The cloning of Dolly the sheep

It was on July 5th, 1996, that Dolly came into this world. Dolly was unusual, in that she did not have a mixture of her father’s and mother’s genes, but instead had only an exact copy of her mother’s. Dolly was not an example of virgin birth, but of cloning, and she was a sheep, probably the most famous one in the world.

She was produced by a partnership of the Roslin Institute of the University of Edinburgh and the biotechnology company PPL Therapeutics. She was the product of somatic cell nuclear transfer, in which a cell nucleus, in this case from a mammary gland, was inserted into a developing egg cell whose own nucleus had been removed. Electric shock stimulated it to divide, and the resulting blastocyst was gestated in a surrogate mother.

Her name was a tribute to Dolly Parton, because her creators couldn’t think of any more impressive mammary glands. Dolly the sheep died aged six-and-a-half, instead of the more normal 11 or 12 years, but it was of a progressive lung disease (Jaagsiekte), common among sheep, caused by a retrovirus and unrelated to her cloned origins. Indeed, in 2016, four identical clones of Dolly were still alive and well aged 9 years, and Dolly herself produced 6 healthy lambs. The scientists found no defects in other cloned sheep.

Since Dolly, many other animals have been cloned, including pigs, deer, horses and bulls. Chines biotechnicians report a 70-80% success rate for cloned pigs, and the Korean company Sooam Biotech produces 500 cloned embryos a day. The first cloned primates were produced in China from a macaque money in 2017, and in 2019, five identical gene-edited cloned monkeys were produced to aid the study of diseases.

Intriguingly, an extinct Pyrenean Ibex was cloned in Spain in 2009, but unfortunately died shortly after birth from lung defects. It did pave the way, however, for the possible revival of extinct species using similar cloning techniques. Researchers are already engaged on projects to restore the dodo, great auk and woolly mammoth, and no doubt others will follow.

There are some who rail against this type of research, arguing that men should not play gods. People argued similarly when Louise Brown, the world’s first “test tube baby” was born by IVF in 1978. Since then more than 8 million children have entered the world through this technique. Gene editing of cloned embryos will enable us to bring up animals resistant to diseases and deformities, though there will be painstaking refinement of techniques along the way to achieving this.

There can be little doubt that humans will be cloned, although the advantages are less obvious, in that it is the shuffling of genes through sexual reproduction that is the engine of the variety that can be tested against the environment. Just as there are companies that can clone a beloved but departed pet, there may well be ones that offer to clone a child that died tragically young. How closely the new offspring will resemble the one lost, however, will depend on how its environmental upbringing will switch on its genetic potential.

Should this be stopped? No, it is what we do. To those who ask what good will come of it, the reply is attributed to Benjamin Franklin who watched the first human balloon flight in Paris, and later to Michael Faraday when asked about electromagnetism. “What good is it?” The reply was, “What good is a new-born baby?” We don’t know, but it has potential.