Dolly the sheep
From Freepedia
Dolly (5 July 1996 – 14 February 2003), a ewe, was the first mammal to have been successfully cloned from an adult cell. She was cloned at the Roslin Institute in Scotland and lived there until her death at the age of six. Scientists announced her birth on 22 February 1997.
The name "Dolly" came from a suggestion by the stockmen who helped in the process, in honour of Dolly Parton, because the cloned cell was a mammary cell [1]. The particular technique that was made famous by her birth is somatic cell nuclear transfer, in which the nucleus from one of the donor's non-reproductive cells is placed into a de-nucleated embryonic cell (which is then coaxed into developing into a fetus). When Dolly was cloned in 1996 from a cell taken from a six-year-old ewe, she became the centre of a controversy that still continues today.
On 9 April 2003 her stuffed remains were placed at Edinburgh's Royal Museum, part of the National Museums of Scotland.
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Controversy
In 1999 research was published in the journal Nature suggesting that Dolly may have been susceptible to premature aging [2], due to shortened telomeres in her cells. It was speculated that these may have been passed on from her parent, who was six years old when the genetic material was taken from her, so that Dolly may have been genetically six years old at birth. However, Dr. John Thomas indicated that most cloned animals actually have telomeres of normal length and in serial clones the telomeres are actually getting longer in each successive generation.
Possible signs of this were reported in January 2002, when Dolly was five years old. She had developed a potentially debilitating form of arthritis at an unusually early age. This supported the theory of premature senescence, although Dr Dai Grove-White of the Faculty of Veterinary Science at Liverpool University was reported as saying, "Conceivably arthritis could be due to the cloning but equally it could not be. For all we know, she may have damaged her leg jumping over a gate and developed arthritis."
The arthritis further fueled worry among some that this form of cloning may not be appropriate for mammals, and there is now a consensus both within and outside the scientific community that at this point the risk of unforeseen effects of cloning on the clone makes experiments in human reproductive cloning premature and unethical.
Supporters of this method of cloning counter that the technique used to clone Dolly simply needs to be refined. However, others contend that with very limited understanding of the nascent field of applied genetics, scientists cannot, and should not, attempt to control the action of so many genes at once. Many outside of the scientific community have stated that this is vindication for their initial assertions that any form of cloning is ethically wrong and should be banned.
Death
On February 14, 2003 it was announced that Dolly had a progressive lung disease. A necropsy confirmed she had sheep pulmonary adenomatosis, a fairly common disease of sheep. Roslin scientists stated that they did not think there was a connection with Dolly being a clone, and that other sheep on the farm had similar ailments.
Legacy
After the cloning was successfully demonstrated by Dolly's creators, many other large mammals have been cloned, including horses and bulls. Cloning has left the realm of science fiction and has become a realistic technology, with its risks and promises of great medical progress. Cloning has already become an option for preserving animals that may become extinct and bringing back to life replicas of pets, such as cats and dogs. Work is slowly progressing on the project to recreate the mammoth and other prehistoric animals. In regards to humans, despite the continued opposition, cloning may become a valid reproductive strategy in addition to in vitro fertilisation, surrogacy, adoption and traditional reproduction. It has also paved the way to make the controversial practice of genetic engineering of children more acceptable, first by genetic screening to decrease the risks of a hereditary disease, second to ensure genetic compatibility for stem cell transplantation to siblings [3] and potentially to improving the genetic code of the children to prolong their life expectancy, strengthen the immune system, and increase their intelligence.
External links
- Dolly the Sheep, 1996-2003 from the Science Museum, London
- Roslin Institute: Update on Dolly and nuclear transfer
- Photos of Dolly and other cloned animals at Roslin
