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Every human being starts out the same way:
每個人生命都有相同的開始:
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two cells,
分別來自父親和母親
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one from each parent,
的兩個細胞
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found each other and became one.
相遇並合而為一。
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And that one cell reproduced itself,
接著這個細胞複製自己,
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dividing,
分裂、
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and dividing,
分裂、
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and dividing
再分裂
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until there were 10 trillion of them.
直到達到十兆個細胞。
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Do you realize there are more cells in one persons body
你知道人身體細胞的數目
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than there are stars in the Milky Way?
比銀河裡的星星還多嗎?
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But those 10 trillion cells are not just sitting there in a big pile.
但這十兆個細胞不只是隨便堆成一堆。
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That would make for a pretty boring human being!
這樣的人類應該看起來很無趣吧!
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So what is it that says a nose is a nose,
那什麼決定鼻子要成為鼻子、
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and toes is toes?
腳趾成為腳趾呢?
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What is it that says this is bone,
什麼決定這個成為骨頭、
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and this is brain,
那個成為大腦、
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and this is heart,
那個成為心臟、
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and this is that little thing in the back of your throat
和那個在你喉嚨深處的東西—─
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that you can never remember the name of?
那個你一直記不起名稱的東西?
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Everything that you are or ever will be made of
任何組成你的部份
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starts as a tiny link of instructions
都來自一份小小的、
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found in each and every cell.
可在任何細胞中找到的說明書。
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Every time your body wants to make something,
每次你的身體想要建造什麼東西時,
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it goes back to the instruction book,
都會回去看這本說明書
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looks it up, and puts it together.
再進行建造。
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So how does one cell hold all that information?
那細胞是如何保存這些資訊呢?
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Let's get small.
讓它壓縮變小。
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I mean, really small,
我是說,非常小、
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smaller than the tip of a sewing needle.
比針尖還小。
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Then we can take a journey inside a single cell
如果我們能走進細胞
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to find out what makes up the book of you,
去探究這本書的組成,
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your genome.
我們會發現:你的基因體。
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The first thing we see is that the whole genome,
首先我們要瞭解基因體,
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all your DNA,
也就是你所有的DNA,
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is contained inside its own tiny compartment
是被存放在一個叫做細胞核
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called the nucleus.
的小地方。
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If we stretched out all the DNA in this one cell
如果我們把一個細胞的 DNA 拉直
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into a single thread,
成一條線,
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it would be over 3 feet long!
這條線會超過 3 英尺(約 91 公分)!
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We have to make it fit in a tiny compartment
我們比須把它局限在一個
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that is a million times smaller.
僅百萬分之一倍的小空間。
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We could just bunch it up like Christmas lights,
我們可以把它亂捲一通,像聖誔燈一般,
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but that can get messy.
但這樣就太凌亂了。
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We need some organization.
我們需要一些整理方法。
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First, the long thread of DNA wraps around proteins
首先,線狀的 DNA 會纏繞一些蛋白質
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clustered into little beads called nucleosomes,
變成稱為核小體的小珠子,
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which end up looking like a long, beaded necklace.
它會看起來像是一條長長的串珠項鏈。
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And that necklace is wrapped up in its own spiral
接著,這條項鏈會繞成
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like an old telephone cord.
像是電話線一樣的螺旋。
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And those spirals get layered on top of one another
再來,這些螺旋會相互交疊
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until we get a neat little shape that fits inside the nucleus.
直到可以整齊地放進細胞核中。
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Waaah! Three feet of DNA squeezed into a tiny compartment.
哇!3 英尺的DNA就這樣擠進小小的空間。
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If only we could hire DNA to pack our suitcases!
真希望我們可以用相同的機制打包行李!
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Each tiny mass of DNA is called a chromosome.
每一小團 DNA 被成為染色體。
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The book of you would have 46 chapters,
在這本說明書中有 46 章
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one for each chromosome.
每一章就是一條染色體。
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23 chapters of your book came from your mom,
說明書的其中 23 章來自你的母親,
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and 23 chapters came from your dad.
另外則來自你的父親。
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Two of those chapters, called "X" and "Y",
其中被稱為 X 和 Y 的兩章,
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determine if you are male, "XY",
會決定你是男生,也就是 XY;
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or female, "XX".
或是女生,也就是 XX。
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Put them together and we get two almost identical
它們會組成兩套幾乎相同
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but slightly different sets of 23 chapters.
卻又有些微差異的23章。
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The tiny variations are what makes each person different.
這些微差異就造成了人與人之間的不同。
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It's estimated that all the chapters together
如果把所有的章節都列入計算
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hold about 20,000 individual instructions, called genes.
大約會有兩萬筆說明,也就是基因。
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Written out, all those 20,000 instructions
如果把這兩萬筆說明全部寫下來
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are 30 million letters long!
會長達三千萬個字母!
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If someone were writing one letter per second,
如果人可以一秒鐘寫一個字母,
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it would take them almost an entire year to write it once.
那也需要花將近一年才能寫完一次。
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It turns out that our genome book is much, much longer
然而,我們的說明書比
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than just those 30 million letters,
三千萬個字母還長出許多—
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almost 100 times longer!
將近是它的一百倍!
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What are all those extra pages for?
那這些多餘的書頁又寫了些什麼呢?
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Well, each page of instructions has a few pages of nonsense inserted
嗯,每部份的說明都會插入幾頁無意義的編碼。
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that have to be taken out before we end up with something useful.
我們必須先將這些亂碼移除才能看到有意義的資訊。
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The parts we throw out, we call introns.
這部份我們移除的亂碼被稱為內插子。
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The instructions we keep, we call exons.
而保留下來的資訊被稱為外顯子。
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We can also have hundreds of pages in between each gene.
我們的基因與基因之間也可能有幾百頁的亂碼。
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Some of these excess pages were inserted
有些是在我們的祖先被病毒感染時
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by nasty little infections in our ancestors,
所插入的多餘頁面。
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but some of them are actually helpful.
但也有些看似無意的頁面是有用的。
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They protect the ends of each chapter from being damaged,
它們可以保護章節的頭尾免於破壞,
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or some help our cells find a particular thing they are looking for,
或當作索引,
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or give a cell a signal to stop making something.
也有可能是當作停止製造的訊號。
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All in all, for every page of instructions
總而言之,在每部份說明中
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there is almost 100 pages of filler.
大約包含了一百頁的內容。
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In the end, each of our books' 46 chapters
最後,我們書的 46 章
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is between 48 and 250 million letters long.
會介於 4.8 千萬到 2.5 億個字母長。
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That's 3.2 billion letters total!
共計三十二億個字母!
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To type all that copy, you would be at it for over 100 years,
若以打字方式複製,你需要花上一百年,
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and the book would be over 600,000 pages long.
而且這本書會超過六十萬頁。
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Every type of cell carries the same book,
每一種細胞都帶有相同的說明書,
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but each has a set of bookmarks that tell it exactly
但是會有不同的索引幫助搜尋
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which pages it needs to look up.
它們需要看的頁面。
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So a bone cell reads only the set of instructions it needs to become bone.
所以骨細胞只會看和生成骨頭相關的指引。
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Your brain cells,
你的腦細胞
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they read the set that tells them how to become brain.
會閱讀組成大腦所需的部份。
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If some cells suddenly decide to start reading other instructions,
如果一個細胞突然開始閱讀其他的指引
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they can actually change from one type to another.
他們就可以從一種細胞轉換成另一種。
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So every little cell in your body is holding on to an amazing book,
你身體裡每一個細胞都帶著這本神奇的書,
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full of the instructions for life.
這本書充滿對生命所有的註解。
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Your nose reads nose pages,
你的鼻子閱讀關於鼻子的部份,
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your toes read toes pages,
你的腳趾則閱讀關於腳趾的部份,
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and that little thing in the back of your throat,
而你喉嚨深處的那個小東西
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it's got its own pages too.
也有屬於自己的章節。
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They are under uvula.
就是標示「懸雍垂」的那幾頁。