Dolly
In Scotland’s rugged terrain, sheep have been grazing for centuries. Shepherds raise a variety of breeds there, including Scottish Blackfaces and Finn Devons. The lambs conceived throughout the fall are born each spring. Their rapid growth allows them to be found in butcher shops or herds.
Early in 1977, a lamb unlike any other came into the world. This lamb, named Dolly, did not have a father, but she did have three mothers: furthermore, her genes were identical to those of one of her mothers. In a word, Dolly was a clone. Researchers at the Roslin Institute, which is located close to Edinburgh, Scotland, created Dolly by combining a cell from a Finn Dorset ewe’s udder (the genetic mother) with an egg from a Blackface sheep (the egg cell mother). Before the egg was fused with the udder cell, the genetic material in the Blackface ewe’s egg was extracted. It then stimulated the freshly equipped egg to divide. An embryo it generated was placed in the uterus of a different Blackface ewe, known as the gestational or surrogate mother. Dolly was born as a result of the growth and development of this embryo and the surrogate mother’s pregnancy.
After a century of fundamental studies on the cellular foundation of reproduction, the technology that created Dolly was developed. According to normal circumstances, a male sperm cell fertilizes a female egg cell, and the resulting zygote divides to create a genetic entity. In order to create specialized reproductive cells—either eggs or sperm—a specific group of cells within that organism starts a different type of cell division. To create a new baby, an egg from one of these organisms combines with sperm from another. As the child grows up, the cycle repeats itself, generation after generation. Among the sheep that graze on the grasslands in Scotland, however, Dolly did not conform to this standard pattern of reproduction. Clearly, her creators had something else in mind.