Her name was Dolly, and although she looked like an ordinary sheep, she became one of the most famous animals ever.
That’s because when Dolly was born on July 5, 1996, near Edinburgh, Scotland, she was the first mammal to be cloned from an adult animal.
A clone is a living thing derived from another living thing. As a result, the two have identical sets of genes. Clones are common in nature.
For example, identical twins are clones because they have the same genes. Some forests originate from the sprouting roots of just one tree, so the trees are clones, too.
But Dolly was special. She was the result of cloning done deliberately by people.
Also, scientists used cells from an adult animal to create her — Dolly was much younger than the sheep from which she was cloned, while identical twins are the same age.
Dolly wasn’t the first animal to be cloned — that was a tadpole, back in 1952. And the tadpole had been cloned not from an adult cell but from an embryonic cell, or a cell in its earliest stages.
Some scientists believe that when a cloned animal is born, its body is actually the same genetic age as the animal it was cloned from.
They think cloned animals, therefore, have shortened lifespans, but other scientists disagree. Dolly, the sheep died when she was just 6 years old, while other sheep of her breed tend to live to be 11 or 12 years old.
Since Dolly was cloned, scientists have cloned a number of animals, including a cat, dog, horse and even an endangered animal, the gaur.
In 2009, a Pyrenean ibex became the first extinct animal to be cloned. It was cloned from a frozen skin sample of an ibex but died just minutes after it was born.
Many cloned animals are unhealthy and die of infections. And no one knows how cloning affects an animal’s intelligence or personality.
Because there is so much to learn about cloning, most scientists do not think humans should be cloned. What do you think about cloning humans?