Dolly - The Cloned Sheep

Ian Wilmut of the Roslin institute produced Dolly, the first mammal to have been successfully cloned from an adult cell, as part of research into creating medicines in farm animal's milk. By far, she remains the world's most famous clone as there were cloned animals before Dolly, but they were all cloned from the embryo's DNA and not an adult cell. But, Wilmut admits that the production of Dolly was a lucky accident that occurred when they were trying to make clones from foetal cells and use the adult ones as experimental controls. “We didn’t set out to clone adult cells. We set out to work with—ideally—embryonic stem cells or things like that,” Wilmut says. “Being successful with adult cells was a very considerable, unexpected bonus.” For producing Dolly, the cells were taken from the udder (mammary gland) of a six-year-old Finn Dorset white sheep, and they reprogrammed the growth medium in such a way that the cells remain alive but do not show any growth. They later injected the cell into an unfertilized enucleated egg cell from the Scottish blackface ewe. But before directly implanting it to another Scottish blackface ewe, they cultured the resulting cell for six to seven days to see if it divided and developed normally. Only 29 early embryos were produced from 277 cell fusions, and they were implanted into 13 surrogate ewes. But only one full-term pregnancy was obtained, and after 148 days (standard gestation period of a sheep), the "6LL3" (6.6 kg Finn Dorset lamb 6LLS aka Dolly) was born. Dolly had slightly shorter chromosomes than those of other sheep her age. She was not entirely identical to her genetic mother because she inherited the mitochondria (outside the nucleus) from her egg donor mother. She was mated with a male sheep named David and produced four normal lambs in her short life span, showing that such cloned animals can reproduce. In a nutshell, Dolly's creation was a significant scientific achievement as it demonstrated that the DNA from adult cells, despite having specialized as one particular type of cell, can be used to create an entire organism. But Dolly was indeed produced after 277 attempts, making it clear that it is challenging to clone from an adult cell.

Born on 5 July 1996, Dolly was euthanized at the age of 6 and half years on 14 February 2003. She had arthritis in a hind leg joint, and sheep pulmonary adenomatosis, common among sheep raised indoors. There are questions about her diseases that remain unanswered, like whether or not she caught it from the other sheep housed with her. Her early death has raised more questions about the safety of cloning, both animal and human. The primary debate was about applying the same procedure to subsequent human cloning. Human cloning advocates have lobbied to legalize cloning since Dolly, but so far, this has not happened. Some people cite cloning experiments that have gone askew, like the deformed foetuses with oversized organs, etc., while arguing that cloning is essentially "playing God." Overall, the debate regarding Dolly continues internationally. Nevertheless, Dolly existed, and that in itself is a momentous event in human history.

Fun fact: Dolly was named after the singer and actress Dolly Parton, and the name was suggested by one of the stockmen after he learned that the animal was cloned from a mammary cell.