identical twins originate from the same DNA,

同卵雙生子始於相同的DNA

so how can they turn out so different

那他們為何成長得如此不同

even in traits that have a significant genetic component?

甚至在特徵上有一個顯著遺傳成份？

For instance, why might one twin get heart disease at 55,

舉例來說，為什麼雙胞胎中的一位可能在55歲得到心臟病

while her sister runs marathons in perfect health?

同時她的姐妹在完美健康狀態下跑馬拉松

Nature versus nurture has a lot to do with it,

先天與後天之間有很大的關係

but a deeper related answer can be found within something called epigenetics.

但一個更深層相關的答案可以在表徵基因中找到

That's the study of how DNA interacts

就是研究DNA之間如何互相作用

with the multitude of smaller molecules found within cells,

在細胞中有許多的小分子

which can activate and deactivate genes.

能夠活化和不活化基因

If you think of DNA as a recipe book,

你把DNA想成一本食譜

those molecules are largely what determine what gets cooked when.

這些分子主要決定取得什麼、什麼時候煮

They aren't making any conscious choices themselves,

它們並沒有任何意識的選擇它們自己

rather their presence and concentration within cells makes the difference.

當然它們的存在和集中在細胞中讓它們有所不同

So how does that work?

所以它是如何運作的

Genes in DNA are expressed when they're read and transcribed into RNA,

在DNA中的基因，當它們被讀取和轉錄成RNA時可以被表示

which is translated into proteins by structures called ribosomes.

RNA被轉化為結構蛋白質稱為核糖體

And proteins are much of what determines a cell's characteristics and function.

而蛋白質決定一個細胞的特性和功能

Epigenetic changes can boost or interfere with the transcription of specific genes.

後天的改變能提高或干擾特殊基因的錄製

The most common way interference happens is that DNA,

最常見發生的干擾方式就是DNA

or the proteins it's wrapped around,

或蛋白質，它被DNA纏繞

gets labeled with small chemical tags.

貼上一些小的化學標籤

The set of all of the chemical tags that are attached to the genome

一整個全部的化學標籤，貼上到基因組

of a given cell

在一個被給定的細胞

is called the epigenome.

這被稱為表徵基因組

Some of these, like a methyl group, inhibit gene expression

這些，像一個甲基群禁止基因用RNA表示

by derailing the cellular transcription machinery

藉由使細胞轉錄機制脫軌

or causing the DNA to coil more tightly,

或促使DNA被纏繞的更緊密

making it inaccessible.

讓它難以進入

The gene is still there, but it's silent.

基因還是存在那邊，但它是沉默的

Boosting transcription is essentially the opposite.

提高轉錄效率，實質上是相反的

Some chemical tags will unwind the DNA, making it easier to transcribe,

一些化學標籤將解開DNA讓它更容易轉錄

which ramps up production of the associated protein.

提升相關的蛋白質生成

Epigenetic changes can survive cell division,

表徵基因改變能逃過細胞分裂

which means they could affect an organism for its entire life.

這意謂著他們能影響一個有機體的整個生命

Sometimes that's a good thing.

有時候這是件好事

Epigenetic changes are part of normal development.

表徵基因改變是正常發展的一部份

The cells in an embryo start with one master genome.

細胞從一個帶有主要的基因組胚胎開始

As the cells divide, some genes are activated

當細胞在分裂，一些基因會被啟動

and others inhibited.

而其它的會禁止

Over time, through this epigenetic reprogramming,

隨著時間，憑著這個表徵基因的重新編譯

some cells develop into heart cells,

一些細胞發展成心臟細胞

and others into liver cells.

其它的成為肝臟細胞

Each of the approximately 200 cell types in your body

在你的身體中大約有二百多種細胞

has essentially the same genome

實際上擁有相同的基因組

but its own distinct epigenome.

但是它擁有它獨特的表徵基因組

The epigenome also mediates a lifelong dialogue

表徵基因組也居中協調終生的對話

between genes and the environment.

在基因和環境之中

The chemical tags that turn genes on and off

化學標籤能夠開啟和關閉基因

can be influenced by factors including diet,

能被影響的因素包括節食

chemical exposure,

化學暴露

and medication.

和藥物治療

The resulting epigenetic changes can eventually lead to disease,

表徵基因改變的結果最終導致疾病發生

if, for example, they turn off a gene that makes a tumor-suppressing protein.

舉例來說，如果它們關閉一個基因，將產生一個腫瘤壓制蛋白

Environmentally-induced epigenetic changes are part of the reason

環境引起的表徵基因改變是一部份原因

why genetically identical twins can grow up to have very different lives.

為何從遺傳學角度的同卵雙生子能成長成非常不同的生命

As twins get older, their epigenomes diverge,

當雙胞長大，他們的表徵基因組分歧

affecting the way they age and their susceptibility to disease.

影響它們的年紀和對他們對疾病感受性

Even social experiences can cause epigenetic changes.

甚至社交經驗也能改變表徵基因

In one famous experiment,

在一個知名的實驗

when mother rats weren't attentive enough to their pups,

當鼠媽不留心它們的小孩

genes in the babies that helped them manage stress were methylated

在嬰兒中的基因，幫助他們管理壓力的是甲醇化物

and turned off.

然後關掉它

And it might not stop with that generation.

而它可能不會隨著世代

Most epigenetic marks are erased when egg and sperm cells are formed.

當卵子和精子細胞被形成，大多數的表徵基因記號被消除

But now researchers think that some of those imprints survive,

但是現在的研究院想說，會有一些印記留存下來

passing those epigenetic traits on to the next generation.

經過這些表徵基因特性給了下一代

Your mother's or your father's experiences as a child,

你的媽媽或爸爸的經歷過做為一個孩子

or choices as adults,

或成人一般的選擇

could actually shape your own epigenome.

能實際形塑屬於你的表徵基因組

But even though epigenetic changes are sticky,

但是即使表徵基因改變是麻煩的

they're not necessarily permanent.

他們不必是永久性的

A balanced lifestyle that includes a healthy diet,

一個均衡的生活方式包括一個健康的飲食

exercise,

運動

and avoiding exposure to contaminants

和避免暴露在污染物之中

may in the long run create a healthy epigenome.

可能從長遠來看，能創造出一個健康的表徵基因組

It's an exciting time to be studying this.

能夠去研究這個是個令人激動的時刻

Scientists are just beginning to understand

科學家們才開始瞭解

how epigenetics could explain mechanisms of human development and aging,

如何用表徵基因能說明人類成長和老化的機制

as well as the origins of cancer,

如同癌症中的有機體

heart disease,

心臟病

mental illness,

精神疾病

addiction,

成癮

and many other conditions.

和其它許多可能的情況

Meanwhile, new genome editing techniques are making it much easier

同時，一個新的基因組編輯技術讓這個更加容易

to identify which epigenetic changes really matter for health and disease.

去分辦哪些表徵基因改變真的和健康和疾病有關

Once we understand how our epigenome influences us,

當我們瞭解我們的表徵基因組如何影響我們

we might be able to influence it, too.

我們也可能去影響它