對于托福閱讀素材的積累，一方面是提高對于英文的敏感以及熟練，其次也是培養(yǎng)自己的語感，那么下面就和出國留學(xué)網(wǎng)的小編一起來看看托福閱讀素材：一切始于一個(gè)細(xì)胞。
Unruly origins
Beginnings， and how to spot them
It all starts with a single cell
放肆的開端
開端，以及如何發(fā)現(xiàn)它們
一切都開始于一個(gè)細(xì)胞
DIANE MILLEY， a teacher， remembers getting the small， dry cough just before school broke up（詞匯）for the summer in 2013. She wasn’t worried： she considered herself generally healthy—she ran three times a week and went to the gym. Her doctor in Bradford， Massachusetts， put her on a course of antibiotics. When they didn’t work she had an X-ray. It showed nodules（詞匯）across her lungs. A bronchoscopy（詞匯）was ordered to retrieve a tissue sample（詞匯） from her lung. As she came round from the anaesthetic she remembers overhearing two medical staff talking. One said “It’s malignant.” She had late-stage lung cancer.戴安·米莉（Diane Milley）是一名教師。她記得2013年夏天學(xué)校臨放假前，她開始輕微的干咳。她并沒有放在心上——她覺得自己總體上很健康，每周跑步三次還去健身房。馬薩諸塞州布拉德福德的醫(yī)生對她用了一個(gè)療程的抗生素。治療無效后她拍了一張X光片，顯示她的肺部存在結(jié)節(jié)。隨后醫(yī)生讓她做支氣管鏡檢查，從她的肺部提取組織樣本。當(dāng)她從麻醉中醒來時(shí)，聽到兩名醫(yī)務(wù)人員在說話。其中一人說：“是惡性的?！彼嫉氖峭砥诜伟?。
Ms Milley’s body， like all human bodies， contained tens of trillions of copies of her genome. In theory， all those copies should be more or less the same. In practice， over the years， they all get knocked around（句型） in different ways. The oxygen that powers cell metabolism（詞匯）damages the DNA on which the genes are stored as a matter of course； so do background radiation and exposure to the many low-level carcinogens（詞匯）； so do sunlight and infection with viruses； so do choices about diet and recreational drugs（詞匯）， notably alcohol and tobacco （from which Ms Milley abstained）.和所有人的身體一樣，米莉的身體也含有自身基因的數(shù)十萬億個(gè)副本。理論上說，所有這些副本都應(yīng)該是基本相同的。然而實(shí)際上，經(jīng)年累月，它們以不同的方式遭到了破壞。為細(xì)胞代謝提供能量的氧會自然而然地破壞存儲基因的DNA，背景輻射和接觸許多低級致癌物也會如此，日曬和病毒感染也會如此，飲食選擇和娛樂性藥物，特別是酒精和煙草（米莉均不沾），也會如此。
The vast bulk of（句型）this damage is quickly fixed by DNA-repair enzymes； fewer than one mutation in a thousand persists. But wear and tear builds up. Many such changes make little or no difference. A few will be of consequence to（句型）the cell concerned， reducing or eliminating its capacity to do its job. But the loss of a single cell’s contribution matters not a jot.絕大多數(shù)此類損害都很快被DNA修復(fù)酶修復(fù)了；一千個(gè)突變中只有不到一個(gè)會留存下來。但這種損耗會累積。很多此類變化都無足輕重，少數(shù)則會影響相關(guān)細(xì)胞，降低或完全消除其履行職責(zé)的能力。但損失一個(gè)細(xì)胞的貢獻(xiàn)造成的影響微不足道。
There are some genes， though， where uncorrected damage can matter a lot. Foremost are the genes which control cell growth， such as HER2， which tells the cell how to make a protein called human epidermal-growth-factor receptor type 2. This is a protein that， when it sees a particular hormone， tells the cell it is in to divide. Mutations in the HER2 gene can make cells proliferate when there is no need. When they do so their daughter cells， which will share that HER2 mutation， will go on to do the same.然而，對于某些基因而言，未經(jīng)修復(fù)的損害可能就大有關(guān)系了。首先是那些控制細(xì)胞生長的基因，如HER2，它告訴細(xì)胞如何生成一種名為人類表皮生長因子（詞匯）受體2的蛋白質(zhì)。這種蛋白質(zhì)在遇到某種特定的激素時(shí)會指示它所在的細(xì)胞進(jìn)行分裂。HER2基因的突變可能導(dǎo)致細(xì)胞在毫無必要的時(shí)候增殖 。如果發(fā)生這種情況，其擁有同樣HER2突變（詞匯）的子細(xì)胞也會繼續(xù)做同樣的事情。
Among some 20，000 genes in the genome there are dozens which， like HER2， can cause unwanted cell division when they go wrong. To forestall such problems there are various tumour-suppressor genes whose job is to make sure that cells damaged in this way shut themselves down. The best known is the gene for a protein called p53， which stops cells from reproducing if their DNA is damaged. But these tumour-suppressor genes， too， are subject to mutation.在基因組中的大約20，000個(gè)基因中，有幾十個(gè)基因會像HER2一樣，在出錯(cuò)時(shí)可能引起有害的細(xì)胞分裂。為了預(yù)防這類問題，身體里還有各種各樣的腫瘤抑制基因，確保遭到此類損傷的細(xì)胞會自行關(guān)閉。最著名的是一種名為p53的蛋白質(zhì)的基因，它可以阻止DNA遭損壞的細(xì)胞自我復(fù)制。但是，這些腫瘤抑制基因也可能（句型）發(fā)生突變。
The numbers game
Thus over time， as genetic damage accumulates， the likelihood rises that somewhere in the body’s trillions of cells there is one that has， through five or six mutations in key genes， developed the ability to grow without check. This likelihood is not the same for everyone. Some people start off with quirks in their genome which make them more susceptible. Take the genes BRCA1 and BRCA2， which describe proteins that repair DNA； people who inherit a damaged version of one or the other face a higher risk of cancer （in particular， breast and ovarian cancer） because， with one crucial function already compromised， it takes fewer mutations for a tumour to get going.
數(shù)字游戲
因此，隨著時(shí)間的推移和基因損傷的累積，在身體里的數(shù)萬億個(gè)細(xì)胞中，有一個(gè)細(xì)胞因?yàn)殛P(guān)鍵基因發(fā)生了五六次突變而能夠無拘無束生長（句型，貶義）的可能性就變大了。這種可能性并不是人人平等的。有些人的基因組一開始就有些怪異，這讓他們更容易受到影響。拿基因BRCA1和BRCA2來說吧，它們表達(dá)的是用于修復(fù)DNA的蛋白質(zhì)。如果一個(gè)人繼承的其中一個(gè)基因受損，就會面臨更高的患癌風(fēng)險(xiǎn) （特別是乳腺癌和卵巢癌）。這是因?yàn)椋热灰粋€(gè)關(guān)鍵功能已經(jīng)受損（詞匯，手表翻譯no compromise永不磨損），那么只需要更少的突變就可發(fā)生腫瘤。
Once a cancer has begun its unruly growth it will pick up more and more mutations： the cancer genome project at the Sanger Institute， outside Cambridge in England， has found that cancers can have as few as ten mutations or as many as a few hundred. Though all the cells in the cancer are descended from one parent cell， they become increasingly diverse over time. Some cells come loose and start new tumours of their own elsewhere. The body’s immune system will often recognise that something is amiss and try to fight the cancer and slow its spread. Sometimes it wins， stopping the cancer or killing it. Sometimes it doesn’t.一旦腫瘤開始肆意生長（句型），它將會匯聚越來越多的突變。位于英國劍橋鎮(zhèn)外的桑格研究所（Sanger Institute）的癌癥基因組計(jì)劃發(fā)現(xiàn)，癌癥的突變數(shù)量少至十個(gè)，多達(dá)幾百個(gè)。雖然腫瘤的所有細(xì)胞都是一個(gè)親代細(xì)胞的子孫，但隨著時(shí)間的推移 ，它們變得越來越五花八門。一些細(xì)胞會松脫，到其他地方再自己開始生長新腫瘤。身體的免疫系統(tǒng)通常會發(fā)現(xiàn)有些東西不對了，并且試圖與癌癥斗爭并減緩其蔓延。有時(shí)它會贏，阻止甚至殺死癌癥。有時(shí)它不會。
When Ms Milley’s cancer was diagnosed all the things that could go wrong already had； the tumour was well developed and had spread through the lung and beyond. It would have been far better for her if it had been diagnosed earlier （see chart）. But with lung cancer， as with many other forms of the disease， there are often few symptoms until the disease is already at an advanced stage. If cancer could be reliably detected earlier， many lives might be saved.當(dāng)米莉確診患癌時(shí)，一切可能發(fā)生的糟糕情況都已發(fā)生：腫瘤發(fā)育完全，并擴(kuò)散到整個(gè)肺部和身體其他部分。如果能更早診斷出來，她的情況會好得多（見圖）。但是在肺癌以及許多其他類型的癌癥中，在發(fā)展到晚期（詞匯）之前通常不會有什么癥狀。如果我們能夠更早地、可靠地檢測到癌癥，也許能挽救許多生命。
In some wealthy countries， some cancers—for example， those of the breast， prostate and cervix—are regularly sought out before they start to cause symptoms. Now researchers are trying to improve diagnostic tools even further， so that more types of cancer can be found early on （and with greater reliability）. For some it is a terribly personal hunt. Billy Boyle， the president of a small biotech company， Owlstone Medical， based in Cambridge， in England， is one of them. He lost his wife Kate， mother to their two young boys， on Christmas morning in 2014. She died of colon cancer that had been picked up too late. Mr Boyle says that if colorectal cancer is detected early， 95% of sufferers survive. Only 6% survive if the cancer reaches stage four. For many cancers， early detection is “our greatest opportunity to improve survival，” says Mr Boyle.在一些富裕國家，人們會在出現(xiàn)癥狀之前定期篩查（句型）某些癌癥（例如乳腺癌、前列腺（詞匯）癌和宮頸（詞匯）癌）。如今研究人員正在努力進(jìn)一步改進(jìn)診斷工具，以便早日（并且以更高的可靠性）發(fā)現(xiàn)更多類型的癌癥。對于某些人來說，這樣的探索是源于極其個(gè)人化的經(jīng)歷。位于英國劍橋的小型生物技術(shù)公司Owlstone Medical的總裁比利·博伊爾（Billy Boyle）就是其中之一。2014年圣誕節(jié)的早晨 ，他失去了他的妻子、兩個(gè)小男孩的母親凱特。她死于結(jié)腸癌，發(fā)現(xiàn)時(shí)已經(jīng)太晚了。博伊爾說，如果結(jié)腸直腸癌能夠在早期發(fā)現(xiàn)，95%的患者能活下來。如果癌癥達(dá)到第四階段，生存率只剩6%。博伊爾說，對許多癌癥而言，早期監(jiān)測是“提高生存率的最大機(jī)會”。
Mr Boyle wants to detect cancer on the breath using an ion-mobility spectrometer—a gadget that weighs chemicals by passing them through an oscillating electric field. The breath contains a wide range of organic molecules that reflect what is going on in the body’s metabolism. Cancers， which affect the metabolism， should in so doing change the pattern of molecules on the breath. Although Owlstone’s system is very small—it fits on a chip the size of a coin—it is sensitive， identifying molecules at a level of a few parts per billion. The firm hopes that when it has identified molecular “fingerprints” associated with particular cancers it will be able to detect the disease earlier than other tests do.博伊爾想要使用離子遷移光譜儀（一種讓化學(xué)物質(zhì)通過振蕩電場來稱重的小機(jī)器）來通過呼吸檢測癌癥。呼出的氣體中含有許多有機(jī)分子，反映了身體發(fā)生的新陳代謝。癌癥會影響新陳代謝，所以應(yīng)該也會改變呼出氣體中分子的模式。雖然Owlstone公司的系統(tǒng)非常小——可以裝在硬幣大小的芯片上——它卻十分敏感，可以在十億分之幾（詞匯）的水平上識別分子。該公司希望，在確定了與特定癌癥相關(guān)的分子“指紋”后，它將能夠比其他測試更早地檢測到癌癥。
Improved diagnostics can do more than pick up cancers sooner. They can also reveal the cancers’ weaknesses. Because cancer drugs work in different ways， some will do well against a tumour with one set of mutations but leave unscathed one that has become cancerous by some other pathway. Troy Cox， head of Foundation Medicine， a diagnostics company based in Cambridge， Massachusetts， says that in America 14 cancer drugs now have “companion diagnostics”—tests that show whether a cancer is likely to be susceptible to them or not. Ms Milley’s lung cancer， for example， turned out to harbour a mutation which meant she could be treated with a drug that targets that specific protein （see next section）.改進(jìn)后的診斷方法能做的還不只是更早地檢測出癌癥，它們也可以揭示癌癥的弱點(diǎn)。因?yàn)榘┌Y藥物的起效方式各有不同，有些很善于對付由一種突變引發(fā)的腫瘤，但對于通過其他途徑癌變的腫瘤卻束手無策。總部位于馬薩諸塞州劍橋市的基礎(chǔ)醫(yī)學(xué)公司（Foundation Medicine）的總裁特洛伊·考克斯（Troy Cox）表示，在美國，有14種癌癥藥物有了“伴隨診斷”，這種測試可以顯示個(gè)體的癌癥是否比較可能對藥物敏感。比如，米莉的肺癌被發(fā)現(xiàn)帶有（句型）一種突變，這意味著她可以用針對那種特定蛋白質(zhì)的藥物來治療。