万物简史 第577期:生命的物质(3)（在线收听）

The tiny differences in that remaining 0.1 percent — "roughly one nucleotide base in every thousand," to quote the British geneticist and recent Nobel laureate John Sulston — are what endow us with our individuality. Much has been made in recent years of the unraveling of the human genome. In fact, there is no such thing as "the" human genome. Every human genome is different. Otherwise we would all be identical. It is the endless recombinations of our genomes — each nearly identical, but not quite — that make us what we are, both as individuals and as a species.

这千分之一的小小基因差异——用英国遗传学家，最近获得诺贝尔奖的约翰·萨尔斯顿的话说，“每1000个核苷酸基中的约1个”就是赋予我们个性的基础。近年来很重视人类基因组结构的研究。其实根本没有单一的人类基因组这种东西。每一个人的基因组都不相同，否则我们就会完全一样。正是我们基因组的不断重组——每个基因组大体上相同，而又不完全相同，使得我们成为现在这个样，既是许多个体，又是一个物种。

But what exactly is this thing we call the genome? And what, come to that, are genes? Well, start with a cell again. Inside the cell is a nucleus, and inside each nucleus are the chromosomes — forty-six little bundles of complexity, of which twenty-three come from your mother and twenty-three from your father. With a very few exceptions, every cell in your body — 99.999 percent of them, say — carries the same complement of chromosomes. (The exceptions are red blood cells, some immune system cells, and egg and sperm cells, which for various organizational reasons don't carry the full genetic package.) Chromosomes constitute the complete set of instructions necessary to make and maintain you and are made of long strands of the little wonder chemical called deoxyribonucleic acid or DNA — "the most extraordinary molecule on Earth," as it has been called.

但是究竟什么是基因组？什么又是基因？嗯，让我们再从细胞开始吧。细胞内部是一个细胞核，细胞核内就是染色体——共有46束复杂的物质，其中23束来自你的母亲，23束来自你的父亲。你体内的每一个细胞——它们中的99.9999%——携带同样数量的染色体，只有极少数例外。（这些例外是红细胞、一些免疫系统细胞、卵子和精子细胞；由于不同的组织系统原因，它们不携带完整的基因孢。）染色体包含着一组完整的生成和维持你生命所必需的指令，它们由一长串一长串小而神奇的化学物质——脱氧核糖核酸（俗称DNA）组成。DNA被称为“地球上最非同寻常的分子”。