背景大鏈接.

Cloning is the asexual production of an exact copy of an original. So for example， one could use cloning to produce the exact copy of a single cell. The cell copy would be identical to the first cell and would have the same exact DNA sequence. In many cases， cloning has been used to reproduce type specific cells. In some instances， cloning of an individual organism， like the sheep， Dolly， has been possible.

Unlike reproduction that involves two “parents，” such as a male and female plants， cloning has a single parent. This is often used in reproducing certain plants. Certain plants have undergone cloning processes for thousands of years， but they do not play a part in the ethical debates that surround cloning of animals， and most particularly humans.

有例可證，動物克隆的嘗試始于20世紀50年代，多莉則克隆成功于1996年。將其父源基因移植到一去核卵子得以實現(xiàn)，這一技術稱作體細胞核移植。改細胞隨之采用多種化學物質進行培育，最終得到了對其父源完全克隆的多莉。

For example， reproductive cloning of animals was first attempted in the 1950s. Most identify the sheep Dolly， cloned in 1996. Dollys parent had DNA transferred into an egg that had its nucleus removed. This is called a somatic cell nuclear transfer. The cell was then treated with chemicals and stimulated to grow so than an almost exact replicate of the cloned sheep was born.

克隆就是通過無性繁殖，對原體的精確復制。舉例來說，細胞就可以被完全復制。生成的細胞與原細胞一模一樣，甚至基因鏈也相同。普通實驗都是克隆特型細胞。當然，克隆羊多莉的成功表明有機體的克隆也是可行的。

有些植物分雌雄，其后代有父有母，而克隆產物不同于此，只有一個父源。有很多植物也是單性繁殖，數(shù)千年如此而不會有倫理問題。但一旦涉及動物甚或人類，倫理問題便凸顯了。