我們掃描了8,000人的DNA，以瞭解基因是如何影響面部特徵的

一項新的研究表明，人類DNA的130多個區域在塑造面部特徵中發揮了作用。鼻子是受基因影響最大的面部特徵。瞭解特定基因與面部特徵之間的聯絡對於治療面部畸形或牙齒矯正可能會有幫助。

你也許會認為基因決定臉部外貌這件事太明顯了，只要看一下家庭相簿就會發現，你的祖父母，堂兄兄妹，叔叔和阿姨都有相同的鼻子，眼睛或下巴。也許你已經見過或認識患有遺傳綜合症的人，導致這種病的起因就是一個或多個基因發生了破壞性的改變，其患者的面部特徵通常和普通人有著明顯的不同。

就在不久之前，遺傳學家都還搞不清楚我們DNA中到底哪一部分和我們面部的基本外形有關係，驚奇不驚奇？在這個看臉的世界裡，我們對DNA和外貌之間的關係的瞭解居然是如此之少，這真是讓人吃驚。現在由於有了海量的臉部影象以及對應的基因資訊，這個領域終於有了非常迅速的發展。

那麼我們對與面部容貌相關的遺傳學到底瞭解多少呢？我們能不能透過一個人的DNA可靠地預測這個人的臉長得什麼樣子？這些基因對一個人的健康和疾病會有什麼影響？我們這個研究團隊的成員都是人類學家和人類遺傳學家，我們的研究重點就是找出那些導致人類面部相同和不同的生物因素。

有多少基因與面部容貌有關？

對於這個問題，我們仍然沒有一個完整的答案，但我們的合作研究小組在《自然遺傳學》上發表的最新研究成果已經確定了130多個與面部形狀的某些特定部分相關的染色體區域。這是非常關鍵的第一步，它將幫助我們瞭解遺傳是如何影響我們的面孔容貌，以及掌握這些知識對人類的健康將來會有哪些影響。

我們掃描了8,000多個人的DNA，從3D面部影象得出了數十個形狀測量值，然後透過查詢大約700萬個遺傳標記（我們已經知道這部分的基因密碼是因人而異的）和形狀測量值之間的統計關係，從而找到影響面部容貌的那部分基因。

當我們發現面部特徵與一個或多個遺傳標記之間存在著統計關聯時，我們就可以在染色體上精確確定影響面部特徵的DNA區域，這樣這個區域周圍的基因就自然成了我們研究鼻子嘴唇等面部特徵的主要候選基因。如果我們從前已經對這些基因有一些瞭解，例如這個基因在胚胎中形成臉部時比較活躍，那麼我們就可以更加確定這個基因就是我們要找的基因。

雖然130多個染色體區域看起來很多，但我們很可能還只是接觸了皮毛，我們預期會有成千上萬個這樣的區域來決定人類面部的形狀，也就是說影響面部容顏的基因會有成千上萬。在這些染色體區域裡面許多基因其對容顏的影響是如此之小以至於我們可能永遠沒有足夠的統計能力來檢測它們。

我們對這些基因瞭解多少？

當我們整體地檢視這130多個和容顏相關的DNA區域時，我們發現了一些有趣的規律。

不管你是否喜歡，鼻子都是受基因影響最大的部分。也許不出你的所料，臉頰等部位受飲食等生活方式因素影響大，和遺傳的關​聯最少。

這些基因對面部形狀的影響方式各不相同，我們發現有些基因對臉部的影響非常區域性，其影響只限制在某些特定部位上，但另外有些基因的影響則非常廣泛，涉及到臉部的多個部位。

我們還發現，這些基因中有很大一部分都參與了人體的基本發育成長過程（例如，骨骼的形成），並且在許多情況下，這些基因也是與罕見綜合徵和麵部畸形（如顎裂）有關的基因。

我們發現有趣的是，涉及面部的基因和涉及四肢發育的基因之間存在著高度的重疊。我們知道許多遺傳綜合徵的特徵是手和麵部同時畸形，這個發現可能是進一步研究這些病症的一個重要線索。另一個奇怪的發現是，我們發現有一些證據表明，有些與面部形狀有關的基因也可能與癌症有關，這真是一個令人驚訝的發現，因為新出現的證據表明，接受過小兒癌症治療的患者會顯示出一些獨特的面部特徵。

有沒有人可能透過我的DNA來做出一張和我一模一樣的照片？

在今天或可預見的將來，不大可能會有人拿你的DNA樣品來構建出你的臉部影象。研究基因的特徵是一項非常艱鉅的任務，所以透過基因來預測一個人的面部模樣是非常困難的。

我們現在確定的130多個遺傳區域僅僅能解釋不到10％的面部形狀不同，這充分說明了想透過基因預測容貌會有多難。即使我們瞭解了與面部外觀有關的所有基因，預測容貌依然是一個巨大的挑戰，這是因為諸如面部形狀之類的複雜特徵不是透過簡單地總結一堆單個基因的作用就可以確定的，還有許多生物和非生物因素會影響到人的面部特徵，例如：年齡，飲食，氣候，激素，創傷，疾病，日曬，生物力學的作用和整形手術。

所有這些因素都以非常複雜的方式和我們的基因互相作用，而我們對這種複雜的互動方式目前還是一無所知。此外，基因之間還會發生稱之為“上位性”的基因-基因相互作用，這種作用的影響可能是非常複雜而且不可預測的，這進一步增加了透過基因預測容貌的複雜性。

這麼看來，現在還沒有研究人員能夠成功透過DNA來預測人的面部特徵就不奇怪了，當然這並不是說這樣的預測以後也永遠不可能，但是如果有人告訴你說現在他們就可以做到這一點，那你對這樣的人就應該馬上畫個大大的問號。

在開始閱讀英文原文之前，請先複習下列核心詞彙​：

scan - v. 掃描

facial - adj. 臉部的

feature - n. 特徵

control - v. 控制

gene - n. 基因

reveal - v. 揭示

influence - v. 影響

specific - adj. 特定的

geneticist - n. 遺傳學家

galling - adj. 讓人驚奇的

implication - n. 後果，影響

anthropologist - n. 人類學家

biological - adj. 生物的，生物學的

focus - v. 聚焦

statistical - adj. 統計的，統計學的

association - n. 關聯

chromosome - n. 染色體

embryo - n. 胚胎

chromosomal - adj. 染色體的

scratch - v. 撓，抓

scratch the surface - 僅僅觸及皮毛

syndrome - n. 綜合症

individual - n. 個人

pediatric - adj. 小兒科的

sample - n. 樣品

trait - n. 特徵，特質

context - n. 上下文，場景

to put sth in context - 透過特定的場景來理解

在複習了以上詞彙後，請將下面的英文原文一口氣讀完，不要在中途停下來去查那些不認識的單詞。有了上面的核心單詞打底，你完全可以將整篇文章讀完並且理解裡面的大致意思。記住，你只要做到大致明白就可以了。

閱讀能力和閱讀量成正比，要提高閱讀量，必須是大量的泛讀，如果要對每個不懂的單詞都去查字典，那麼就不可能透過大量的泛讀來提高你的閱讀量。

We scanned the DNA of 8,000 people to see how facial features are controlled by genes

Seth M. Weinberg, Associate Professor in the Departments of Oral Biology, Human Genetics, and Anthropology. Co-Director of the Center for Craniofacial and Dental Genetics, University of Pittsburgh and John R. Shaffer, Assistant Professor of Human Genetics, University of Pittsburgh

A new study reveals more than 130 regions in human DNA play a role in sculpting facial features.The nose is the facial feature most influenced by your genes.Understanding the link between specific genes and facial features could be useful for treating facial malformations or for orthodontics.

You might think it's rather obvious that your facial appearance is determined by your genes. Just look in the family photo album and observe the same nose, eyes or chin on your grandparents, cousins and uncles and aunts. Perhaps you have seen or know someone with a genetic syndrome – that often results from a damaging alteration to one or more genes – and noticed the often distinctive facial features.

You may be surprised to learn that until very recently, geneticists had virtually no understanding of which parts of our DNA were linked to even the most basic aspects of facial appearance. This gap in our knowledge was particularly galling since facial appearance plays such an important role in basic human interactions. The availability of large data sets combining genetic information with facial images that can be measured has rapidly advanced the pace of discovery.

So, what do we know about the genetics of facial appearance? Can we reliably predict a person's face from their DNA? What are the implications for health and disease? We are an anthropologist and a human geneticist whose research focuses on uncovering the biological factors that underlie the similarities and differences in facial appearance among humans.

How many genes are associated with facial appearance?

We still don't have a complete answer to this question, but recent work published in Nature Genetics by our collaborative research team has identified more than 130 chromosomal regions associated with specific aspects of facial shape. Identifying these regions is a critical first step toward understanding how genetics impacts our faces and how such knowledge could impact human health in the future.

We accomplished this by scanning the DNA of more than 8,000 individuals to look for statistical relationships between about seven million genetic markers – known locations in the genetic code where humans vary – and dozens of shape measurements derived from 3D facial images.

When we find a statistical association between a facial feature and one or more genetic markers, this points us to a very precise region of DNA on a chromosome. The genes located around that region then become our prime candidates for facial features like nose or lip shape, especially if we have other relevant information about their function – for example, they may be active when the face is forming in the embryo.

While more than 130 chromosomal regions may seem like a large number, we are likely only scratching the surface. We expect that thousands of such regions – and therefore thousands of genes – contribute to facial appearance. Many of the genes at these chromosomal regions will have such small effects, we may never have enough statistical power to detect them.

What do we know about these genes?

When we look collectively at the implicated genes at these 130-plus DNA regions, some interesting patterns emerged.

Your nose, like it or not, is the part of your face most influenced by your genes. Perhaps not surprisingly, areas like the cheeks, which are highly influenced by lifestyle factors like diet, showed the fewest genetic associations.

The ways that these genes influence facial shape was not at all uniform. Some genes, we found, had highly localized effects and impacted very specific parts of the face, while others had broad effects involving multiple parts.

We also found that a large proportion of these genes are involved in basic developmental processes that build our bodies – bone formation, for example – and, in many cases, are the same genes that have been implicated in rare syndromes and facial anomalies like cleft palate.

We found it interesting that there was a high degree of overlap between the genes involved in facial and limb development, which may provide an important clue as to why many genetic syndromes are characterized by both hand and facial malformations. In another curious twist, we found some evidence that the genes involved in facial shape may also be involved in cancer – an intriguing finding given emerging evidence that individuals treated for pediatric cancer show some distinctive facial features.

Can someone take my DNA and construct an accurate picture of my face?

It is unlikely that today, or for the foreseeable future, someone could take a sample of your DNA and use it to construct an image of your face. Predicting an individual's facial appearance, like any complex genetic trait, is a very difficult task.

To put that statement in context, the 130-plus genetic regions we identified explain less than 10% of the variation in facial shape. However, even if we understood all of the genes involved in facial appearance, prediction would still be a monstrous challenge. This is because complex traits like facial shape are not determined by simply summing up the effects of a bunch of individual genes. Facial features are influenced by many biological and non-biological factors: age, diet, climate, hormones, trauma, disease, sun exposure, biomechanical forces and surgery.

All of these factors interact with our genome in complex ways that we have not even begun to understand. To add to this picture of complexity, genes interact with one another; this is known as "epistasis," and its effects can be complex and unpredictable.

It is not surprising then, that researchers attempting to predict individual facial features from DNA have been unsuccessful. This is not to say that such prediction will never be possible, but if someone is telling you they can do this today, you should be highly skeptical.