the same likes
and dislikes but would be two separate distinct
human beings.
SUMMARY
Human cloning
Main article: Human cloning
Human cloning is the creation of a genetically
identical copy of an existing, or previously existing
human or growing cloned tissue from that
individual. The term is generally used to refer to
artificial human cloning; human clones in the form
of identical twins are commonplace, with their
cloning occurring during the natural process of
reproduction.
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