Cloning
Cloning is the process of creating an identical copy of an original organism or thing. A cloning in the biological sense, therefore, is a molecule, 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 is asexually reproduced by chance (as with identical twins), but in common parlance, a clone is an identical copy created intentionally.
The term clone is derived from κλων, the Greek word for "twig". In horticulture, the spelling clon was used until the twentieth century; the final e came into use to indicate the vowel is a "long o" instead of a "short o". Since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively
The possibility of human cloning, raised when Scottish scientists at Roslin Institute created the much-celebrated sheep "Dolly" , aroused worldwide interest and concern because of its scientific and ethical implications. The feat, cited by Science magazine as the breakthrough of 1997, also generated uncertainty over the meaning of "cloning" --an umbrella term traditionally used by scientists to describe different processes for manuplicating biological material
History of Cloning
It seems that every week, newspapers report on new advances in the science of cloning. Everybody knows about Dolly the cloned sheep, but few people know all the details about cloning, including the fact that scientists have been working on it for over 100 years.
Cloning in Nature
Cloning has been going on in the natural world for thousands of years. A clone is simply one living thing made from another, leading to two organisms with the same set of genes. In that sense, identical twins are clones, because they have identical DNA. Sometimes, plants are self-pollinated, producing seeds and eventually more plants with the same genetic code. Some forests are made entirely of trees originating from one single plant; the original tree spread its roots, which later sprouted new trees. When earthworms are cut in half, they regenerate the missing parts of their bodies, leading to two worms with the same set of genes. However, the ability to intentionally create a clone in the animal kingdom by working on the cellular level is a very recent development.
Early Progress
The first cloned animals were created by Hans Dreisch in the late 1800's. Dreich's original goal was not to create identical animals, but to prove that genetic material is not lost during cell division. Dreich's experiments involved sea urchins, which he picked because they have large embryo cells, and grow independently of their mothers. Dreich took a 2 celled embryo of a sea urchin and shook it in a beaker full of sea water until the two cells separated. Each grew independently, and formed a separate, whole sea urchin.
In 1902, another scientist, embryologist Hans Spemman, used a hair from his infant son as a knife to separate a 2-celled embryo of a salamander, which also grow externally. He later separated a single cell from a 16-celled embryo. In these experiments, both the large and the small embryos developed into identical adult salamanders. Spemman went on to propose what he called a "fantastical experiment" -- to remove the genetic material from an adult cell, and use it to grow another adult. In this way, he theorized, he would be able to prove that no genetic material was lost as cells grew and divided.
New Advances
There were no major advances in cloning until November of 1951, when a team of scientists in Philadelphia working at the lab of Robert Briggs cloned a frog embryo. This team did not simply break off a cell from an embryo, however. They took the nucleus out of a frog embryo cell and used it to replace the nucleus of an unfertilized frog egg cell, completing the "fantastical experiment" of nearly 50 years before. Once the egg cell detected that it had a full set of chromosomes, it began to divide and grow. This was the first time that this process, called nuclear transplant, was ever used, and it continues to be used today, although the method has changed slightly.
 In 1962, biologist John Gurdon of Oxford University announced that he had used the nucleus of fully differentiated adult intestinal cells to clone South African frogs. Gurdon's results electrified the scientific community, but some scientists remained skeptical and began to find flaws in his work.
 In 1963, the British biologist J.B.S. Haldane is credited to have coined the term "clone" in a speech entitled "Biological Possibilities for the Human Species of the Next Ten-Thousand Years." Even though many scientists had described, and even completed the cloning process by this time, the term "cloning" had never been used to describe such experiments.
 In 1966, Marshall Niremberg, Heinrich Mathaei, and Severo Ochoa crack the genetic code. The cracking of the genetic code opened the door for the explosion of genetic engineering studies and achievements beginning in the late 1970's.
 In 1967, the enzyme DNA ligase was isolated. DNA ligase binds together strands of DNA. Its discovery, with the isolation of the first restriction enzyme 1970, paved the way for the first recombinant DNA molecules to be created by Paul Berg in 1972. In the recombinant DNA process, ligase bonds the "sticky" ends of complimentary DNA strands previously cut by a restriction enzyme.
 In 1969, James Shapiero of Harvard University, working with Johnathan Beckwith announce that they had isolated the first gene. The gene directed the digestion of sugar in a certain type of bacteria. Shapiero and Beckwith's discovery part of a wave of molecular biology discoveries directly following the 1966 cracking of the genetic code. The announcement also increased the public's concern about the growing power of molecular biologists.
 In 1970, both Howard Temin and David Baltimore, working independently, isolated the first restriction enzyme. The restriction enzyme, called Reverse Transcriptase, cut DNA molecules at precise locations. This capability led to the future manipulation of DNA.
 In 1972, Paul Berg of Stanford University created the first recombinant DNA molecules by combining the DNA of two different organisms.
 In 1973, Stanley Cohen and Herbert Boyer created the first recombinant DNA organism using recombinant DNA techniques pioneered a year earlier by Paul Berg. Recombinant DNA, also called gene splicing, is a technique that allows scientists to manipulate the DNA of an organism.
 In 1977, a German scientist shocked the world, claiming to have cloned three mice from embryos. Although embryos had been cloned before, no one had been able to do the experiment with mice because the cells were so small and the tools so large that the cells were traumatized and would eventually die after a few divisions. He instantly became famous, telling the world how he cloned his mice. However, he refused to actually demonstrate any of his techniques, and when other scientists couldn't replicate his work, he came under suspicion. He was challenged -- repeat his work or be discredited. He accepted.
He claimed to work nights and mornings when no one was around, but the equipment was never disturbed. He showed off his mouse embryos' growth daily, even though a malfunction in the water purification system left other scientists at his lab unable to grow other embryos. Later, in his cabinet, test tubes were found with mouse embryos in them, each at a different stage of development. Most scientists do not believe that this scientist was ever able to clone adult mice.

 In 1978, a science fiction writer published a book claiming that a millionaire (known to the readers only as Max) had come to him because of his connections as a writer, and asked the him to arrange for Max to be cloned. The author eventually agreed, as the story goes, and Max was cloned. The book was ranked in the Top 10 list of popular books. Scientists who read his book, however, noticed discrepancies between the book and scientific data. One man who was quoted in the book was angry enough to sue. The publisher admitted that the book was a hoax, but the author maintains his claim to this day.
Within these two years, two front-page advances in cloning were discovered to be, most likely, frauds. As a direct result, many scientists began to claim that cloning of mammals was impossible. Funding and interest dropped, and cloning returned to the realm of science fiction for several years.
 In 1979, One of the most surprising of modern genetics announcements was made, Karl Illmensee claimed to have cloned three mice The announcement came at a time where a succession of failed cloning attempts were beginning to convince biologists that the cloning of a mammal was impossible.
 In 1983, In what has been called by some the greatest achievement of modern molecular biology, Kary B. Mullis developed the polymerase chain reaction (PCR) in 1983. PCR allows the rapid synthesis of designated fragments of DNA. Using the technique, over one billion copies can be synthesized in a matter of hours.
 In 1983 Davor Solter, working with David McGrath, attempted to clone mice using his own version of the nuclear transfer method. They wanted to use the cloning experiment to determine if DNA specializes as a cell specializes.
 In 1984, Danish scientist Steen Willadsen succeeded in cloning a sheep from embryo cells. His work was the first verified cloning of a mammal using the method of nuclear transfer.
 In 1985 Steen Willadsen, the first to clone a farm animal using the nuclear transfer method, joined Grenada Genetics, a bioengineering company. Willadsen used his cloning technique to duplicate the embryos of prize cattle. Grenada Genetics saw the profitability of the future cattle cloning industry. Top breed cattle embryos were highly desired by farmers, Willadsen's procedure mass produced identical copies of such embryos.
 In 1986, while working at Grenada Genetics, Steen Willadsen cloned a cow using differentiated, one week old embryo cells. The work proved that the genetic information of a cell did not diminish as a cell specialized and that DNA could return to its original state. Willadsen never officially published his results, but the work was a strong influence in Ian Wilmut's decision to attempt to clone from adult cells, which he accomplished in the famous 1996 birth of "Dolly.”
 In October of 1990, the National Institutes of Health officially began the Human Genome Project, a massive international collaborative effort to locate the 50,000 to 100,000 genes and sequence the estimated 3 billion nucleotides making up the entire human genome. By determining the complete genetic sequence, scientists hope to begin correlating human traits with certain genes. With this information, medical researchers have begun to determine the intricacies of human gene function, including the source of genetic disorders and diseases that have plagued medical researchers for years.
 In July 1995, Ian Wilmut and Keith Campbell of the Roslin Institute in Scotland successfully cloned two sheep, named Megan and Morag, from differentiated embryo cells. The idea to clone sheep was arrived at by Ian Wilmut as an answer to a gene insertion project he was researching. At the time, time inserting genes into embryo cells was a difficult and tedious process. Few embryos survived the insertion of a gene, even fewer incorporated the gene into their genetic code, and even fewer organisms developed properly and used the gene in all of their cells.
 On July 5, 1996, Dolly, the first organism ever to be cloned from adult cells, was born. Ian Wilmut and Keith Campbell, researchers at the Roslin Institute in Scotland created Dolly using a technique similar to that with which they created the first sheep from differentiated embryo cells in 1995.
 On March 4, 1997, President Clinton, in response to the large scale human cloning ethics debate brought about by Ian Wilmut's announcement of the creation of Dolly, proposed a five year moratorium on federal and privately funded human cloning research. In addition to this proposal, Clinton asked the National Bioethics Advisory Commission to review the prospects of human cloning and determine if legal preventive actions should be taken.
 On December 5, 1997, Harvard graduate Richard Seed announced that he planned to clone a human being before any federal laws could be enacted to ban the process. Seed's announcement added fuel to the raging ethical debate on human cloning that had been sparked by Ian Wilmut's creation of Dolly, the first clone obtained from adult cells.
 In July 1997, building upon their success of the creation of Dolly, the first animal cloned from adult cells, Ian Wilmut and Keith Campbell created Polly, a Poll Dorset lamb cloned from skin cells grown in a lab and genetically altered to contain a human gene. Polly's birth signified the first step in the application of cloning technology to the production of a useful product. Most scientists believe that most beneficial application of cloning will come from the exact reproduction of animals genetically altered to produce human proteins or organs more easily accepted in transplants. Wilmut and Campbell's creation of Polly surprised the scientific community by how fast cloning technology was progressing. The cloning of genetically altered farm animals was not expected for another five years.
In July 1998, Ryuzo Yanagimachi, Toni Perry, and Teruhiko Wakayama of the University of Hawaii announced that they had cloned fifty mice from adult cells since October of 1997. The new cloning technique, which has proven to be more efficient than that performed by Ian Wilmut in his cloning of Dolly, was developed by postdoctoral student Wakayama in his spare time.

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