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DNA的真面目 – 译学馆
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DNA的真面目

DNA Doesn’t Look Like What You Think!

[美国公共广播公司]
[PBS Intro]
我很遗憾地告诉你
I hate to tell you this,
如果你曾经看过生物书上的内容 有可能
but if you’ve ever looked at a biology textbook, chances are
它正在欺骗着你
it was lying to you.
或者至少没有告诉你关于DNA的全部故事
Or at least not telling you the whole story–about DNA.
接下来 我们会告诉你全部
Today,we’re going to fix that.
开始
[OPEN]
快问快答 当我说到“DNA”时 你脑海中呈现出怎样的画面
Real quick, what image comes to mind whenI say “DNA”.
你已经想到了吗?
Have you got it?
可能你正在想着这样或是那样的图像
You’re probably imagining something likethis, or this, or maybe this?
但DNA并不是我们想象的那样
That’s not what DNA looks like.
当然你不可能精确地去给DNA拍个照片
Of course you can’t exactly take a photograph of DNA,
或者是通过一般的显微镜去观察它
or see it through your typical microscope.
它非常小
It’s simply too small.
一个DNA双螺旋结构仅仅2纳米宽
A double helix of DNA is just 2 nanometerswide.
一条DNA链与一根头发相比就好像
A DNA strand next to a piece of hair is
一个人站在罗德岛州边上一样
like a person standing next to The State of Rhode Island.
即使最好的光学显微镜也不能
Even the best light microscopes can’t
看到小于200纳米的东西 因为
see anything much smaller than about 200 nm, because, well,
光不能与比它波长更小的东西相互作用
light can’t really interact with somethingsmaller than its wavelength.
这也是科学家要用电子显微镜
This is why scientists look at super-small things
去观察特别小的东西的原因
with electron microscopes
因为电子的波长比可见光的波长要小很多
because the wavelength of an electron can be a LOT smaller than visible light.
但是即使是这样 电子显微镜也不能给我们提供
But even that doesn’t give us
像DNA那样小事物的一个很好的图像
a very good picture of something as small as DNA.
罗莎琳德·富兰克林的著名的影像
Rosalind Franklin’s famous image,
也就是她用波长比可见光小的X射线拍到了
that solved the double helix structure, was made by shooting
DNA分子的双螺旋结构
DNA with X-rays, which are also smaller thanvisible light.
但是它并不是真正的DNA的照片
But it isn’t really a picture of DNA,
它更像是DNA的阴影
it’s more like DNA’s shadow.
我们做的最好的事是用一个非常小的针头穿过DNA
The best we’ve done, is by basically dragginga ridiculously small needle across the DNA
然后感觉碰撞 这有点像纳米级唱片播放器 现在
and feeling the bumps, sort of like a nanometer scale record player. Now,
所有这些还有一些其他的办法给了我们
all these methods and others have
一个准确清晰的DNA双螺旋模型
given us an accurate model of DNA’s double helix.
但是这……这些还不是完整的故事
But still… this isn’t really the whole story,
因为那并不是DNA
because that’s not how DNA looks
在我们细胞里的样子
inside our cells.
我们的每一个细胞拥有两米长的DNA
Each of our cells holds 2 meters of DNA
在细胞核里的只有十万分之一米
inside a nucleus just ten millionths of a meter across…
这是令人难以置信的
which is mind-boggling.
准确的说
To put that in perspective,
如果一个DNA双螺旋结构有铅笔线那样宽
if a double helix were the width of a pencil line, one cell’s
那么一个细胞中的DNA就至少可以覆盖一千公里
DNA would stretch a thousand kilometers,
并且包裹在一个不足五米宽的球里
then wrapped in a ball less than 5 meters wide.
为适应我们的细胞
To fit in our cells,
DNA缠绕在蛋白质小粒上 然后再次缠绕
DNA is wrapped around beads of protein, which are coiled again,
一直缠绕 缠绕……缠绕
and then again, and again… and again,
直到我们身体的46条染色体中两米的DNA
until all 2 meters of DNA in our 46 chromosomes
压缩至都小于十分之一毫米为止
measure less than a tenth of a millimeterend to end.
这……就是效率
That… is efficiency.
这些湿软的小形状在
These squishy little shapes are how
教科书里通常被绘制成染色体……这也是个
textbooks usually draw chromosomes… which is also
问题 因为大多数情况下染色体
a problem, because that’s not what chromosomes look
不是这个样子的
like most of the time.
DNA只有在很短的一段时期
DNA looks like this
看起来才是这样 就是当一个细胞分裂成两个不同的细胞时
during a very short window when a cell is dividing into two different cells.
但是当DNA被压缩的那么紧时
But when DNA is packed that tight,
这个细胞就做不了任何事情 例如制造东西
the cell can’t do anything with it, like make stuff.
这时的细胞就像是一本被紧密合上的书
It’s like a book that’s locked shut.
大多数情况下 我们的染色体是部分松散的
Most of the time, our chromosomes are partly unwound,
呈现一个中等大小的形状
in one of those medium-sized coily shapes.
现在 我不能把我的耳机放进我的口袋里
Now I can’t even put headphones in my pocket
除非打五个结 因此你可能
without tying five knots, so you’re probably
想知道我们的DNA是如何摆脱完完全全的混乱状态的
wondering how our DNA keeps from getting hopelesslytangled.
为了回答这一问题
To answer that,
科学家最终解决了如何三维地观察细胞里的DNA
scientists have finally figured out how to look at a cell’s DNA in three dimensions
这 就是3D状态下的基因组
This is a genome in 3-D.
我们习惯在纸上或是荧幕上看到DNA
We are so used to looking at DNA on paper,
但是我们忽视了它是浮动于
or on a screen, we forget this stuff is floating
三个维度中的
around in three dimensions.
但是细胞核不仅仅是一个装满拉面的包
But the nucleus isn’t just a bag full oframen noodles.
事实证明那里有许多超乎我们想象的组织
Turns out there’s a lot more organizationthan we thought.
细胞核外部覆盖了一层网状纤维构成它的骨架
The nucleus is coated with a mesh of fibers that give it structure,
同时染色体
and chromosomes get
依附到纤维骨架上
anchored to this mesh.
不能让它们乱七八糟的漂浮在细胞核里
Can’t have them just floating around allwilly-nilly.
事实证明在那个网中每条染色体都挂在
Turns out each chromosome hangs out
属于自己的“领地”里
in its own “ territory ” inside that web.
被读取和制造的DNA
The part of the chromosome that’s
的染色体部分位于细胞核中心附近
being read and making stuff is near the center,
而未被读取的DNA通常更接近边缘
while DNA that’s not being read is usually closer to the edge,
真扎心啊
wound up tighter.
你的每一个染色体的两个复制体
The two copies of each
甚至都不相邻
of your chromosomes aren’t even next to each other.
基因的开与关不仅仅依据一串小标记
Genes are turned on and off not just by little flags on a string,
但是DNA是依据什么
but by how that DNA is
在三维空间中组织的
organized in three-dimensional space.
甚至在完全不同染色体上的两段DNA也能在
Even two bits of DNA on totally separate chromosomes can interact
3维网络中相互作用
in this 3-D web.
这些环和扭曲是如何安排的
How these loops and twists are arranged is
是什么让细胞携带数十亿封密码
what lets cells take billions of letters of
并将其转化为生命
code and turn it into life.
这个组织对于如何让细胞正常运作起到至关重要的作用
This organization is important to how cells function normally,
但这也只是一部分
but it’s also a part
像癌症这类疾病是如何产生的 甚至不同细胞在大脑中是如何表现的
how diseases like cancer arise, even how different cells behave inside the brain.
以简化了的方式看待DNA是有用的
Simplified ways of looking at DNA are useful.
它们能帮助我们学习
They help us learn,
也能告诉我们器官是如何进行复杂的工作的……
they help us tell stories about how these complicated machines work…
但是重要的是记住那并非故事的全部
but it’s important to remember that’snot the whole story.
这些类似的事情有点像是如何用火星五号的蓝图
Kind of like how the blueprints
可以告诉你火箭是如何工作的 但是它们
for a Saturn V can tell you how rockets work, but they
不会告诉你火箭是怎样到达月球的
won’t tell you how to get to the moon.
现在我们得到了更好的DNA图像
Now that we’ve got a better picture,
我们能够看问题 但我们不知道去提问
we’re able to see questions we didn’t even know to ask.
保持好奇心
Stay curious.
只要知道今天我告诉你的所有事情都是
just know everything I told you today
关于真核生物的细胞核的
is for eukaryotes, things with nuclei.
细菌之类的小东西把他们的DNA就包装的完全不同了
Bacteria little stuff like that pack their DNA totally differently.
我也有一点小成果
I also have a little complete
我看到每个在里面的DNA加入旋转
everyone in it I see DNA jion around
并且它像是跑错了方向
and he likes run him wrong direction.
如果你让它运转起来 他是个DNA 它的链条将像你的右手手指一样缠绕
If you work it up,he was a DNA,its chain would wrap like your figures on your right hand
如果你曾见过一个反方向的螺旋
If you ever seen a jion backwords like a left hand
那是不正常的DNA
That’s bad DNA.
如果你看到了不正常的DNA 请在推特上告诉我
If you see it,let me know on twitter,
同时打上“不正常的DNA”的标签
and use the hashtag # badDNA

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视频概述

真实的DNA是什么样子的

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视频来源

https://www.youtube.com/watch?v=aT9T9h-2Jp8

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