Cloning and DNA
Many people think that the science of genetics and cloning is resent. It’s certainly true that in 1953,Watson and Crick ,two scientists at Cambridge University,England ,discovered the structure of the acid DNA---a transparent twisting ladder made of the fundamental components of life.But in fact,it was in 1866 that Mendel first recorded the results of growing pea plants. He understood that both the parent plants had influenced the genetic make-up of the new plant.
In 1973,biochemists Cohen and Boyer discovered a procedure to use enzymes chemicals formed in the body----to unzip the DNA,to cut out a sequence of genes,and finally to insert them into the host cell and combine with its DNA.
Cloning takes the DNA from a single cell to create a whole new individual. A clone is an organism which is genetically identical to another one.But it’s now certain that no clone is an exact copy because of differences in experiences and upbringing.
There are at least two teams of scientists which are trying to clone humans . Although controversial,there are many valid reasons to do so. An Italian doctor wants to offer cloning as an optional treatment for couples who find it difficult to have have children. But anyone who was a clone of one of their parents would be under unknown psychological pressure throughout their childhood.
Another reason is to reproduce the exceptional human beings. But an Einstein clone might choose a path in life which is contradictory to the one the original Einstein chose.He may even possess new vices instead of existing virtues!

克隆和DNA
很多人以为遗传学和克隆是新兴的科学。确实，直到1953年，Watson和Crick这两位剑桥大学的科学家才发现了DNA的结构--一个X光能穿透的卷曲梯子构成了生命的基本要素。然而，早在1866年Mendel就第一个通过记录豌豆的种植结果证明是亲本影响了子代的遗传特性。

在1973年，生物化学家Cohen和Boyer发现可以使用酶--一种机体合成的化学物质--来使DNA解链并切下一段DNA序列，最后把它插入宿主细胞，使之与宿主的DNA结合。

克隆能单个细胞的DNA创造出一个完整的新个体。克隆个体之间的遗传性征完全相同。但是现在已经确定没有哪个克隆是原来个体的精确复制，这是因为个体经历和培养条件不尽相同。

目前至少有两组科学家正在试图克隆人。尽管存在争议，克隆人类也有不少正当的理由。一位意大利医生准备用克隆手段给那些不能生育的夫妇一个新的选择。但是一个从父母细胞克隆而来的孩子将会经历难以预料的心理压力。

另一个原因是克隆可以用来复制优秀的人。但是一个爱因斯坦的克隆体很可能会选择一条跟原来的爱因斯坦截然不同的人生道路。他甚至会染上新的恶习而不是崇尚美德。