Photo: Science Examiner
Edinburgh, Scotland (BBN) - Dolly was a female domestic sheep, and the first animal cloned from an adult somatic cell, using the process of nuclear transfer.
She was cloned by Keith Campbell, Ian Wilmut and co-workers at the Roslin Institute, part of the University of Edinburgh, Scotland on 5 July 1996, reports Science Examiner.
When the sheep was put down before her seventh birthday in 2003, she was said to experience an age-related osteoarthritis, raising red flags that clones may grow old faster.
But scientists said on Thursday that the fear of premature, clone-related ageing appears to have been misplaced. Dolly’s joint disease was, in fact, quite understandable.
Researchers in Scotland and England based their conclusion on X-rays of Dolly’s skeleton, held by National Museums Scotland, in Edinburgh. Dolly was inadequate on one joint, but the extent of osteoarthritis revealed by the scans was not typical for a seven-to-nine-year old, commonly conceived lamb.
According to the findings were published in the journal Scientific Reports that the first attention that cloning had induced early-onset OA in Dolly were baseless. The scientists concluded, adding that their research was driven by a desire to set the record straight. She was put down at the age of six years and eight months due to a growing lung disease.
Dolly’s breed of Finn-Dorset sheep usually lives for around 10-12 years. The researchers said their verdicts were backed up by X-rays of the skeletons of Bonnie, Dolly’s naturally-conceived daughter, and of Megan and Morag sheep cloned using a separate technique. Their bones are also in the NMS collection.
The only legal record of OA in Dolly was a brief mention in a submission to a scientific conference, said the team. None of these original diagnostic documents was preserved. The same team published a study last year in which they reported that four genetically-identical copies of Dolly had aged with no symptoms of osteoarthritis. Debbie, Denise, Dianna and Daisy the identical sisters of Dolly born 11 years later were made from the identical mammary gland cell line that generated the world’s most famous sheep.
None of them was a lame, and none had osteoarthritis uncommon for their age.
Osteoarthritis is a very severe disease generated by mechanical wear and tear on joints. It can be hereditary in origin, but risk factors include old age, obesity and trauma. At age nine, none of the Dolly’s four sisters was diabetic, and all had normal blood pressure.
The researchers acknowledged there were a few limitations to their research including that only the bones of the sheep were available, whereas OA is the disease of the whole joint, including the ligaments and cartilage. Also, X-ray proof of OA does not necessarily reflect the extent of illness experienced by an animal.
Dolly was generated using the somatic-cell nuclear transfer. It involves removing the DNA containing nucleus from a cell other than an egg or sperm and implanting it into an unfertilized egg from which the core had been removed.
Animal cloning is used in agriculture, mainly to create breeding stock, and in the business of recreating people’s dead pets.
BBN/MMI/ANS