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Cloning of Dolly the Sheep: The Breakthrough of Modern Genetics
- Vatsala Jain
- Apr 4
- 3 min read
In 1996, Dolly the Sheep became the world’s first cloned mammal. But how did scientists achieve success in this mind-blowing experiment, and what does this breakthrough mean for the future of human cloning?
Dolly the sheep
Introduction
Dolly the sheep was born in Scotland in July 1996 and lived until February 2003. She looked and behaved just like any other sheep. She ate and even gave birth. But what made her extraordinary was that she was the first mammal cloned from an adult cell, a groundbreaking moment in science.
This research was led by Professor Sir Ian Wilmut at the University of Edinburgh. Before Dolly, scientists had only cloned smaller animals like frogs, and many believed cloning a mammal from an adult cell was impossible. Cells were thought to be locked into their specialized roles, unable to perform other tasks. Dolly’s birth proved otherwise, a single mammary cell, a type of cell found in the mammary glands which helps produce milk in mammals formed the basis for the development of a whole new sheep.
While this achievement was celebrated, it also raised ethical concerns, especially about the possibility of human cloning. Could the same technology be used to clone people? And if so, should it be?
How was Dolly created
Dolly the Sheep was created using a cloning method called Somatic Cell Nuclear Transfer or SCNT. Scientists took mammary cells from six-year-old Finn Dorset sheep who was Dolly’s genetic mother and allowed them to multiply in vitro (in a lab dish). They then took an egg cell from Scottish Blackface sheep and removed its nucleus. This step was crucial because the experiment aimed to produce a sheep entirely from the mammary cell’s DNA. If the egg’s nucleus had been kept, it would have contained DNA from two different animals, which would have defeated the purpose of cloning.
Next, scientists fused the mammary cell with the enucleated egg (nucleus is removed) using an electric pulse. This process transferred the mammary cell’s DNA into the egg, making it genetically identical to the donor sheep. The electric shock also stimulated the egg, tricking it into behaving as if it had been fertilized, which triggered cell division.
As the egg divided, it developed into an embryo—the early stage of an animal before birth. This embryo was then implanted into a surrogate mother, a Scottish Blackface. After five months, the surrogate gave birth to Dolly, the world’s first cloned mammal from an adult cell.
Dolly’s life
Dolly mostly led a normal life. She gave birth to six lambs, including her first, Bonnie, in April 1998. She was only introduced to the world on February 22, 1997, sparking global media attention. The Roslin Institute announced her birth alongside the publication of their scientific paper. Within a week, the institute received 3,000 calls from around the world as it caused frenzy amount the science community
At one year old, DNA analysis revealed that Dolly’s telomeres (protective caps on DNA) were shorter than expected, suggesting she might have been biologically older than her actual age.
Telomeres reduce as an organism ages,It has been found that telomeres of other cloned animals are similar to or even longer than those of normal animals. However, health screenings showed no direct signs of premature aging.In 2001, she was diagnosed with arthritis, but it was managed with anti-inflammatory medication. Later, she was diagnosed with a lung disease (growing tumors in the chest). It appears that her death was unrelated to the fact that she was a clone, her tumor was caused by a virus that infected both cloned and normal sheep. She was put to sleep at age of 6 to avoid any further suffering.
Dolly and the science community
Dolly meets the Media
She proved that life could be created from a fully developed adult cell through her successful cloning. Researchers have been able to advance genetics, regenerative medicine, and stem cell research as a result of this discovery. The aim of the experiment was not to clone an animal as it has been done before, the aim was to clone using a fully developed adult cell which was thought impossible. This experiment was mentioned in prestigious scientific journals such as Nature and Science News.
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