万物简史 第578期:生命的物质(4)

DNA¹ exists for just one reason — to create more DNA — and you have a lot of it inside you: about six feet of it squeezed into almost every cell. Each length of DNA comprises some 3.2 billion letters of coding, enough to provide 103,480,000,000 possible combinations, "guaranteed to be unique against all conceivable odds," in the words of Christian² de Duve. That's a lot of possibility — a one followed by more than three billion zeroes. "It would take more than five thousand average-size books just to print that figure," notes de Duve. Look at yourself in the mirror and reflect upon the fact that you are beholding³ ten thousand trillion cells, and that almost every one of them holds two yards of densely⁴ compacted DNA, and you begin to appreciate just how much of this stuff you carry around with you. If all your DNA were woven into a single fine strand⁵, there would be enough of it to stretch from the Earth to the Moon and back not once or twice but again and again. Altogether, according to one calculation, you may have as much as twenty million kilometers of DNA bundled up inside you.

DNA存在的原因只有一个——生成更多的DNA——你的身体内有很多DNA：将近2米长的DNA挤在差不多每个细胞里。每单位长度的DNA包括32亿个密码字母，足以产生103480000000种组合，用克里斯琴·德迪夫的话说，“无论如何可以确保独一无二的地位”。这个概率很大——1的后面加上30多亿个零，“光是印刷这些数字，就要用5000本一般大小的书。”德迪夫解释说。仔细端详镜子中的你自己，想一想这样一个事实，你含有1亿亿个细胞，几乎每一个细胞又都包含约2米长的挤成一团的DNA，你就会意识到你身上有多少这种东西。如果将你身上所有的DNA连成一条细线，它的长度不是地球到月球距离的一个或两个来回，而是好几个来回。根据一种统计，你身上的DNA总长度达2000万公里。

Your body, in short, loves to make DNA and without it you couldn't live. Yet DNA is not itself alive. No molecule⁶ is, but DNA is, as it were, especially unalive. It is "among the most nonreactive, chemically inert⁷ molecules⁸ in the living world," in the words of the geneticist Richard Lewontin.

一句话，你的身体喜欢制造DNA，没有它你就不能生存。然而DNA本身并没有生命。分子也没有生命，但DNA可以说是尤其没有生命。用遗传学家理查德·莱旺顿的话来说，它是“生命世界中最非电抗性的化学惰性分子”。

1 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

2 Christian   

adj.基督教徒的；n.基督教徒

参考例句：

• They always addressed each other by their Christian name.他们总是以教名互相称呼。
• His mother is a sincere Christian.他母亲是个虔诚的基督教徒。

3 beholding   

v.看，注视( behold的现在分词 )；瞧；看呀；（叙述中用于引出某人意外的出现）哎哟

参考例句：

• Beholding, besides love, the end of love,/Hearing oblivion beyond memory! 我看见了爱，还看到了爱的结局，／听到了记忆外层的哪一片寂寥！ 来自英汉 - 翻译样例 - 文学
• Hence people who began by beholding him ended by perusing him. 所以人们从随便看一看他开始的，都要以仔细捉摸他而终结。 来自辞典例句

4 densely   

ad.密集地；浓厚地

参考例句：

• A grove of trees shadowed the house densely. 树丛把这幢房子遮蔽得很密实。
• We passed through miles of densely wooded country. 我们穿过好几英里茂密的林地。

5 strand   

vt.使（船）搁浅，使（某人）困于（某地）

参考例句：

• She tucked a loose strand of hair behind her ears.她把一缕散发夹到了耳后。
• The climbers had been stranded by a storm.登山者被暴风雨困住了。

6 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

7 inert   

adj.无活动能力的，惰性的；迟钝的

参考例句：

• Inert gas studies are providing valuable information about other planets,too.对惰性气体的研究，也提供了有关其它行星的有价值的资料。
• Elemental nitrogen is a very unreactive and inert material.元素氮是一个十分不活跃的惰性物质。

8 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。