I have great confidence that by the end of the decade we'll know in vast detail how cancer cells arise, says microbiologist Robert Weinberg, an expert on cancer. "But," he cautions, "some people have the idea that once one understands the causes, the cure will rapidly follow. Consider Pasteur, he discovered the causes of many kinds of infections, but it was fifty or sixty years before cures were available."
This year, 50 percent of the 910,000 people who suffer from cancer will survive at least five years. In the year 2000, the National Cancer Institute estimates, that figure will be 75 percent. For some skin cancers, the five-year survival rate is as high as 90 percent. But other survival statistics are still discouraging — 13 percent for lung cancer, and 2 percent for cancer of the pancreas.
With as many as 120 varieties in existence, discovering how cancer works is not easy. The researchers made great progress in the early 1970s, when they discovered that oncogenes, which are cancer-causing genes, are inactive in normal cells. Anything from cosmic rays to radiation to diet may activate a dormant oncogene, but how remains unknown. If several oncogenes are driven into action, the cell, unable to turn them off, becomes cancerous.
The exact mechanisms involved are still mysterious, but the likelihood that many cancers are initiated at the level of genes suggests that we will never prevent all cancers. "Changes are a normal part of the evolutionary process," says oncologist William Haywar. Environmental factors can never be totally eliminated; as Hayward points out, "We can't prepare a medicine against cosmic rays."
The prospects for cure, though still distant, are brighter.
First, we need to understand how the normal cell controls itself. Second, we have to determine whether there are a limited number of genes in cells which are always responsible for at least part of the trouble. If we can understand how cancer works, we can counteract its action.
1.The example of Pasteur in the passage is used to_______.
A.predict that the secret of cancer will be disclosed in a decade
B.indicate that the prospects for curing cancer are bright
C.prove that cancer will be cured in fifty to sixty years
D.warn that there is still a long way to go before cancer can be conquered
2.The author implies that by the year 2000,_______.
A.there will be a drastic rise in the five-year survival rate of skin-cancer patients
B.90 percent of the skin-cancer patients today will still be living
C.the survival statistics will be fairly even among patients with various cancers
D.there won't be a drastic increase of survival rate of all cancer patients
3.Oncogenes are cancer-causing genes_______.
A.that are always in operation in a healthy person
B.which remain unharmful so long as they are not activated
C.that can be driven out of normal cells
D.which normal cells can't turn off
4.The word "dormant" in the third paragraph most probably means_______.
A.dead B.ever-present C.inactive D.potential
5.It can be inferred that the severity of cancers can be ranked as_________.
A.skin cancer, lung cancer, pancreas cancer B.skin cancer, Pancreas cancer, lung cancer
C.lung cancer, skin cancer, pancreas cancer D.pancreas cancer, skin cancer, lung cancer
长难例句分析
［长难例句］The researchers made great progress in the early 1970s, when they discovered that oncogenes, which are cancer-causing genes, are inactive in normal cells.
［结构分析］本句中，主干是The researchers made great progress。when引导的是非限定性定语从句，修饰前面的时间。在这个定语从句中， that...cells是宾语从句，其中which are cancer-causing genes为非限定性定语从句，修饰oncogenes。
［参考译文］在20世纪70年代初，研究者们取得了重大进展，那时他们发现在普通细胞中，致癌基因并不活跃。
全文参考译文
“我深信，在本年代末，我们将对癌细胞的产生有更详细的了解。”微生物学家及癌症专家Robert Weinberg说。“但是，”他警告说，“有些人认为，一旦人们找到了病因，就会很快找到治疗办法。想一想Pasteur，他发现了许多传染病的起因，但是五六十年后才出现了治疗方法。”
今年，91万癌症患者中，50％的人至少可生存5年。国家癌症研究所估计，到2000年，这个数字将会是75％。对于一些皮肤癌患者，5年的生存率高达90％。但是其他生存统计数字仍令人失望——肺癌患者13％，胰腺癌患者2％。
由于存在着120多种不同的癌症，发现癌症的机理并不容易。在20世纪70年代初，研究者们取得了重大进展，那时他们发现在普通细胞中，致癌基因并不活跃。从宇宙射线辐射到饮食的任何东西都可能激活处于休眠状态的致癌基因，但如何维持这种状态还不为人知。如果一些致癌基因被激活，而细胞不能消灭它们，细胞就变成癌细胞。
包含其中的准确机理仍然是一个未知数。但是许多癌症起因于基因这一可能性，表明我们永远不能预防所有的癌症。“变化是进化过程的正常组成部分，”肿瘤学家William Haywar说。环境因素永远不可完全排除在外；正如他指出的那样，“我们无法准备一种对付宇宙射线的药物。”
治疗前景虽然还很遥远，但越加光明起来。
“首先，我们需要知道普通细胞是如何控制自己的。其次，我们必须确定细胞中是否有有限数量的基因经常成为癌症的起因或至少部分起因。如果我们知道了癌症发作机理，我们就能采取相应的措施。”
题目答案与解析
1.文中举用Pasteur的例子，是用来_________。
A.预言10年后癌症的秘密将被揭开 B.预示治疗癌症的前景是光明的
C.证明50～60年后癌症将被治愈 D.告诫在征服癌症之前还有很长的路要走
【答案】D
【解析】从第一段最后一句“想一想Pasteur吧，他发现了许多传染病病因，但是过了五六十年才有了治疗方法”，可知D项为正确答案。
2.作者暗示到2000年，______。
A.5年生存率的皮肤癌患者会有大幅度的增加
B.今天90％的皮肤癌病人仍然活着
C.各种癌症患者之间的生存率统计数字将会持平
D.所有癌症患者生存率不会有大的提高
【答案】D
【解析】本题为推断题。A、B、C项均不正确。D项正确。
3.致癌基因就是引起癌症的基因，它们_________。
A.总是活跃在健康人体内 B.只要不被激活，就不会有害
C.可以从正常细胞中驱赶出去 D.正常细胞无法排除
【答案】B
【解析】从第三段第二句意为：“20世纪70年代初，研究者们取得了很大进步，当时他们发现在正常细胞中，致癌基因并不活跃。从宇宙射线到辐射饮食等任何东西都可能激活休眠的致癌基因，但这一过程仍然不为人知。如果几个致癌基因被激活，而细胞不能将他们消灭，则会成为癌细胞。”从中可知B项为正确答案。
4.第三段中的单词“dormant”最有可能意味着_________。
A.死的 B.经常存在的 C.不活动的 D.潜在的
【答案】C
【解析】dormant：adj. 睡眠状态的，静止的，隐匿的。inactive：adj. 无行动的，不活动的，停止的，怠惰的，非活动的。可知答案为C项。
5.按照严重性程度，可以推理出癌症的顺序为_________。
A.皮肤癌，胰腺癌，肺癌 B.皮肤癌，肺癌，胰腺癌
C.肺癌，皮肤癌，胰腺癌 D.胰腺癌，肺癌，皮肤癌
【答案】D
【解析】从活过5年的癌症患者的比例来看，分别是皮肤癌90％，肺癌13％和胰腺癌2％，由此可以推理出来其严重程度。
