On 5 July 1996, a sheep was born who would go on to inspire entire industries, provide scientists with a new way of helping endangered species, and change medical science in ways that were barely conceivable at the time.
But this was no ordinary sheep. Her very entry into the world was groundbreaking – she was cloned using cells taken from another sheep’s mammary gland as part of an experiment conducted by the Roslin Institute in Midlothian, Scotland. They named her Dolly after the singer Dolly Parton.
At that point, scientists had been dabbling with cloning – the process of creating a genetically identical copy of another living being – since the 1950s, when British biologist John Gurdon found a way to clone African clawed frogs. Despite many attempts, repeating the feat in larger mammals had proven an elusive and near-impossible task.
But like many scientific breakthroughs, the experiment that produced Dolly was something of a fluke. The Roslin Institute scientists had been attempting to clone a sheep using a complex process called nuclear transfer. Using electricity, they transferred the mammary gland cell’s nucleus into an egg cell from a second sheep.
This egg cell now contained all of the DNA from Dolly’s mother, and it grew and developed into an embryo in the lab. “The cloning of Dolly the sheep showed the world that it was possible to essentially reprogramme all the DNA in the nucleus of an adult cell, so it started behaving like an embryonic cell again, giving rise to a new animal,” says Robin Lovell-Badge, who heads the Stem Cell Biology and Developmental Genetics Laboratory at the Francis Crick Institute in London.
The cloning of pets is controversial, but growing in popularity despite its continuing high cost. Viagen says it is now cloning “more and more pets every year”, and has cloned “hundreds” since it first opened for business in 2015.
The firm charges $50,000 (£38,000) to clone a dog, $30,000 for a cat, and $85,000 for a horse. That cost is obviously out of the range of most of us, but a number of famous people have revealed in recent years that they have had their dogs cloned, or were planning to do so.
Back in 2018, Barbra Streisand disclosed that she had used Viagen to clone two puppies from her former pet Samantha. That same year, The Sun newspaper reported that music mogul and talent show judge Simon Cowell was “100 percent cloning” his three Yorkshire terriers.
There are a number of specific cloning techniques, but typically a cell nucleus from the animal you wish to clone is injected into a donor egg that has had its genetic material removed. The egg is then prompted to grow, in a laboratory, into an embryo. The embryo is subsequently implanted in the uterus, or womb, of a surrogate mother who goes on to give birth to puppy, kitten, or foal.
Blake Russell, Viagen’s president, says the genetic material of the animal you wish to clone can be stored almost indefinitely before the cloning process takes place. This is thanks to the use of very low frozen temperatures, or cryopreservation.
“A cloned pet is, simply put, an identical genetic twin, separated by years, decades, perhaps centuries,” he adds. His company says it “is committed to the health and wellbeing of each and every dog and cat with whom we work”, and it adheres to all US regulation.
