To clone a dog, Hwang’s team takes a small sample of tissue from the dog, while it is still living, or within five days of its death – and freezes the cells. Another dog – the breed is immaterial – is selected to supply an egg. In a process called enucleation, the team replace the DNA in the egg with that from the stored sample. This cloned embryo is then transferred into a separate surrogate dog, which will give birth to the puppy and suckle it for around a month.
“Surrogate mothers don’t have to be the same breed,” explains Hwang. “A great dane could, in theory, be the surrogate for a chihuahua puppy. But we tend to use similar-sized breeds. Normally, only one puppy is born, but sometimes we get a litter of three to four puppies. Usually, the client will take all the puppies if this occurs.”
But cloning is far from an exact science, as Hwang admits: “Things can go wrong. In 2005, when Snuppy, our first cloned dog, was born, we had a 2% pregnancy rate. Now it is about 30%. Some traits go wrong. Dogs can be born unhealthy. For example, they can be born with thickened necks or tongues, and experience breathing difficulties. But we guarantee a healthy puppy for our clients, so we will try again. Often the client will take both puppies in this situation. We never put a dog down.”