As the first cloned mammal ever to be created from an adult cell, Dolly the sheep's birth was of huge excitement both to the scientific world and to the public.
Dolly was a part of the Roslin Institute’s research into producing genetically modified farm animals or livestock. Their work was focused on introducing new genes into livestock so they display a new trait which can then be passed on to their offspring. Cloning was the next step in their research.
Dolly was the first mammal to be cloned from an adult cell. Before Dolly was born, this was thought to be impossible. Scientists believed that specialised adult cells, those that had a certain job (like a skin cell or a liver cell), only held the information to do with that job. Dolly was grown from a single mammary cell which contained all the information to create a whole new sheep.
Dolly started her life as a single cell in a test tube taken from the mammary gland of a Finn Dorset sheep and an egg cell from a Scottish Blackface Sheep. Once normal development was confirmed in a lab at six days, the embryo was transferred into a surrogate mother. Dolly was then born on 5 July 1996 and named after the country western singer Dolly Parton.
The birth of Dolly was kept under wraps until the publication of Roslin Institute’s research paper could be prepared. Her birth was announced on 22 February 1997, and the world’s press descended on Roslin to meet the now famous sheep. After her reveal it sparked a debate in the press around the ethics of cloning.
Dolly with her triplets Lucy, Darcy and Cotton. Photo courtesy of the Roslin Institute, University of Edinburgh, UK
Dolly spent her whole life living in a flock of sheep at the Roslin Institute. Dolly had six lambs with a Welsh Mountain sheep named David. Their first lamb, Bonny, was born in the spring of 1998. Twins, Sally and Rosie, followed the next year and triplets, called Lucy, Darcy and Cotton, the year after that.
In the autumn of 2001, Dolly was seen to be walking stiffly. X-rays confirmed that Dolly had arthritis. It 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.
Although her arthritis was a concern for the animal carers at Roslin, a much more serious problem was feared. In January 2000, a cloned sheep called 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 and is incurable.
Dolly remained healthy until Monday 10 February 2003, when an animal care worker reported that he had noted her coughing. Full veterinary examinations and blood tests were conducted but failed to establish a diagnosis. A CT scan was carried out on 14 February 2003. The scan confirmed the team's 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 she was put to sleep at the age of six.
Dolly captured the public imagination and was donated to National Museums Scotland by the Roslin Institute. She has been on display at the National Museum of Scotland since 2003 and is popular with visitors of all ages.
Dolly the sheep has been scanned and digitally reconstructed as a 3D model. Take her for a spin and see her like never before.
Header image: Dolly the sheep on display at the National Museum of Scotland.