Cloning

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Introduction

Cloning is a topic that is now very current. There are many different questions, but also the same number of answers.

Is it really right to clone a sheep? Some would say Yes. Others No. And a more important question: Should we clone humans? The answers to these questions would probably be: Yes, of course, No absolutely not, Maybe. All answers have both advantages and disadvantages.
Who should decide? The Scientists? EU? FN? Maybe USA?
Today, it’s illegal to clone humans, but not to research in the subject.
I think that many things are going to happen in the next few years within this hesitating subject.

Cloning, what is it?
When you clone an animal, you take cells from an animal’s tissue. In these cells there are genetic information. These cells are taken to a laboratory for breeding. When they have multiplied, you take an egg-cell from another animal, as a suggestion one from the same species, and take away the genetic information in its cells and replace it with the information from the first animal.
Now we have the second animal which has an egg-cell, with the genetic information from the first animal. Then, the eggs are treated and can develop to embryos in a laboratory. The embryos are then operated into a third animal’s uterus. The third animal will now give birth to a young which is a genetical copy of the first animal. Now you have cloning.

Already in the 1970s scientists succeeded to clone frogs, but they didn’t survive more than a couple of days. In February 1996 the big news that scientists had succeeded to clone a mammal came and shook the world. It was the English sheep Dolly.

Clones
A group of organisms which all derive from one single individual through asexual reproduction, are known as clones. All members of a clone are genetically identical, except for changes in the hereditary material that may occur by mutation.
In 1993, scientists made experiments in “in vitro fertilization” of human eggs.
(When you use IVF, eggs are taken from the woman’s body, then they are fertilized in a laboratory with her partner’s sperm. The resulting embryos are transferred back to her uterus usually within 2-6 days.) This led to the cloning of human embryos by dividing in vitro fertilized eggs at a very early stage. Though this method produces a twin rather than a clone.
In 1997, experiments in cloning led to the development of a sheep from a cell of an existing animal. Since 1997, many mice and cows have also been cloned.
Because of the scientists having succeeded in cloning these mammals, many ethical questions have come up, concerning the possibility of cloning humans.

How alike does the clones get, compared to its original?
The clones can’t take over the thoughts of the original. The memory of a creature is not in the hereditary material that you copy when you clone something. A clone develops its own memories and its own personality. A clone has exactly the same genes as the original. That is also the one and only thing they have in common. We can look at twins for an example. They also have the same genes, but already under the development of the embryo, the two twins develop differently depending on microscopic changes in the environment of the uterus. Their brains are also extremely different. And that’s how it is with clones too.
Clones would probably differ even more from each other, because they probably came from different uteruses.

In some experiments, scientists have seen that the clones can differ in the appearance from the original. Because of a vibrating movement that occurs during cloning. In these experiments, scientists observed mice with different types of fur colour.
You can almost say that a clone is the original’s younger twinbrother.
Researchers have studied twins who have grown up apart from each other and then compared them.

Then you could find a connection between their personality characteristics, intelligence and the risk of having the same mental diseases. Only 25 % of twins and clones are quite alike each other, the remaining 75 % are totally different from each other, no matter what their heredity material is. Clones will develop to completely independent individuals with characteristics which the original doesn’t have.

How Scientists Clone Cells
In the beginning when cloning was new, scientists made cloned cells in their laboratory by letting a single cell divide into a population of genetically identical cells. In this process, the original cell was put in a laboratory dish, containing culture medium (nutrients needed to keep a cell alive).
The cell’s natural process of mitosis (cell division) then started to produce genetically identical offspring. This process shows how cells multiply, for instance, in plants and in the human body.

Later on, scientists started to develop more complicated cloning techniques by using animal embryos. Every cell in an animal are created from a fertilized egg. The fertilized egg divides to form an embryo, and each cell in the embryo has the same genetic material. At some point in the embryo’s growth and development, the cells are treated differently and each one becomes special. For instance, a heart cell only functions in the heart and not the liver, even though the genes of a heart cell and liver cell are the same.

Scientists began to experiment with embryo cells that were undifferentiated, in the 1950s. Undifferentiated means that they were not yet specialized into a particular type of cell.

Scientists found out that such embryo cells are totipotent (they are able to give rise to all the different cell types in the body). Scientists made use of this characteristic, and developed three different techniques to clone embryo cells: blastomere separation, blastocyst division, and somatic cell nuclear transfer.

Blastomere Separation
In blastomere separation, scientists fertilize an egg cell with a sperm cell in a laboratory dish. The embryo is now allowed to divide itself, until it forms a mass of about four cells. After that, the outer layer of the embryo is removed and placed in a special solution that causes the individual cells of the embryo, which are known as blastomeres, to separate. Then each blastomere is set in culture, where it forms an embryo containing the same genetic makeup as the original embryo. Each new embryo can then be implanted into the uterus of a surrogate mother to develop during a normal pregnancy.

Blastocyst Division
In blastocyst division, scientists allow a fertilized egg to divide until it forms a mass of about 32 to 150 cells, known as a blastocyst. After that the blastocyst is split in two parts and then both parts are implanted into the uterus of a surrogate mother. The two halves develop as identical twins.

Somatic Cell Nuclear Transfer
While blastomere separation and blastocyst division produce animals containing the genetic material from both parents, somatic cell nuclear transfer produces an animal that carries the genetic material of only one parent.

When this technique is used, scientists takes the genetic material from a donor’s somatic cell (any body cell other than an egg or sperm cell) and places it in an enucleated egg cell which means an egg cell with its nucleus, and almost all of its genetic material, removed. The cloned cell that is left, contains the genetic material of the donor’s somatic cell. Scientists combine the somatic cell and enucleated egg cell by using fusion or injection.

If you use the fusion method, scientists place a somatic cell right next to an enucleated egg cell so that they touch each other. An electric pulse which are applied to the two cells pushes the somatic cell’s nucleus into the enucleated egg cell. By using the injection method, scientists inject the somatic cell’s nucleus directly into the enucleated egg cell.

Dolly the sheep
The sheep Dolly was the first adult mammal to be cloned. The researchers, led by Ian Wilmut at the Roslin-institution in Edinburgh achieved this success in 1996. Dolly is a unique clone because she was made of one single cell, (you usually use several ones.) The cell’s nucleus came, in this case, from a 6 years old ewe’s udder. Then, scientists took an eggcell from another sheep, where the nucleus was gone, after that, the ordinary cell was melted with the eggcell. After that, it was placed in a third sheep, so called the surrogate mother. This technique is not flawless, Ian Wilmut had to do 277 attempts before he succeeded with Dolly.

Early farmers and Genetic engineering
Thousands of years ago, farmers started to clone plants in simple ways. They took a cutting of a plant and let it root to make another plant.
The early farmers also came up with breeding techniques to reproduce plants with such characteristics as faster growth, larger seeds, sweeter fruits etc. By combining these breeding techniques with cloning, they were able to produce many plants with desired traits.
These first forms of cloning and breeding were very slow and sometimes they were even unpredictable.

In the late 1900s scientists developed genetic engineering, which enabled humans to eliminate undesirable characteristics or to produce desirable new ones, in an organism´s genetic or hereditary material. Genetic engineering is when you manipulate deoxyribonucleic acid, (DNA), the genetic material of all living things. Today, scientists use genetic engineering and cloning together to quickly and cheap produce thousands of plants with desired characteristics.

History of cloning
The laboratory cloning technique when you used embryo cells that were not held together,
were first developed in the late 1800s. This was when a German zoologist named Hans Dreisch separated a sea urchin embryo when it was only two cells. He succeeded and both cells grew up to adults.

In the early 1900s, the German embryologist Hans Spemann tried Dreisch’s work on salamanders, he succeeded. In his experiments, Spemann found out that a nucleus from a salamander embryo cell could show the way for the development of a complete organism.
In 1938, he published his results and suggested a “fantastical” experiment which was to produce an animal by removing the nucleus from one cell and placing it into an egg cell with its nucleus removed.

1962 - John Gurdon claimed that he had cloned frogs from adult cells.
1963 - J.B.S. Haldane coined the term ´clone.´
1966 - The complete genetic code was established.
1969 - Shapiero and Beckwith isolated the first gene.
1970 - First restriction enzyme was isolated.
1972 - Paul Berg created the first recombinant DNA molecules.
1973 - Cohen and Boyer created the first recombinant DNA organisms.
1977 - Karl Illmensee claimed to have created mice with only one parent.
1979 - Karl Illmensee claimed that he had cloned three mice.
1983 - Kary B. Mullis developed a polymerase chain reaction technique for rapid DNA synthesis.
1983 - Solter and McGrath fused a mouse embryo cell with an egg without a nucleus, but failed to clone using their technique.
1984 - Steen Willadsen cloned sheep from embryo cells
1985 - Steen Willadsen cloned sheep from embryo cells. Steen Willadsen joined Grenad Genetics to commercially clone cattle.
1986 - Steen Willadsen cloned cattle from differentiated cells.
1986 - First, Prather, and Eyestone cloned a cow from embryo cells.
1990 - Human Genome Project began.
1996 - Dolly, the first mammal was cloned from adult cells.
1997 - President Bill Clinton proposed a five year moratorium on cloning.
1997 - Richard Seed announced his plans to clone a human.
1998 - Teruhiko Wakayama created three generations of genetically identical cloned mice.
2000: Pigs and goats reported cloned from adult cells. Britain became the first country to grant a patent for cloned early-stage human embryos.
March 2000: Scientists announced first cloned pigs.
2001: An endangered Asian ox died two days after the birth of an ordinary disease after it was cloned and gestated in the womb of a cow. Advanced Cell Technology of Worcester, Massachusetts, said it produced a six-cell cloned human embryo, in research aimed at harvesting stem cells.
2002: Rabbits and a kitten reported cloned from adult cells.
December 26, 2002: Clonaid claimed to have produced the first human clone, a baby girl called Eve.

Can Humans Be Cloned?
We all know that scientists can clone animals, but can they clone humans? In 1998 a Korean research team said that they had cloned a human embryo through somatic cell nuclear transfer.
This time, the embryo only survived to four cells. On November 25,2001 researchers at the biotechnology firm Advanced Cell Technology claimed that they had cloned human embryos that divided to six cells before dying. The announcement that “Advances Cell Technology” made, brought strong critics from the Vatican as well as political leaders, including U.S. president Bush.
Many scientists don’t think that these embryos should be considered as human embryos. That’s because the embryos from the two experiments didn’t double their cell size every 24 hours.
In any case, scientists feel that it’s only a matter of time before they can solve the technical difficulties of human cloning.

Religious opinions
The Vatican thinks that cloning violates the Catholic teaching that life begins with conception and that it shows a disrespect towards humanity.
Researchers defended the development of cloning by saying that they wanted to harvest stem cells rather than to create babies. Many scientists think that stem cells can be used to cure lots of diseases, including diabetes, strokes, cancer, AIDS, neurodegenerative disorders such as Parkinson’s and Alzheimer’s disease etc.

Summary
Cloning is when you create a ... Ladda upp arbete

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Daniel Svensson [2003-04-12]   Cloning
Mimers Brunn [Online]. http://mimersbrunn.se/article?id=1976 [2017-04-26]

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