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The world's first cloned horse was created by fusing the nucleus of a skin cell taken from her surrogate mother with an empty equine egg cell. Tests confirmed that she was the genetic identical twin of her surrogate mother. The reproductive cloning technology was carried out by scientists from the Laboratory of Reproductive Technology in Cremona.
Prometea twice made history when she was born.
1) The world's first cloned horse
2) The first cloned animal to be born by a surrogate mother which also happened to be a genetic twin.
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The Problems with Reproductive Cloning
There are many technical hurdles to overcome in producing a viable cloned embryo. This is one of the many objections that critics of reproductive cloning have.
To create Prometea 841 males and female embryos were constructed. But of those, only eight male and 14 female embryos developed to the blastocyst (a very early stage) of embryonic development. 17 embryos were implanted into mares, which resulted in four pregnancies. Prometea was the only one to survive.
Her name was chosen in part as an answer to critics of reproductive cloning. In Greek mythology Prometheus stole fire from the gods and it's the scientists hope that Prometea presents a brave face people who do not like the technology.
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Prometea, by all accounts, came into the world as a healthy animal, and unlike Dolly the sheep (the world's first cloned animal) has maintained her good health. So much so that she gave birth to a son, called Pegaso, in March 2008. It confirms that cloned animals can live a healthy life and reproduce.
That she can was seen by the scientific team in Italy as a demonstration of the benefits of reproductive cloning in horses. Namely that when sporting horses are young they are castrated, and if they grow up to be champions their genes are lost to the next generation. But if clones can be created, a champion's genes can live on. Rather than thinking of cloning as some science fiction evil, the scientists consider the reproductive cloning of horses to be an assisted reproduction technique.
Despite controversies and limitations of technology, there have been many other cloned animals and the technology continues to improve.