Cloned Sheep

Dolly

(July 5, 1996 – February 14, 2003), a ewe, was the first mammal to have been successfully cloned from an adult somatic cell. She was cloned at the Roslin Institute in Midlothian, Scotland, and lived there until her death at the age of six. Her birth was announced on July 5th, 1996. The sheep was originally code-named "6LL3". Since the sheep was cloned from a mammary cell, one of the stockmen who helped with her birth suggested the name "Dolly" in honour of Dolly Parton who is well-known for her large breasts.[1]. The technique that was made famous by her birth is somatic cell nuclear transfer, in which the nucleus of a donor cell is placed in a de-nucleated ovum. The donor nucleus is then reprogrammed by the ovum, and ovum develops into an embryo. When Dolly was cloned in 1996 from a cell taken from a six-year-old Finnish Dorset ewe, she became the centre of much controversy that still exists today.

Dolly the sheep was the first mammal to be cloned from the
DNA of an adult. Here she is with her first-born lamb, Bonnie.

Premature aging

In 1999 research was published in the journal Nature suggesting that Dolly may have been susceptible to premature aging, due to shortened telomeres in her cells[4]. It was speculated that these were passed on from her donor sibling, who was six years old when the genetic material was taken from her, so that Dolly may have been genetically six years old at birth. This is because telomere length is reduced after each cell division, which requires DNA replication before mitosis occurs. The polymerase, part of the replication machinery, cannot reach the end of the chromosome being replicated and clips a little of the telomere at the end off every time replication occurs. Possible signs of her condition were reported in January 2002, when Dolly was five years old. She had developed a potentially debilitating form of arthritis at an unusually early age. This supported the theory of premature senescence, although Dr. Dai Grove-White of the Faculty of Veterinary Science at Liverpool University was reported as saying, "Conceivably arthritis could be due to the cloning but equally it could not be. For all we know, she may have damaged her leg jumping over a gate and developed arthritis." Others speculate that Dolly's arthritis resulted from her lifestyle as a scientific curiosity and protected specimen due to a lack of normal outdoor exercise and unnatural stress on her joints. Supporters of this method of cloning counter that the technique used to clone Dolly simply needs to be refined. However, others contend that with very limited understanding of the nascent field of applied genetics, scientists can not and should not attempt to control the action of so many genes at once. Many outside the scientific community have stated that this is vindication for their initial assertions that any form of cloning is ethically wrong and should be banned.

Death

On February 15, 2003 it was announced that Dolly had died from a progressive lung disease. A necropsy confirmed she had Ovine Pulmonary Adenocarcinoma (Jaagsiekte), a fairly common disease of sheep caused by the retrovirus JSRV. Roslin scientists stated that they did not think there was a connection with Dolly being a clone, and that other sheep on the farm had similar ailments. Such lung diseases are especially a danger for sheep kept indoors, as Dolly had to be for security reasons.

On April 9, 2003 her stuffed remains were placed at
Edinburgh's Royal Museum.