对于托福阅读素材的积累，一方面是提高对于英文的敏感以及熟练，其次也是培养自己的语感，那么下面就和出国留学网的小编一起来看看托福阅读素材：一切始于一个细胞。
Unruly origins
Beginnings， and how to spot them
It all starts with a single cell
放肆的开端
开端，以及如何发现它们
一切都开始于一个细胞
DIANE MILLEY， a teacher， remembers getting the small， dry cough just before school broke up（词汇）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（词汇）across her lungs. A bronchoscopy（词汇）was ordered to retrieve a tissue sample（词汇） 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）是一名教师。她记得2013年夏天学校临放假前，她开始轻微的干咳。她并没有放在心上——她觉得自己总体上很健康，每周跑步三次还去健身房。马萨诸塞州布拉德福德的医生对她用了一个疗程的抗生素。治疗无效后她拍了一张X光片，显示她的肺部存在结节。随后医生让她做支气管镜检查，从她的肺部提取组织样本。当她从麻醉中醒来时，听到两名医务人员在说话。其中一人说：“是恶性的。”她患的是晚期肺癌。
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（词汇）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（词汇）； so do sunlight and infection with viruses； so do choices about diet and recreational drugs（词汇）， notably alcohol and tobacco （from which Ms Milley abstained）.和所有人的身体一样，米莉的身体也含有自身基因的数十万亿个副本。理论上说，所有这些副本都应该是基本相同的。然而实际上，经年累月，它们以不同的方式遭到了破坏。为细胞代谢提供能量的氧会自然而然地破坏存储基因的DNA，背景辐射和接触许多低级致癌物也会如此，日晒和病毒感染也会如此，饮食选择和娱乐性药物，特别是酒精和烟草（米莉均不沾），也会如此。
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.绝大多数此类损害都很快被DNA修复酶修复了；一千个突变中只有不到一个会留存下来。但这种损耗会累积。很多此类变化都无足轻重，少数则会影响相关细胞，降低或完全消除其履行职责的能力。但损失一个细胞的贡献造成的影响微不足道。
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，对于某些基因而言，未经修复的损害可能就大有关系了。首先是那些控制细胞生长的基因，如HER2，它告诉细胞如何生成一种名为人类表皮生长因子（词汇）受体2的蛋白质。这种蛋白质在遇到某种特定的激素时会指示它所在的细胞进行分裂。HER2基因的突变可能导致细胞在毫无必要的时候增殖 。如果发生这种情况，其拥有同样HER2突变（词汇）的子细胞也会继续做同样的事情。
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.在基因组中的大约20，000个基因中，有几十个基因会像HER2一样，在出错时可能引起有害的细胞分裂。为了预防这类问题，身体里还有各种各样的肿瘤抑制基因，确保遭到此类损伤的细胞会自行关闭。最著名的是一种名为p53的蛋白质的基因，它可以阻止DNA遭损坏的细胞自我复制。但是，这些肿瘤抑制基因也可能（句型）发生突变。
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.
数字游戏
因此，随着时间的推移和基因损伤的累积，在身体里的数万亿个细胞中，有一个细胞因为关键基因发生了五六次突变而能够无拘无束生长（句型，贬义）的可能性就变大了。这种可能性并不是人人平等的。有些人的基因组一开始就有些怪异，这让他们更容易受到影响。拿基因BRCA1和BRCA2来说吧，它们表达的是用于修复DNA的蛋白质。如果一个人继承的其中一个基因受损，就会面临更高的患癌风险 （特别是乳腺癌和卵巢癌）。这是因为，既然一个关键功能已经受损（词汇，手表翻译no compromise永不磨损），那么只需要更少的突变就可发生肿瘤。
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.一旦肿瘤开始肆意生长（句型），它将会汇聚越来越多的突变。位于英国剑桥镇外的桑格研究所（Sanger Institute）的癌症基因组计划发现，癌症的突变数量少至十个，多达几百个。虽然肿瘤的所有细胞都是一个亲代细胞的子孙，但随着时间的推移 ，它们变得越来越五花八门。一些细胞会松脱，到其他地方再自己开始生长新肿瘤。身体的免疫系统通常会发现有些东西不对了，并且试图与癌症斗争并减缓其蔓延。有时它会赢，阻止甚至杀死癌症。有时它不会。
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.当米莉确诊患癌时，一切可能发生的糟糕情况都已发生：肿瘤发育完全，并扩散到整个肺部和身体其他部分。如果能更早诊断出来，她的情况会好得多（见图）。但是在肺癌以及许多其他类型的癌症中，在发展到晚期（词汇）之前通常不会有什么症状。如果我们能够更早地、可靠地检测到癌症，也许能挽救许多生命。
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.在一些富裕国家，人们会在出现症状之前定期筛查（句型）某些癌症（例如乳腺癌、前列腺（词汇）癌和宫颈（词汇）癌）。如今研究人员正在努力进一步改进诊断工具，以便早日（并且以更高的可靠性）发现更多类型的癌症。对于某些人来说，这样的探索是源于极其个人化的经历。位于英国剑桥的小型生物技术公司Owlstone Medical的总裁比利·博伊尔（Billy Boyle）就是其中之一。2014年圣诞节的早晨 ，他失去了他的妻子、两个小男孩的母亲凯特。她死于结肠癌，发现时已经太晚了。博伊尔说，如果结肠直肠癌能够在早期发现，95%的患者能活下来。如果癌症达到第四阶段，生存率只剩6%。博伊尔说，对许多癌症而言，早期监测是“提高生存率的最大机会”。
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.博伊尔想要使用离子迁移光谱仪（一种让化学物质通过振荡电场来称重的小机器）来通过呼吸检测癌症。呼出的气体中含有许多有机分子，反映了身体发生的新陈代谢。癌症会影响新陈代谢，所以应该也会改变呼出气体中分子的模式。虽然Owlstone公司的系统非常小——可以装在硬币大小的芯片上——它却十分敏感，可以在十亿分之几（词汇）的水平上识别分子。该公司希望，在确定了与特定癌症相关的分子“指纹”后，它将能够比其他测试更早地检测到癌症。
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）.改进后的诊断方法能做的还不只是更早地检测出癌症，它们也可以揭示癌症的弱点。因为癌症药物的起效方式各有不同，有些很善于对付由一种突变引发的肿瘤，但对于通过其他途径癌变的肿瘤却束手无策。总部位于马萨诸塞州剑桥市的基础医学公司（Foundation Medicine）的总裁特洛伊·考克斯（Troy Cox）表示，在美国，有14种癌症药物有了“伴随诊断”，这种测试可以显示个体的癌症是否比较可能对药物敏感。比如，米莉的肺癌被发现带有（句型）一种突变，这意味着她可以用针对那种特定蛋白质的药物来治疗。
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