Mythconception: Did Dolly the sheep have arthritis?

19 December 2017

DOLLY-THE-SHEEP

Dolly the Sheep with her first born lamb, called Bonnie.

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Lewis Thomson has been investigating this tall tail...

Lewis - On the 5th of July 1996, Dolly the sheep was born. She had been created by scientists at the University of Edinburgh. They took the DNA out of a cell from an adult sheep, and inserted it into another sheep’s egg cell which had had the DNA taken out. They then implanted that egg cell into another surrogate mother sheep.

Dolly was the first mammal to have been produced by this cloning process, and quickly became a celebrity. However, at the relatively young age of 6, she had already developed several health problems, including early-onset arthritis and lung cancer. Sadly, she had to be put down.

Concerns were raised about the possible link between cloning and early ageing – and many people became convinced that Dolly’s health problems were caused by her being a clone. If this turned out to be true, it would shatter the hope that cloning could pave the way to producing spare body parts with which we could repair ourselves later...

But now a new study suggests that this is a myth! A paper published last month by Nottingham University’s Sandra Corr and her colleagues has revisited Dolly’s health problems...

Even though Dolly has been dead for almost 15 years, and all of the original reports of her arthritis have long since been lost, her skeleton is preserved in the National Museum of Scotland, in Edinburgh.
So Corr and her team carried out a detailed radiological - X-ray - investigation of the remains of Dolly, as well as her daughter Bonnie (who was born naturally), and of two other cloned sheep, Megan and Morag.
They found that, although there was some arthritis in her elbows and knees, most of Dolly’s joints were fine. In fact, there wasn’t much of a difference between the skeletons of any of the cloned sheep or their offspring, and that of a normal sheep’s skeleton.

Most sheep develop some arthritis in their elbows or knees – as these are the joints which bear the most weight. Pregnancy also increases the risk of arthritis, and Dolly was the mother of six lambs. This suggests that Dolly’s arthritis wasn’t really anything to do with being a clone – but just a natural result of being a sheep, and in particular, a female sheep.

As for the lung cancer, this is also, unfortunately, quite common in sheep. The lung cancer that Dolly had was a specific kind, and is actually caused by a virus called JSRV. Being a virus, it is infectious, and so if one sheep has it, others can get it – and all of those that have it are susceptible to getting lung cancer. Other sheep in Dolly’s flock were diagnosed with the virus, and some of them died because of lung cancer. It’s possible that as Dolly’s flock had to be kept indoors for security reasons, there was an increased risk of the virus spreading, and so, an increased risk of getting lung cancer.

So, it seems that Dolly’s health problems were nothing to do with her being a clone. The original reports of her arthritis were exaggerated, and her lung cancer was caused by a virus – not by early ageing. Having said this, the jury is still out on whether or not there is a link between cloning and early ageing. The DNA of a clone will be older than the DNA of a naturally conceived animal, and this may cause problems in later life. So maybe you should hold off on trying to clone your pet – at least until scientists have looked into this a bit more...

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