History of Cloning

Cloning of plants (such as growing a plant from a cutting) has been a common practice of mankind for hundreds and perhaps thousands of years. Even cloning of small animals has a long history dated back to the 1960's. However, human cloning had not been thought possible until the successful cloning of the first mammal, Dolly the sheep, in 1997. The birth of Dolly is a major scientific and technological breakthrough. However, it also raised the possibility that one day humans will be cloned, as well as many medical and ethical issues and concerns associated with this possibility. Following the cloning of Dolly, many other animals, including cows and mice, have been successfully cloned. Though Clonaid, a human cloning company founded by the religious movement group Raelian, claimed that a clone human baby was born in December 2002, no human cloning has been scientifically confirmed thus far.

Some of the most significant events in the history of cloning are listed below:

1880's - August Weismann, professor of zoology and comparative anatomy at the University of Freiberg, proposed that the genetic information of a cell would diminish with each cell division.

1880's - Wilhelm Roux experimentally confirmed Weismann's theory. When he destroyed one cell of a 2-cell frog embryo with a hot needle, only a half-embryo developed.

1894 - Hans Dreisch experimentally challenged the theory of Weismann and Roux. Dreisch showed that blastomeres isolated from 2- and 4-cell sea urchin embryos could develop into small larvae.

1901 - Hans Spemann split a 2-cell salamander embryo into two parts, which developed into two complete organisms. This result showed that early embryo cells retain all the genetic information necessary to develop into a new organism.

1902 - Walter Sutton, in "On the Morphology of the Chromosome Group in Brachyotola magna", hypothesized that chromosomes hold the genetic information in the nucleus.

1914 - Hans Spemann performs the first successful nuclear transfer experiments.

1938 - Hans Spemann published the results of his 1928 nuclear transfer experiments. In his book "Embryonic Development and Induction", Spemann proposed a "fantastical experiment" to transfer one cell's nucleus into an egg without a nucleus, providing the basis for subsequent cloning experiments.

1962 - John Gurdon of Oxford University claimed that he had cloned South African frogs from the nucleus of fully differentiated adult intestinal cells.

1963 - The British biologist J.B.S. Haldane used the term "clone" in a speech.

1964 - F. E. Steward of Cornell University successfully grew a complete carrot plant from a fully differentiated carrot root cell. This surprising result proved that cloning from differentiated cells was possible.

1969 - James Shapiero and Johnathan Bechwith of Harvard University isolated the first gene. Their discovery added to the growing power of molecular biologists.

1972 - Paul Berg of Stanford University created the first recombinant DNA molecules.

1979 - Karl Illmensee claimed to have cloned three mice.

1983 - Kary Mullis invented the Polymerase Chain Reaction, or PCR. PCR allows the rapid replication of designated fragments of DNA. This technique greatly facilitated every aspect of molecular biology.

1984 - Danish scientist Steen Willadsen cloned a sheep from embryonic cells. This was the first confirmed case of mammalian cloning. Willadsen used a method called nuclear transfer.

1986 - Steen Willadsen, working for the biotechnology company Grenada Genetics, cloned a cow using differentiated cells extracted from one-week-old embryos.

1986 - Neal First, Randal Prather, and Willard Eyestone of the University of Wisconsin also cloned a cow from embryonic cells.

Megan and Morag
Megan and Morag
Photo courtesy the Roslin Institute

1990 - The Human Genome Project began. This international collaborative effort attempted to sequence the entire genetic makeup of humans, consisting of more than 3 billion nucleotides.

1995 - Ian Wilmut and Keith Campbell of the Roslin Institute in Scotland successfully cloned two sheep, Megan and Morag, using cells extracted from differentiated embryos.

Photo courtesy the Roslin Institute

1996 - Ian Wilmut and Keith Campbell cloned the first animal from adult cells. Dolly the sheep, born on July 5, 1996, was created using the so-called Roslin Technique (see "How was Dolly clone?" section of this webpage). The cloning of Dolly is one of the most important milestones in the history of animal cloning, as it proves that cloning of adult animals is possible.

1997 - Two Rhesus Monkeys were cloned by nuclear transfer from the 8-cell stage in the laboratory of Don Wolf at Oregan Regional Primate Research Center.

1997- President Clinton signed a five-year moratorium on the use of federal funds for human cloning.

1997 - Ian Wilmut and Keith Campbell cloned a poll Dorset lamb, Polly, from skin cells grown in a lab and genetically altered to contain a human gene.

Dolly with her three lambs
Dolly with her three lambs
Photo courtesy the Roslin Institute

1998- Dolly gave birth to three healthy lambs, conceived by natural mating.

1998 - Ryuzo Yanagimachi, Toni Perry and Teruhiko Wakayama of the University of Hawaii reported cloning fifty mice from adult cells. They have employed a technique called "The Honolulu Technique" that is more efficient than "The Roslin Technique" used by Wilmut and Campbell to clone Dolly.

2001 - Scientists at Advanced Cell Technology, Inc. announced the birth of a cloned baby bull gaur (a large wild ox) named Noah. Noah was the first endangered animal to be cloned. Although Noah died of an infection unrelated to the cloning procedure, the experiment opened the door to saving endangered species through cloning.

Dolly the sheep 1996-2003
Dolly the Sheep 1996-2003
Photo courtesy the Science Museum

2003 - Dolly the sheep was put down by a lethal anesthetic injection. She suffered from lung cancer caused by a virus. She was six and a half years old. Apart from the cancer and her well-publicized arthritis, she was relatively healthy and normal. (Add picture of "Dolly the sheep 1997-2003")