Animal cloning does not lead to long-term health effects

27 July 2016

Posted by: UAR news team

Category: Communications & media

Animal cloning does not lead to long-term health effects states University of Nottingham.

20 years ago, Dolly the sheep, the first ever cloned mammal was born. Yet, six and a half years after her birth, Dolly was put down due to infection. Until now, cloned animals were thought to be born ‘pre-aged’ due to the cells used to clone them. Professor Kevin Sinclair and his team have now published a paper illustrating the healthy ageing of cloned animals. Four ewes – Debbie, Denise, Dianna and Daisy – were cloned from the same mammary gland cells used to make Dolly. A further nine sheep, aged between seven and nine years, were also cloned by the University. Dolly’s sisters, having just celebrated their 9th birthday, plus the other nine sheep, are healthy and do not display any major health implications.

Several of the animals display mild, and in one case moderate (Debbie), signs of osteoarthritis. But, the condition is not severe enough to treat and is common amongst animals of a similar age. Assessments of glucose tolerance, insulin sensitivity, blood pressure and musculoskeletal investigations determined how healthy the sheep were. The results are comparable to "control" sheep aged between five and six years old. No major health issues such as diabetes or abnormal blood pressure are observable. Whilst the tests were conducted last year, Sinclair has confirmed that the animals are remarkably healthy one year on.

Whilst cloning of farm animals and the sale of produce derived from cloned animals has been banned in the EU, this research still has important implications for medical advancement. Growing genetically identical tissue from a patient’s cells using the cloning process would have huge benefits for personalised medicine. Even with the advancement of technologies that allows human skin cells to be reprogrammed, the original cloning research can still play an important role in understanding the efficiency of the reprogramming process.


To clone a sheep, the nucleus of a cell is removed from sheep A and inserted into a nucleus-free egg from sheep B. The egg is fertilised in the lab and the embryo is inserted into sheep C. The resulting offspring is a genetically identical copy of sheep A. This is called somatic-cell nuclear transfer (SCNT).

When the cloned and “control” animals were compared, a difference in telomere length was observed. A telomere is a protective nucleotide sequence at the end of a chromosome and they’re variable length in cloned animals has led to questions about the biological age of cloned cells. However, research in this area has determined that human somatic cells reprogrammed to pluripotency (immature cells) generally displayed elongated telomeres, suggesting that they will not age prematurely.

Further reading

Healthy ageing of cloned sheep

Telomere Dynamics in Human Cells Reprogrammed to Pluripotency