Animal cloning: 25 years since Dolly the Sheep

On 5 July 1996, Dolly the Sheep became the world’s first mammal to be cloned successfully from an adult cell – something that no one thought was possible as it had only previously been achieved through embryo cloning. But, how did scientists achieve this and how has it changed the world we know today?

What is cloning?

When something is cloned, a genetically identical copy is created. This can happen naturally (identical twins), when a cell replicates itself without any outside intervention, or with the help of scientists, where any type of biological material, such as an individual cell or piece of DNA, is duplicated for research purposes. However, when an identical copy is made naturally, they are a clone of the same fertilised egg, as opposed to being a clone of another individual.

How was Dolly created?

Scientists from Scotland’s Roslin Institute, brought Dolly (not pictured here) into the world using cells from the udder of a six-year-old ewe. Using microscopic needles, the sample was cultured in a laboratory, similar to how the first human fertility treatments were carried out in the 1970s. Once they were able to produce healthy eggs, they were implanted into surrogate ewes and, 148 days later, Dolly was born. Her arrival had proven that specific cells could be used to produce an exact copy of the animal that they were originally collected from.

How did people react to the news?

When the birth of Dolly was announced to the public in February 1997, it was met with mixed reactions. Supporters argued that this successful cloning could be the beginning of vital advances in medicine, such as growing organs or cloning embryos to generate the needed stem cells to help treat various diseases and conditions. Some scientists even contemplated the possibility of using this breakthrough as a way to preserve endangered wildlife.

However, critics slammed the news saying that this procedure was unsafe and unethical, fearing that this would be the stepping stones for the next logical move… cloning humans!

What happened to Dolly?

Dolly (not pictured) is said to have led a normal farm-style life with other sheep at the institute, giving birth to six lambs. Sadly, she had to be put to sleep in 2003, at the age of six, because of a virus that led to a progressive lung condition and the development of tumours (other sheep at the institute had also tested positive for the virus). The previous year, Dolly had also been diagnosed with arthritis in her back legs. These issues raised many questions surrounding the potential abnormalities caused by the cloning process despite the fact that links could not be scientifically proven.

The future of cloning

Dolly’s creation was part of a series of experiments that was aiming to develop a better way of producing genetically modified livestock. Scientists were also looking to learn more about cell development and whether cells taken from specific parts of the body, such as the brain or skin, could be used to create an entirely new animal.

Thanks to Dolly, scientists have been able to use this process to duplicate vital stem cells that can be used treat various medical conditions such as spinal injuries and age-related blindness. Before this, doctors would have to rely on the donation of these cells from other humans. More than 20 species have also successfully been cloned since Dolly’s birth, with the meat and milk from cloned animals regularly being farmed and sold with the US, Argentina and Brazil. Some people have also used this technique to clone prized pet dogs and horses!

But, where will it end? Is the birth of scientifically cloned humans closer than we think?

The Roslin Institute / Britannica – Dolly the Sheep / Britannica – Cloning / History / The Ecologist

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