DOLLY SHEEP- SHORT STORY ABOUT CLONING
Dolly the sheep, as the first mammal to be cloned from an adult cell, is by far the world's most famous clone. However, cloning has existed in nature since the dawn of life. A clone has the same DNA sequence as its parent and so they are genetically identical.
Several clones had been produced in the lab before Dolly, including frogs, mice, and cows, which had all been cloned from the DNA from embryos. Dolly was remarkable in being the first mammal to be cloned from an adult cell. This was a major scientific achievement as it demonstrated that the DNA from adult cells, despite having specialised as one particular type of cell, can be used to create an entire organism.
“Dolly (right) the first cloned sheep stands in her pen at Edinburgh's Roslin Institute with Polly another cloned sheep.”
HOW DOLLY WAS CLONED
Animal cloning from an adult cell is much more difficult than from an embryonic cell. So when In 1996 Ian Wilmut and his colleagues at the Roslin- Institute in Edinburgh, Scotland, successfully cloned a sheep.
Wilmut and his colleagues transplanted a nucleus from a mammary gland cell of a Finn Dorsett sheep into the enucleated egg of a Scottish blackface ewe. The nucleus-egg combination was stimulated with electricity to fuse the two and to stimulate cell division. The new cell divided and was placed in the uterus of a blackface ewe to develop. Dolly was born after 148 days on 5th July, 1996. The lamb born from 277 cell fusions but only 29 early embryos developed and were implanted into 13 surrogate mothers. Only one pregnancy went to full term.
WHY DOLLY?
The cell used as the donor for the cloning of Dolly was taken from a mammary gland, and the production of a healthy clone therefore proved that a cell taken from a specific part of the body could recreate a whole individual. On Dolly's name, Wilmut stated "Dolly is derived from a mammary gland cell and we couldn't think of a more impressive pair of glands than Dolly Parton's"
DOLLY HAD A FATHER?
“In the picture we can see Dolly and her surrogate mothers”
DOLLY’S LIFE
In an attempt to allow Dolly to have as normal as life as possible it was decided that she should be allowed to breed. A small welsh mountain ram was selected as her mate and between them they successfully produced six lambs. Their first, Bonny, was born in the spring of 1998. Twins followed the next year and triplets the year after that. Press interest in Dolly had quietened down for a while until, in the autumn of 2001, Dolly was seen to be walking stiffly. X-rays confirmed that Dolly did indeed have arthritis.
This was a blow to everyone and again fuelled the suspicion that cloned animals were destined to age prematurely. The cause of the arthritis was never established but daily anti-inflammatory treatment resolved the clinical signs within a few months.
In January 2000, one of the sheep, Cedric, died. The post mortem revealed that Cedric had died of sheep pulmonary adenomatosis (SPA). This disease is caused by a virus that induces tumours to grow in the lungs of affected animals. The disease is incurable. The animal carers were clearly concerned as to whether Dolly was infected with the same virus. The virus is infectious and spreads from sheep to sheep by close contact.
The animal carers hoped that Dolly might be free of infection. Dolly was immediately placed in isolation; she could see and hear other sheep and was housed with her first lamb Bonny, but was prevented from mixing with all other sheep. Even worse news soon followed when in March, Morag, succumbed to the same disease. She had been housed with Dolly for many years so the chance that Dolly was not infected were slim. When, in September one of Dolly's second litter of lambs was also diagnosed with SPA, it became certain that Dolly herself must be infected. At that point it was decided that her isolation served no purpose and Dolly was returned to the flock of cloned sheep. The most important task was to ensure that, if Dolly did develop the disease, she should not be allowed to suffer. Dolly remained healthy until Monday the 10th February 2003 when an animal care worker reported that he had noted Dolly coughing. Full veterinary examinations and blood tests were conducted. The scan confirmed worst fears, tumours were growing in Dolly's chest. Since a general anaesthetic had been necessary to perform the CT scan it was decided that it would be best if Dolly did not regain consciousness and an overdose of an anaesthetic agent was administered to end her life.
WHAT NOW?
Dolly was given to National Museums Scotland and her remains were conserved by our taxidermists as an exhibit. She is now on display in the Connect Gallery, National Museum of Scotland. Dolly has been enormously popular, with visitors coming from all over the world to see her. She has even travelled to Hungary to open a new science museum in Budapest!