万物简史 第594期:生命的物质(20)

Most of the time our DNA¹ replicates² with dutiful accuracy, but just occasionally — about one time in a million — a letter gets into the wrong place. This is known as a single nucleotide polymorphism, or SNP, familiarly known to biochemists as a "Snip³." Generally these Snips⁴ are buried in stretches of noncoding DNA and have no detectable⁵ consequence for the body. But occasionally they make a difference. They might leave you predisposed to some disease, but equally they might confer some slight advantage — more protective pigmentation, for instance, or increased production of red blood cells for someone living at altitude. Over time, these slight modifications⁶ accumulate in both individuals and in populations, contributing to the distinctiveness⁷ of both.

在大多数情况下，我们的DNA都以极其精确的方式进行复制，但是，在非常偶然的情况下——每100万次大约出现1次，某个字母（碱基）进入了错误的位置。这种情况被称为单一核苷酸多样型（SNP），也就是生化学家所说的Snip。通常情况下，这些Snips被埋没在非编码DNA链中，并不会对身体产生显著的影响。但是偶尔它们也会发生作用，有可能使你容易感染某种疾病，但也同样可能产生某种小小的有利作用——比如更具保护性的肤色，或是增加生活在海拔较高的地区的人的红细胞。这种不太显著的变化不断累积，届时对人与人和人种与人种之间的差异产生了影响。

The balance between accuracy and errors in replication is a fine one. Too many errors and the organism can't function, but too few and it sacrifices adaptability⁸. A similar balance must exist between stability in an organism and innovation. An increase in red blood cells can help a person or group living at high elevations⁹ to move and breathe more easily because more red cells can carry more oxygen. But additional red cells also thicken the blood. Add too many, and "it's like pumping oil," in the words of Temple University anthropologist¹⁰ Charles Weitz. That's hard on the heart. Thus those designed to live at high altitude get increased breathing efficiency, but pay for it with higher-risk hearts.

在DNA的复制过程中，精确性与差异性必须保持平衡。差异性太多，生物将丧失功能，但差异性太少又会降低其适应性。类似的平衡也必须存在于一种生物的稳定性和创新性之中。对于生活在海拔较高的地方的某个人或某群人，增加红细胞可以使他们活动和呼吸顺畅，因为更多的红细胞能够携带更多的氧气。但是增加的红细胞也会增加血液的浓度。用坦普尔大学人类学家查尔斯·威茨的话来说，太多的红细胞使得血液“像石油”。这对心脏来说是一个沉重的负担。因此那些生活在高海拔地区的人在肺活量增加的同时，也增加了心脏患病的可能性。

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 replicates   

复制( replicate的第三人称单数 )； 重复； 再造； 再生

参考例句：

• The bluetongue virus replicates in the insect. 蓝舌病病毒在这种昆虫体内繁殖。
• The chameleon's skin replicates the pattern of its surroundings. 变色龙的皮肤可随环境的模式而改变颜色。

3 snip   

n.便宜货，廉价货，剪，剪断

参考例句：

• He has now begun to snip away at the piece of paper.现在他已经开始剪这张纸。
• The beautifully made briefcase is a snip at £74.25.这个做工精美的公文包售价才74.25英镑，可谓物美价廉。

4 snips   

n.（剪金属板的）铁剪，铁铗；剪下之物( snip的名词复数 )；一点点；零星v.剪( snip的第三人称单数 )

参考例句：

• With a few quick snips of the shears he pruned the bush. 他用大剪刀几下子就把灌木给修剪好了。 来自辞典例句
• Pick up the snips of cloth and thread from the floor. 拾起地板上的布片和线头。 来自辞典例句

5 detectable   

adj.可发觉的；可查明的

参考例句：

• The noise is barely detectable by the human ear.人的耳朵几乎是察觉不到这种噪音的。
• The inflection point at this PH is barely detectable.在此PH值下，拐点不易发现。

6 modifications   

n.缓和( modification的名词复数 )；限制；更改；改变

参考例句：

• The engine was pulled apart for modifications and then reassembled. 发动机被拆开改型，然后再组装起来。 来自《简明英汉词典》
• The original plan had undergone fairly extensive modifications. 原计划已经作了相当大的修改。 来自《简明英汉词典》

7 distinctiveness   

特殊[独特]性

参考例句：

• Q10. How are the newness and distinctiveness of a design assessed? 如何评估一项外观设计的新颖性和独特性？
• We will add your biological and technological distinctiveness to our own. 你们的文化将会适应为我们服务。

8 adaptability   

n.适应性

参考例句：

• It has a wide range of adaptability.它的应用性广。

9 elevations   

（水平或数量）提高( elevation的名词复数 )； 高地； 海拔； 提升

参考例句：

• Weight of the crust changes as elevations are eroded and materials are deposited elsewhere. 当高地受到侵蚀，物质沉积到别的地方时，地壳的重量就改变。
• All deck elevations are on the top of structural beams. 所有甲板标高线均指结构梁顶线。

10 anthropologist   

n.人类学家，人类学者

参考例句：

• The lecturer is an anthropologist.这位讲师是人类学家。
• The anthropologist unearthed the skull of an ancient human at the site.人类学家在这个遗址挖掘出那块古人类的颅骨。