英语听力文摘 English Digest 207、克隆为什么不是副本

　　Why Clones Aren’t Copies
克隆是英文"clone"或"cloning"的音译，而英文"clone"则起源于希腊文"Klone"，原意是指以幼苗或嫩枝插条，以无性繁殖或营养繁殖的方式培育植物，如扦插和嫁接。在大陆译为“无性繁殖”在台湾与港澳一般意译为复制或转殖或群殖。 中文也有更加确切的词表达克隆，“无性繁殖”、“无性系化”以及“纯系化”。克隆是指生物体通过体细胞进行的无性繁殖，以及由无性繁殖形成的基因型完全相同的后代个体组成的种群。通常是利用生物技术由无性生殖产生与原个体有完全相同基因组织后代的过程。

　　Last time we were talking about how cloned animals, to some people’s surprise, aren’t just copies of their parent animals. In cloned pigs, for example, some come out bristly-haired, some smooth; some are shy, others aggressive.
How can animals share all the same genes² and yet be so different?
Geneticists aren’t sure yet. One possibility is that chemical conditions inside the uterus affect how the fetus³ develops. But there’s also gene¹ expression to consider. Gene expression refers to which genes are turned on and which are turned off.
Every gene in your body comes in duplicate. You get one from your mother and one from your father. Let’s simplify the situation and pretend there’s just one gene that gives you your sparkling personality.
For example, let’s say your mother was a jewel and that your dad was a crank.
In this instance, presuming you’re an angel, we can imagine that the “personality gene” your father gave you is in the “off” position, while the personality gene your mother gave you is in the “on” position. Would your clone have your same personality?
We don’t know, because we don’t know what position that switch will be in. In reality, there are many, many switches, leading to many possible combinations. A clone is a duplication of the genes, but not of the gene expression.
In other words, a clone could share genes and still look and act differently. They aren’t carbon copies–they are separate organisms all to themselves.

1 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

2 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

3 fetus   

n.胎，胎儿

参考例句：

• In the fetus,blood cells are formed in different sites at different ages.胎儿的血细胞在不同时期生成在不同的部位。
• No one knows why a fetus is not automatically rejected by the mother's immune system. 没有人知道为什么母亲的免疫系统不会自动排斥胎儿。