Dolly the sheep, the first cloned mammal, celebrates 26 years

This July 5 marks the 26th anniversary of the birth of the dolly sheep, first mammal cloned from an adult cell. His birth, in 1996, was not announced until seven months later.

Its creators were the scientists at the Roslin Institute in Edinburgh (Scotland), Ian Wilmut and Keith Campbell. Dolly was actually a sheep resulting from a nuclear combination from a differentiated donor cell to an unfertilized, anucleated (no nucleus) egg.

The cell it came from Dolly it was an already differentiated or specialized one, coming from a specific tissue, the mammary gland, of an adult animal (a six-year-old Finn Dorset sheep), which was a novelty.

Until then, it was believed that clones could only be obtained from an embryonic cell, that is, unspecialized. Five months later –on July 5, 1996– Dolly was born, who was the only lamb resulting from 277 fusions of enucleated ovules with nuclei of mammary cells.

Dolly always lived at the Roslin Institute. There she was bred to a Welsh Mountain male to produce six offspring in all. In the fall of 2001, at the age of five, Dolly develops arthritis and begins to walk painfully, successfully treated with anti-inflammatory pills.

On February 14, 2003, Dolly was euthanized due to progressive lung disease. Her species has a life expectancy of about 11 to 12 years. However, Dolly lived only six and a half years. The necropsy showed that she had a form of lung cancer called Jaagsiekte, which is a disease of sheep caused by the JSRV retrovirus.

The Roslin technicians could not certify that there is a connection between this premature death and being a clone, since other sheep from the same flock suffered and died from the same disease. Such lung diseases are a particular hazard in indoor housing, as was Dolly’s for safety reasons.

However, some have speculated that she was a paraplegic, due to her crooked hooves. There was an aggravating factor to Dolly’s death and that was that she had a genetic age of six, the same age as the sheep from which she was cloned. One basis for this idea was the finding of her short telomeres, which are usually the result of the aging process. However, the Roslin Institute has established that intensive check-ups of her health revealed no abnormalities in Dolly that might suggest premature aging.

The stuffed remains of Dolly the sheep are on display at the Royal Museum of Scotland, reports Wikipedia.