If you ask people today why they use telelphone to communicate with their friends or why they turn to television for entertainment(娱乐),they would look at you as if you were crazy. We don‘t think about a telephone or a television or a car as being strange things. These things have become such an integral(不可缺少的) part of life that they are no longer noticed, let alone(更不用说) remarked upon.
Cloning(克隆，无性繁殖) took a giant leap(飞跃) from science fiction to science fact last year when researchers at the Roslyn Institute in Scotland announced the birth of Dolly, a lamb cloned from the cells of an adult sheep. The achievement raised vast questions about the potential(可能性) of cloning: