Whatever Happened to Dolly, the Cloned Sheep?

If you were old enough to watch the news or read the paper back in the late 1990s, you very likely remember Dolly, the cloned sheep. Born in 1996, the researchers responsible for cloning her kept it quiet for months until their research paper was published.

Dolly’s claim to fame was that she was the very first mammal to be successfully cloned from a single adult sheep cell. Before this, scientists did not know cloning in this manner could result in a living, breathing, healthy animal. The implications were immense, and the world began to both fear and grow excited over what this could mean for human cloning.

How Was Dolly Cloned?

The Roslin Institute in Edinburgh, Scotland, was working on genetically modifying farm animals. They had already done work on introducing new genes into animals, which could then be passed down to the next generation. Their next step was cloning.

Dolly was cloned by taking a single adult sheep cell and placing it inside the empty eggshell of another adult sheep. The egg was then implanted inside of a third sheep, which acted as Dolly’s surrogate mother. Dolly, in effect, had three mothers. But she was a genetic replica of the sheep from which the single cell had been taken.

Scientists were amazed at the outcome because the type of cell Dolly had been cloned from was a mammary cell. It was believed at the time that an adult cell that had already specialized could only be cloned into a duplicate of itself. It was a massive breakthrough to learn that a single mammary cell could create a clone of an entire sheep.

This was not a fast process, though. Dolly was the only successful embryo out of 277 attempts.

Was Dolly Healthy? How Long Did She Live?

Dolly was born like any other sheep. Once her embryo was far enough along, she was implanted in her surrogate mother. She had a normal birth and lived a normal sheep life with her flock at The Roslin Institute. Dolly even had children. She gave birth to six lambs with a Welsh mountain sheep named David.

In 2001, Dolly developed arthritis, which was treated with medication, but did lead to fears that Dolly’s health was suffering. When she was only 6 years old, she developed a progressive lung disease, and the decision was made to have her put to sleep.

While some feared Dolly’s early death meant that cloned animals would suffer from disease leading to early death, The Roslin Institute cloned four other sheep from the same line. These four would go on to lead normal, healthy lives.

Why Did Researchers Clone Dolly?

Researchers didn’t have the end goal of cloning sheep, farm animals, or even family pets, and certainly not humans. The Roslin Institute was interested in genetic engineering. The scientists wanted to use the cloned cells to create therapies and life-saving treatments for humans. They chose sheep because the researchers had experience in breeding sheep. Perhaps being a sheep is part of what caught the public’s attention. A cute and fluffy lamb made a great story for the front page of newspapers around the world.  

It’s More Than Just Genes

Just as twins will have differences, two cloned individuals, while genetically alike, will not be exactly the same. Many factors can affect characteristics, including the environment, food availability, disease, lifestyle, and nutrition.

The four sheep cloned from Dolly’s cell line did not suffer the same bad health as their sister, Dolly. Sheep live an average of 10 to 12 years, and these four — Daisy, Diana, Debbie, and Denise — aged normally, reaching the age of 10.

What Did the World of Animal Science Gain From Dolly?

The research that led to Dolly has inspired countless other scientists to develop new ideas in biology and medicine. Despite fears at the time, Dolly’s cloning has not led to human clones. Cloning animals has not been widespread either. Where the research has really made a difference is with stem cells.

Because Dolly came from an adult sheep’s mammary cell, scientists learned they could change a cell’s gene expression when they swapped its nucleus. Research has advanced to develop cells called induced pluripotent stem cells (iPS). These are artificially created stem cells and can be used for research, limiting the need for embryonic stem cells.

Today, Dolly has been taxidermied and is on display at the National Museum of Scotland in Edinburgh. A popular exhibit, Dolly has been on display there since 2003.