Math Science Chemistry Economics Biology News Search
Although many scientists have succeeded in cloning animals up to now, the word clone was invented in 1963 by the British biologist J.B.S. Haldane as the biological possibilities for the human species of the next ten thousands years. Of course, cloning requires knowledge in the genetic field.
In 1902, Walter Sutton proved that chromosomes hold the genetic information, and in the same year, Hans Spemann announced that this genetic information is used to create a new organism. He also performed the first nuclear transfer experiment in 1928 and developed the first basic method, later used for cloning, by transfering one cell’s nucleus into an egg (without a nucleus). In 1952, using this method, two scientists, Briggs and King, cloned tadpoles. Ten years later, John Gurdon, from the Oxford University declared he had cloned South African frogs, using fully differentiated adult intestinal cells. As it was the beginning of cloning, a lot of scientists remained skeptical and began to find flaws in his work. But genetic knowledge evolved and soon, the complete genetic code was established in 1966 and paved the way to the explosion of genetic engineering studies. The DNA double-helix structure was discovered in 1962 after 10 years of research by James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin. The first gene (small sequence of nucleotides) was isolated in 1969 by James Shapiro of Harvard University and Jonathan Beckwith (this gene controls the digestion of sugar in a bacterium). But everything changed when the first restriction enzyme, called ColE1, was isolated in 1970. This enzyme, quickly followed by a number of others with different sequence specificities, is used to cut DNA at precise and specific locations: this ability led to the further manipulation of DNA. All those genetic discoveries were then used to find drugs for illnesses, new sources of energy such as biofuel, to create plants that can resist to insects and also developed the cloning techniques.
Almost 30 years after Briggs and King, the German biologist Karl Illmensee announced he had cloned the first mammal (3 mice in 1979) with a single parent by transferring the nucleus of a mouse’s cell into mouse eggs. It was very surprising because this announcement came after several failed cloning experimentations that were beginning to convince scientists that cloning mammals was impossible. They tried to do as well as Illmensee had done but they were unable to reproduce his results. They later discovered the results were fake. We have to wait until 1996 for the birth of the first real cloned mammal, a sheep called Dolly, thanks to Ian Wilmut, from the Roslin Institute in Scotland, who, at the same time, found out that the genetic information of a cell does not diminish as the cell divides and DNA returns to its original state at every division. Polly, another lamb cloned was created one year later from skin cells genetically altered to contain a human gene in every cell of its body. Later on, mice and cows were cloned by Japanese using the same technique.
But the birth of cloned mammal led to a worldwide debate on cloning ethics and US President William Bill Clinton proposed a legislation to forbid human cloning for at least five years and this ban was signed by nineteen European nations and thousands of biologists and physicians. Signed in 1997, this five year moratorium ended in 2002 but no cloned human has been officially born.