The concept of mammalian clones, even humans, was not completely new. Naturally occurring genetic clones, or individuals genetically identical to one another, had long been recognized in the form of monozygotic (identical) twins (twin). Unlike Dolly, however, such clones are derived, as their scientific name indicates, from a single zygote, or fertilized egg. Moreover, clones had been generated previously in the laboratory, but only from embryonic cells (cell) or from the adult cells of plants (plant) and “lower” animals (animal) such as frogs (frog). Decades of attempts to clone mammals from existing adults had met with repeated failure, which led to the presumption that something special and irreversible must happen to the DNA of mammalian cells during the animal's development. Indeed, until 1997 it had been generally accepted dogma that adult mammalian cells are no longer genetically totipotent, or capable of giving rise to all of the different cell and tissue types (e.g., liver, brain, and bone) required for making a complete and viable animal. It was presumed that somatic-cell differentiation, the process by which a single fertilized egg is converted into all of the different cell types found in an adult, involved some irreversible, likely epigenetic (epigenetics) step. That Dolly remained alive and well long after her birth—that she had a functional heart, liver, brain, and other organs, all derived genetically from the nuclear DNA of an adult mammary-gland (mammary gland) cell—proved otherwise. At the very minimum, the specific tissue from which Dolly's nuclear DNA was derived must have been totipotent. By extension, it was reasonable to suggest that the nuclear DNA of other adult tissues also remains totipotent. With the successful creation of Dolly, this speculation became a testable hypothesis.

On Feb. 14, 2003, Dolly was euthanized by veterinarians after being found to suffer from progressive lung disease. Her body was preserved and displayed at the National Museum of Scotland in Edinburgh.