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Cloning and DNA Many people think that the science of genetics and cloning is recent. It’s certainly true that in 1953, Watson and Crick, two scientist 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 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 talents of 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! A further reason is to obtain a supply of stem cells. Stem cells in embryos are very flexible and can develop into every other type of cell in the body. For example, it could help someone recover from a disease, repair human tissue, or help them walk again after an accident. These stem cells would need to come from an embryo taken from the clone of someone. But the embryo would then be wasted, which many people find unacceptable. What is clear is that some voluntary code of practice among scientists has to be agreed. If not, compulsory government regulations will have to control cloning. A fourth reason for cloning is that some scientists and farmers think it would be handy to clone, for example, a prize cow which can resist bacteria or disease, or to sow a cloned crop which can resist rot or pests. But to rely on a few cloned animals or crops would restrict the biodiversity of the bread. Finally, the latest research into DNA has helped solve crimes by analyzing the suspect’s saliva which they spit at a crime scene or the dirt under their fingernails. 克隆和DNA 许多人认为基因学和克隆技术是最近发现的。确实,1953年,英国剑桥大学的两位科学家沃森和克里克发现了酸性DNA的结构———由生命的基本成分构成的透明弯曲梯状。但事实上,孟德尔在1866年第一个记录了种植豌豆的结果。他了解到植物的双亲都会影响新植物的基因构成。 1973年,生物化学家科恩和博耶发现了如下程序:利用人体内形成的化学物质酶解螺旋DNA,截取一定顺序的基因片断,最后把它们植入宿主细胞,并使之与其DNA结合。克隆技术是从一个单细胞中提取DNA来创造一个全新的个体。一个克隆物是基因与另一个生物个体完全相同的生物体。但是现在确定的是由于在成长经历和抚育方面的差异,任何克隆体都不是一个完全的复制品。 至少有两组科学家正在试图克隆人类。虽然这样做是有争议的,但还是有许多正当的理由。一位意大利医生想用克隆技术为那些很难生育孩子的夫妇提供一种可选择的方法。但是来自父母中的任何一个的克隆人都会在他们的整个童年生活中处于一种未知的心理压力中。 另一个理由是要再造杰出的天才人物。但克隆出来的爱因斯坦也许会选择一条与“原版暠爱因斯坦截然相反的生活道路。他甚至可能会有新的缺点而不是已有的优点。 更深层的理由是获得大量的干细胞。胚胎中的干细胞是很容易适应的并且能发育成身体中的其他种类的细胞。例如,它能帮助人们从疾病中恢复健康,修复人体组织,或帮助人们在事故后重新站起来。这些干细胞要从被克隆物的胚胎中提取。但是胚胎接着也会被浪费掉,许多人都觉得难以接受。很明显,科学家们的一些非官方的行医法规必须被获准。否则,强制性的政府条例必须控制克隆行为。进行克隆的第四个原因是,有些科学家和农民认为克隆很方便实惠,例如:克隆能抵御细菌或疾病的优选奶牛,种植能够抵抗枯病或虫害的克隆作物。但是仅仅依靠少数几种克隆动植物会限制生物种类的多样性。 最后,在DNA的最新研究中,通过分析嫌疑犯在犯罪现场吐的唾液或手指甲下的污垢已帮助解决了许多犯罪行为。 |
