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cloning للصف الثالث ثنوي علمي تقرير

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cloning للصف الثالث ثنوي علمي تقرير

مُساهمة من طرف HeMa PoP في الجمعة مارس 21, 2008 6:11 pm

Introduction

There
is a lot of power to cloning. But, should we make use of cloning with
no restrictions? Should cloning be used on humans? How and when should
cloning be used? Before we start to answer these questions, we should
learn more about cloning..

What is Cloning?
1- The
dictionary says cloning is the technique of producing a genetically
identical duplicate of an organism. A clone is said to be all
descendants derived asexually from a single individual, as by
cuttings(like in plants), bulb divisions (like in tulips or daffodils)
, by fission, by mitosis, or by parthenogenesis reproduction. Here are
some examples

2-Cloning is the process of making a genetically
identical organism through nonsexual means. It has been used for many
years to produce plants (even growing a plant from a cutting is a type
of cloning). Animal cloning has been the subject of scientific
experiments for years, but garnered little attention until the birth of
the first cloned mammal in 1997, a sheep named Dolly. Since Dolly,
several scientists have cloned other animals, including cows and mice.
The recent success in cloning animals has sparked fierce debates among
scientists, politicians and the general public
History and Science
Cloning
(from the Greek word klon, a twig or slip) is a natural process of
asexual reproduction found in many plants and some animals. When
strawberry plants send out runners that set roots and turn into new
plants, this is an example of a plant naturally cloning itself. Even
artificial cloning is not entirely new. For hundreds of years gardeners
have taken slips (small shoots or twigs cut from plants) and rooted
them to produce new plants in a process that could also be described as
cloning. Then in the 1970s scientists began experiments in artificial
cloning with frogs and toads, and subsequently with other animal
embryos. But it was not until the successful SCNT cloning of the sheep
"Dolly," performed in 1996 and formally announced in February 1997 by
the Roslin Institute in Scotland, that it became clear something
similar might be possible with mammals.
Mammals have two kinds of
cells: somatic cells (many of which can reproduce themselves by clone
like division, but only themselves and not a whole organism) and sex
cells (which come in two forms, ovum in females and sperm in males).
The SCNT process works as follows: The nucleus is removed from a
somatic cell of either a female or a male. An unfertilized ovum is
taken from a female and has its nucleus removed and then replaced with
the somatic cell nucleus. The resulting ovum with a somatic cell
nucleus is then stimulated and implanted in a female womb to grow to
term. The resulting offspring is genetically identical to the
individual that was the source of the original somatic nucleus.
The
technology of cloning is thought to be feasible in many mammalian
species, including humans. As of 2005, successes in cloning of many
species have been achieved. But neither the cloning of primates nor of
humans has been successful as yet. Human somatic cell nuclear transfer,
if successful in producing offspring, would not be "duplication"
because identical genomes do not produce identical phenotypes.
Nevertheless, Korean scientists have used cloning technology to produce
cloned embryos, and subsequent experiments have furthered such
technologies, which are aimed at producing embryonic stem cells On
January 8, 2001, scientists at Advanced Cell Technology, Inc.,
announced the birth of the first clone of an endangered animal, a baby
bull gaur (a large wild ox from India and southeast Asia) named Noah.
Although Noah died of an infection unrelated to the procedure, the
experiment demonstrated that it is possible to save endangered species
through cloning.

Human Cloning
Human cloning is the process
of transplanting nuclear DNA from an adult individual into an egg where
the nucleus has been removed. The egg grows into an embryo to produce
an exact copy of the nuclear genome from the donor DNA without ever
needing sperm to fertilize the egg. Dr. Ian Wilmut coined this
technique somatic cell nuclear transfer after the first successful
attempt at cloning a mammal, a sheep named Dolly, using adult somatic
cells.
Advocates of human cloning suggest that somatic cell nuclear
transfer may be a useful method for solving infertility problems or
preventing inherited mitochondrial disease in offspring. For example,
if a husband is infertile or a wife has a mitochondrial disease, the
wife's somatic nuclei could be transferred into the cytoplasm of a
donor egg and implanted into the wife's womb without ever needing
sperm. This is the same procedure that was used to clone the sheep,
Dolly, in Scotland at the Roslin Institute in 1997; however, Dolly
developed in the womb of her foster mother who donated the cytoplasm
rather than her genetically identical mother. In both situations, the
cloned offspring is not an exact copy of the mother's somatic nuclei
because of the mitochondrial DNA located in the cytoplasm of the donor
eggs. Some researchers argue that somatic cell nuclear transfer is not
a cloning technique, but rather a method for treating infertility.
Other
scientists claim that attempting to clone humans would result in
miscarriages, stillbirths, and major organ defects that would
eventually lead to death. Currently, 98% of animals that are cloned die
during the gestational period and many of the animals that are born
suffer from birth defects. Researchers at the Roslin Institute made 277
attempts before they were able to successfully create Dolly. Although
Dolly has proven to be a normal sheep, researchers have discovered that
Dolly has shorter than normal tips on the ends of her chromosomes
called telomeres. Telomeres shorten with age suggesting that Dolly may
have a shorter life span than the average sheep. Cloning does not
result in genetic defect, but rather something goes array during the
reprogramming process that stimulates life. Usually reprogramming is
stimulated during fertilization when the sperm unites with the egg;
however, fertilization does not occur during cloning and electrical
stimulation is necessary to generate the reprogramming process.
According
to Advanced Cell Technology (ACT), the first human cloned embryo was
pioneered in November 1998. DNA was taken from the skin on a man's leg
and transplanted into the egg of a cow that grew for twelve days before
scientists aborted the experiment. Some scientists claim that human
cloning has begun at the Institute for Reproductive Medicine and
Science of St. Barnabas Medical Center in New Jersey. Others argue that
genetically modifying babies does not amount to human cloning. Fifteen
babies were born as a result of cytoplasm from the eggs of donor
mothers being transplanted into the eggs of infertile women.
Mitochondria in the cytoplasm contain their own genetic sequence that
was thought to be the cause of infertility. Sperm from the father was
then injected to fertilize the egg. This technique called the ooplasmic
transfer was further used at other facilities to produce fifteen more
babies.
Supporters of human cloning contend that cloning would be
beneficial as a therapeutic treatment for people with diseases and
other medically related problems. Stem cell technology is a cloning
based method used to grow stem cells in order to develop specialized
tissues that may help repair dead or damaged tissues and organs. For
example, healthy heart cells could be cloned and injected into damaged
areas of the heart in a heart attack victim. Some researchers propose
that cloning could be used to treat such problems as nerve damage,
diabetes, Parkinson's disease, Alzheimer's disease, heart failure,
severe burns, lung damage, liver failure, kidney failure, and cancer.
Advocates of human cloning reason that cloning one's own cells rather
than transplant organs or engineering tissues to replace dead or
damaged ones, will prevent rejection from their immune system. Other
supporters feel that producing cloned offspring will allow couples to
have biological children that they would have otherwise been unable to
conceive because of either infertility problems or genetic defects.
Should the Cloning of Human Beings Be Prohibited?
Viewpoint:
Yes, because of the potential physical dangers and the profound ethical
dilemmas it poses, the cloning of human beings should be prohibited.

Viewpoint:
No, the cloning of human beings should not be prohibited because the
potential for medical accidents or malfeasance is grossly overstated,
and the ethical questions raised by detractors are not unique to
cloning—indeed, ethical questions attend every scientific advancement.
Since
the birth of Dolly, the cloned sheep, in 1997, several reproductive
scientists, including Severino Antinori, Brigitte Boisselier, and
Panayiotis Michael Zavos, have announced that they were ready to clone
human beings. However, cloning mammals is still a highly experimental
technique. Scientists involved in cloning various mammals have reported
many technical problems. A large majority of the clones die during
gestation or soon after birth. Placental malfunction seems to be a
major cause of death. Many of the surviving clones are plagued with
serious physiological and genetic problems. During embryological
development, cloned sheep, cows, pigs, and mice tend to become
unusually large. Clones are often born with a condition called "large
offspring syndrome," as well as severe respiratory and circulatory
defects, malformations of the brain or kidneys, or immune dysfunction.
It is not yet known whether clones will develop and age normally, or
whether subtle failures in genomic reprogramming or genetic imprinting
might lead to various defects. Many scientists believe that, at least
in the near future, experiments in human cloning would involve many
failures, miscarriages, stillbirths, and the birth of deformed babies.
Some observers think that the reckless claims made by some scientists
stimulated the passage of premature Congressional legislation that
would ban all human cloning, both reproductive and therapeutic
(non-reproductive). Similar reactions have occurred in other nations.
For example, the French and German governments jointly asked the United
Nations to call for a world.....

Conclusion
The cloning of
animals could result in considerable economic benefits. Every effort
should be made, however, to preserve the original genetic diversity by
maintaining at least small herds of the original donors. Cloning of
humans, on the other hand, including research directed towards that
end, is totally unacceptable and must be prohibited by law. Just
recently nineteen countries from Europe, Scandinavia, and the Near East
signed an agreement to prohibit human cloning. It has
been
announced that a proposal for an emergency prohibition on the cloning
of humans will be introduced in the U.S. Congress in the session
beginning in January 1998. In response to the claim by a physicist that
he will soon initiate research on human cloning, the Federal Food and
Drug Administration warned that this agency will shut down any such
efforts that are without its permission. It should be clear that with
human cloning vital interests rest not on any potential
successes, but on its certain failures.
The as yet unsuccessful attempts to correct genetic diseases (such as
hemophilia) through genetic manipulation will be discussed in a future
article. Also to be covered are the successful production of human
proteins in the milk of pigs, cows, and sheep, as well as the
introduction of beneficial changes in plants by genetic manipulation.
It must be borne in mind that all such genetic manipulations merely use
what God has produced and are limited by the fact that genetic systems
are incredibly complex and are difficult to manipulate without
producing harmful and even lethal results. We can repair defective
genetic systems, but we cannot improve a normal, healthy genetic
system.
The question is often asked, would a human clone have a
soul? Absolutely. Occasionally some people are troubled by the assumed
possibility that human manipulation will present a problem too hard for
God to solve. But with God nothing is impossible. He is always far
ahead and above anything man may do. In fact, I am a clone, just as is
true of all others who have identical twins. I am certain that both my
twin brother and I have a God-given soul.

Resources
1-http://science.howstuffworks.com/cloning1.htm
http://www.bookrags.com/research/should-the-cloning-of-human-beings--sind-01/
http://www.bookrags.com/research/human-cloning-wog/

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رد: cloning للصف الثالث ثنوي علمي تقرير

مُساهمة من طرف عاشق الشفايف الحمر في السبت مارس 29, 2008 12:52 pm

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رد: cloning للصف الثالث ثنوي علمي تقرير

مُساهمة من طرف ساحرة البشر في الإثنين مارس 31, 2008 2:01 pm

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رد: cloning للصف الثالث ثنوي علمي تقرير

مُساهمة من طرف medokkh في الأربعاء أبريل 02, 2008 7:18 pm

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رد: cloning للصف الثالث ثنوي علمي تقرير

مُساهمة من طرف زائر في الإثنين سبتمبر 08, 2008 11:19 pm

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