The twisting tale of DNA - Judith Hauck

Transcriber: tom carter Reviewer: Bedirhan Cinar

翻译人员: Catherine Gu 校对人员: Binglei Shea

Geckos and grasshoppers, worms and watermelons,

壁虎和蚂蚱、蠕虫和西瓜、

elephants and Escherichia Coli,

大象和大肠杆菌、

man and mushroom. All so different in form and function,

人和蘑菇。所有这些性状都差异巨大，

but amazingly the same in how their form and function are determined.

但令人惊讶的是他们表现的性状却和他们本身的性状一致。

First, all these organisms are made of one or more cells,

首先，所有这些生物体是由一个或多个细胞组成的，

and every cell of every living thing on earth

而且地球上每个生物的每个细胞

contains all the information it takes

都包含着足以

to create and duplicate and make variations of itself.

分裂、复制和分化的所有信息。

That information is stored in a very long but quite simple

这个信息被储存在一个很长但相当简单的

double molecule called DNA,

双分子里，称为DNA，

or Deoxyribonucleic Acid.

或脱氧核糖核酸。

And the DNA of every living organism is made of chains of four smaller molecules

每个生物体的DNA是由四个更小的分子组成的，

called nucleotides. What dictates the difference between a man and a mushroom

称为核苷酸。决定人和蘑菇之间差别的

is the sequence of these nucleotides in the long DNA chain.

是这些核苷酸在DNA长链的序列。

The four differing nucleotide parts, called bases,

四种核苷酸不同的部分被称为碱基，

are made of a few carbon, oxygen, hydrogen, nitrogen and phosphorus atoms,

是由几个碳、氧、氢、氮和磷原子组成的，

and the molecules look like this.

这些分子看上去像这样。

And each of these four bases is attached to an identical backbone molecule,

这四个碱基中的每一个连接到一个相同的主链分子上，

a sugar called deoxyribose - the "D" in DNA - and a phosphate group.

一种称为脱氧核糖的糖 – DNA中的”D” – 和一个磷酸基团。

Let's simplify these nucleotides and show them like this.

让我们来简化这些核苷酸并像这样显示它们。

So, a single sequence of nucleotides joined by their common sugars would look like this.

因此，一个单一的核苷酸序列由它们共同的糖加到一起看上去就会像这样。

And the DNA molecule where such sequences are stored looks like this.

存储这样序列的DNA分子看上去像这样。

But how does a simple molecule dictate the form and function of millions of different living things?

但是，一个简单的分子如何决定 数以百万计的不同生物的性状呢？

You can think of DNA as a great library of information,

你可以把DNA看成是一个巨大的信息库，

information that is used to do one thing and one thing only:

这信息被用只做一件事：

direct the building of different protein molecules.

指导建造不同的蛋白质分子。

And it's the proteins that build the cells and keep them functioning

是蛋白质构建了细胞，并让它工作、

and changing and reproducing. Here's where the familiar word 'gene' comes in.

改变和复制。这就说到了一个熟悉的词’基因’。

If your DNA is a library of information, a gene is a book in that library.

如果你的DNA是一个信息库，基因就是图书馆里的一本书。

A gene is a segment of the DNA molecule.

基因是一个DNA的分子段。

Let's say your body needs a particular protein, like insulin.

比方说，你的身体需要一种特定的蛋白质，如胰岛素。

To get it, some of your cells send a protein signal through the bloodstream

为了得到它，你的一些细胞通过血液给胰腺细胞

to the cells in your pancreas, where insulin is made.

发蛋白质信号，胰腺是分泌胰岛素的地方。

That signal protein tells other proteins in the cell's nuclei

该信号蛋白在细胞的细胞核里告诉其它蛋白质

to open up a part of the DNA double helix, the insulin gene,

打开DNA双螺旋结构的一部分，胰岛素基因，

and start making insulin proteins.

开始制造胰岛素蛋白。

As soon as enough insulin has been produced,

一旦已经产生了足够的胰岛素，

another signal protein comes to the pancreas' cells that tells them to stop making insulin.

另一个信号蛋白质来到胰腺细胞告诉它们停止制造胰岛素。

It's like looking up a book in the DNA library about insulin,

就像在DNA图书馆看一本关于胰岛素的书，

and then putting it back when you're done.

看完了再把它放回去。

There are genes in DNA for visible and invisible things that make up your body,

构成你身体的DNA基因分为显性和隐性两种，

like genes for eye color, protein pigments, for skin color,

例如决定你的眼球颜色、蛋白质色素、皮肤颜色、

for hair color, for stopping and starting bone growth,

头发颜色、骨骼生长开始和结束时间、

for your blood type, for how many fingers or arms and legs you have,

你的血型、长几个手指或几条胳膊和腿、

for proteins that influence how long you live.

和影响你寿命长短的蛋白质的基因。

Your DNA probably contains between 25 thousand and 40 thousand genes,

你的DNA大概包含在2.5万到4.0万个基因之间，

while the DNA of a worm or a plant or a fruit fly

而蠕虫、植物或果蝇的DNA

contains about 12 thousand to 20 thousand genes.

包含大约12000到20000个基因。

Some of those genes have quite different sequences of nucleotides than yours,

其中有些基因和你的基因相的核苷酸序列差别很大，

and some are similar to yours.

而有些又和你的相似。

Though it happens infrequently,

尽管这种情况不是频繁发生，

our own nucleotide sequences can change

但我们自己的核苷酸序列可以改变，

as the result of spontaneous or environmental damage

原因是自发的或环境的破坏，

which might remove or shift a nucleotide position.

这或许会删除或移动核苷酸的位置。

This changes the gene involved, and can then change the protein.

这就改变了有关的基因，可以接着改变蛋白质。

Most of these changes, called mutations,

大部分这样的变化，称为突变，

have very little effect on the organism or its descendants.

对有机体或其后代的影响非常小。

some are mildly damaging,

一些是轻度损害，

and a few can make the organism better-suited to its environment.

一些能使生物体更好地适应它所生存的环境。

It is these tiny changes in DNA gene sequences, happening over millions of years,

正是这些DNA基因序列在数百万年间发生的微小变化，

that create the differences among living organisms, from geckos to grasshoppers.

造成了从壁虎到蚂蚱、

worms to watermelons, elephants to Escherichia Coli, and man to mushroom.

从蠕虫到西瓜、从大象到大肠杆菌以及从人到蘑菇这些生物体之间的差异。