克隆小鼠和猪比较容易,而克隆大鼠较难,克隆人类更难,但不会比克隆猴子还困难。没有人知道为什么有些物种的克隆较另一些物种更困难。但对小鼠的研究正帮助人类认识其中的差别,最终将使研究者在利用人类胚胎干细胞治疗疾病和器官移植方面取得更大的成就。就”治疗性克隆”(也被 Cloning mice and pigs is easier, whereas cloning rats is more difficult, cloning humans harder, but not more difficult than cloning monkeys. No one knows why cloning of some species is more difficult than others. However, research on mice is helping people understand the differences and will eventually make researchers more successful in using human embryonic stem cells to treat diseases and organ transplants. As for “therapeutic cloning” (also