Temporal RNA sequencing was a method of cloning whereby the clone's aging process could be artificially accelerated so as to allow the clone to quickly reach a certain age. Temporal RNA sequencing was a built-in attribute of the clone in question, and needed to be activated before a certain point, or the clone would begin to experience a breakdown of the cellular structure, eventually resulting in death. When this breakdown occurred, the only thing capable of saving the clone's life was a complete blood transfusion from the lifeform who had provided the clone's original genetic material.
Such a condition occurred to Shinzon, a clone of Starfleet Captain Jean-Luc Picard, who was designed to skip nearly thirty years of his life so that he could eventually replace Picard. However, when the plan to replace Picard was deemed too risky, it was abandoned and Shinzon was exiled to the dilithium mines on Remus.
In 2379, Shinzon, at that point a young man, began to manifest the symptoms of the cellular breakdown, symptoms which were only eased by the telepathic stabilization of his viceroy. Shinzon instituted a plan to kidnap Picard and perform the transfusion, but failed in his attempt, ultimately dying in hand-to-hand combat with his progenitor. (Star Trek Nemesis)