Referat Cloning
Mai jos puteti citi fragmente din
Referat Cloning si de asemenea puteti face
Download Referat CloningCiteste fragmente din Referat Cloning
Cloning
Cloning is a very controversial theme. It is considered by many people
and nations as an immoral practice, a bad appendix of science. Cloning
does violate the laws of nature, because we are the ones that manipulate
it. It interferes with the natural and common reproduction. But we have
to consider another point of view. What will happen to the people who
can t procreate by the traditional way, nature s way? Don t they have
the same rights with us to become happy, to fulfill their wishes of
becoming a father or a mother? How can we stop people from practicing
the universal right of searching for happiness? If we do it, we would be
selfish. That s why cloning could be a solution to that dilemma.
We should proceed this debate with the history of cloning. The modern
era of laboratory cloning began in 1958 when F.C. Steward cloned carrot
plants from mature single cells placed in a nutrient culture containing
hormones. The first cloning of animal cells took place in 1964. John B.
Gurdon took the nuclei from tadpoles and injected them into unfertilized
eggs. The nuclei containing the original parents genetic information
had been destroyed with ultraviolet light. When the eggs were incubated,
Gurdon discovered that only 1% to 2% of the eggs had developed into
fertile adult toads. The first successful cloning of mammal was achieved
nearly twenty years later. Scientists from Switzerland and the U.S
successfully cloned mice using a method similar to Gurdon s. In 1993 the
first human embryos were cloned using a technique that placed individual
embryonic cells in a nutrient culture where the cells then divided into
48 new embryos. These fertilized eggs did not develop to a stage that
could be used for transplantation into a human uterus.
WHAT IS CLONING?
Cloning is the creation of an organism that is an exact copy of
another. There are different types of cloning. A basic understanding of
the different types of is the key to taking an informed stance on
current public policy issues and making the best personal decisions.
WHAT IS A CLONE?
As per biology, a clone is a cell or an organism that is genetically
identical to another cell or organism. Many simple organisms such as
bacteria reproduce themselves by copying their DNA and splitting in
half. The two bacteria that result from this form of asexual
reproduction are genetically similar, they are clones of each other. In
contrast, during the process of sexual reproduction, the nucleus of a
sperm cell, which carries the father s DNA, fuses with the nucleus of an
egg cell, which contains the mother s DNA. The resulting offspring carry
genetic material from both parents and are not identical to either
parent.
The verb to clone refers to the process of creating cloned cells or
organisms. The process differs, depending on the kinds of cells used in
the cloning procedure and the desired result. Usually, when scientists
clone an animal, they take the nucleus of a cell (which contains
chromosomes made of deoxyribonucleic acid-DNA and proteins) and place it
into an egg cell (also called oocyte) from which the nucleus had been
removed. The egg cell then divides to produce an embryo that develops
into an animal, if the procedures work as planned.
WHAT IS HUMAN CLONING?
A "human clone" is a time-delayed identical twin of another person. A
clone is not an exact replica of the original, but just a much younger
identical twin. As with identical twins, the clone and the original
being will have different set of fingerprints. Ever since Dolly s (the
cloned sheep) birth in 1997 shocked an unexpecting world, Governments
have been busy trying to prevent the advent of human cloning.
There is also the fear that someone would create armies of soldiers or
even produce large amounts of workers. This could create lower class for
clones and compromising individualities.
A "black market" of fetuses could arise from desirable donors that will
want to clone themselves, i.e.: athletes, film stars, scientists and
others.
Technology is not fully developed. It has a low fertility rate. In
cloning Dolly, 277 eggs were used, 30 started to divide, 9 induced
pregnancy, and only one survived to term (Nash).
Clones may be treated as second-class citizens. Human cloning would
bring grave risks of abuses to human dignity and exploitation by
unscrupulous people.
Unknown psychosocial harms with impacts on the family and society. Many
see this as a violation of the uniqueness of a human life, which God has
given to each of us and to no one else.
WHAT IS CLONING? ARE THERE DIFFERENT TYPES 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. A basic
understanding of the different types of cloning is the key to taking an
informed stance on current public policy issues and making the best
possible personal decisions. The following three types of cloning will
be discussed: (1) recombinant DNA technology or DNA cloning, (2)
reproductive cloning, and (3) therapeutic cloning.
(1) Recombinant DNA Technology or DNA Cloning
The terms "recombinant DNA technology", "DNA cloning", "molecular
cloning" or "gene cloning" all refer to the same process the transfer of
DNA fragment of interest from one organism to a self-replicating genetic
element such as a bacterial plasmid. The DNA of interest 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.
Scientists studying a particular gene often use bacterial plasmids to
generate multiple copies of the same gene. Plasmids are self-replicating
extra-chromosomal circular DNA molecules, distinct from the normal
bacterial genome. Plasmids and other types of cloning vectors are used
by Human Genome Project researchers to copy genes and other pieces of
chromosomes to generate enough identical material for further study.
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 reduced along
with the host cell DNA. Bacteria are most often used as the host cells
for recombinant DNA molecules but yeast and mammalian cells are also
used.
(2) Reproductive Cloning
Reproductive cloning is a technology used to generate an animal that
has the same unclear DNA as another currently or previously existing
animal. Dolly was created by reproductive cloning technology. In a
process called "somatic cell nuclear transfer" (SCNT), scientists
transfer genetic material from the nucleus of a donor adult cell to an
egg whose nucleus, and thus its genetic material has been removed. The
reconstructed egg containing the DNA from a donor cell must be treated
with chemicals or electric current in order to stimulate cell division.
Once the cloned embryo reaches a suitable stage, it is transferred to
the uterus of a female host where it continues to develop until birth.
Dolly or any another animal created using nuclear transfer technology
is not truly an identical clone of the donor animal. Only the clone s
chromosomal or nuclear DNA is the same as the donor. Some of the clone s
genetic materials come from the mitochondria in the cytoplasm of the
enucleated egg. Mitochondria, which are organelles that serve as power
sources to the cell, containing their own short segments of DNA.
Acquired mutations in mitochondrial DNA are believed to play an
important role in the aging process.
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.
(3) Therapeutic Cloning
Therapeutic cloning, also called "embryo cloning", is the production of
human embryos for use in research. The goal of these processes 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. Stem cells are
important to biomedical researchers because they can be used to generate
virtually any type of specialized cell in the human body. Stem cells are
extracted from the egg after it has divided for 5 days. The egg at this
stage of development is called a blatocyst. The extraction process
destroys the embryo, which raises a variety of ethical concerns. Many
researchers hope that one day stem cells can be used to serve as
replacement cells to treat heart disease, Alzheimer s, cancer, and other
diseases.
In November 2001, scientists from Advanced Cell Technologies (ACT), a
biotechnology company in Massachusetts, announced that they had cloned
the first human embryos for the purpose of advancing therapeutic
research. To do this, they collected eggs from women s ovaries and then
removed the genetic material from these eggs with a needle less than
2/10,000th of an inch wide. A skin cell was inserted inside the
enucleated egg to serve as a new nucleus. The egg began to divide after
it was stimulated with a chemical called ionomycin. The results were
limited in success. Although this process was carried out with eight
eggs, only three began dividing, and only one was able to divide into
six cells before stopping.
Pros:
ORGANS COULD BE CLONED FOR USE IN TRANSPLANTS
Scientists hope that one day therapeutic cloning can be used to
generate tissues and organs for transplants. To do this, DNA would be
extracted from the person in need of a transplant and inserted into a
nucleated egg. After the egg containing the patient s DNA starts to
divide, embryonic stem cells can be transformed into any type of tissue
would be harvested. The stem cells would be used to generate an organ
tissue that is a genetic match to the recipient. In theory, the cloned
organ could than be transplanted into the patient without the risk of
tissue rejection. If organs could be generated from cloned human
embryos, the need for organ donation could be significantly reduced.
HUMANS COULD BE CLONED IN ORDER TO ALLOW AN INFERTILE COUPLE TO HAVE A
CHILD
The Italian doctor Secerino Atinori wants to offer cloning as a
treatment for infertility. Critics have pointed out that anyone who was
a clone of their parents would be under unknown psychological pressures
throughout their childhood. Would they feel they were living up the
achievements of their "original"? And how would a woman feel about
bringing up a much younger version of the person she fell in love with?
HUMANS COULD BE CLONED IN ORDER TO BRING BACK A CHILD KILLED IN AN
ACCIDENT
In recent years, some bereaved families have contacted scientists
asking them to clone a dead child. However, even if human cloning was
possible, families might be distraught to discover their new baby was
not exactly like their dead older brother or sister- and the
replacement child might suffer feelings of inferiority about being
born purely to take the place of their dead sibling.
HUMANS COULD CE CLONED TO REPLICATE THE TALENTS OF EXCEPTIONAL HUMAN
BEINGS
If Mother Theresa or Einstein could be genetically reproduced, their
clones might choose very different paths in life, and disappoint the
people who had chosen to create them.
Cloning could do many good things for our wildlife and our economy. The
process of cloning can save us a lot of money. A crop that is imported
in our country could instead be cloned here. It would also make the
product cheaper. Cloning would also develop stronger plants, resistant
to disease, parasites, and insect damage. With better plants, cloning
could lead to more profit for farmers and we could clone an abundance of
trees, which would help the ecological health of our planet. Cloning is
good for us as a nation and a world, to save many different types of
endangered species. We would also be able to keep an animal within a
controlled number.
Cons:
THE RISKS OF CLONING:
Reproductive cloning is expensive and highly inefficient. More than 90%
of cloning attempts fail to produce viable offspring. More than 100
nuclear transfer procedures could be required to produce one viable
clone. In addition to low success rates, cloned animals tend to have
more compromised immune function and higher rates of infection, tumor
growth, and other disorders. Japanese studies have shown that cloned
mice live in poor health and die early. Many cloned animals have not
lived long enough to generate good data about how clones age. Appearing
healthy at a young age unfortunately is not a good indicator of long
term survival. Clones have been known to die mysteriously. For example,
Australia s first cloned sheep appeared healthy and energetic on the day
she died, and the results from her autopsy failed to determine the cause
of her death.
Cloning destroys the genetic diversity of life. When everything is the
same genetically then it is more likely that the entire population will
be wiped out by their disease or predator. Iam Wilmut, a researcher in
Roslin, Scotland says: "The more you interfere with reproduction, the
more danger there is of things going wrong".
SHOULD HUMANS BE CLONED?
Due to the inefficiency of human cloning 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 problem 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 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.
WHAT DO YOU THINK ABOUT THIS? IS CLONING ETHICAL? THAT IS A QUESTION
THAT WILL BE WITH US FOR A LONG TIME. ARE THERE BENEFITS OF CLONING? THE
ANSWER IS A RESOUNDING YES. IS THERE A BAD SIDE OF CLONING? THIS IS
ANOTHER IRREFUTABLE AFFIRMATIVE. SHOULD WE CLONE? DO BENEFITS OF HUMAN
CLONING OUTWEIGHT THE COSTS OF OUR DIGNITY?
It is your choice!!!!!!!!!!!!!!!
ì¥Â@
