首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
"I have great confidence that by the end of the decade we’ll know in vast detail how cancer cells arise," says microbiologist Ro
"I have great confidence that by the end of the decade we’ll know in vast detail how cancer cells arise," says microbiologist Ro
admin
2015-12-01
48
问题
"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 Hayward. 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."
Oncogenes are cancer-causing genes______.
选项
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
答案
B
解析
从第3段第2句话可知:70年代初,研究者们取得了重大进展,当时他们发现,在正常细胞中,致癌基因并不活跃。从宇宙射线辐射到饮食的任何东西都可能激活休眠的致癌基因,但如何激活仍然不为人知。如果一些致癌基因被激活,而细胞不能消灭他们,细胞就会变成癌细胞,可知B为正确答案。A、C、D项均不正确。
转载请注明原文地址:https://kaotiyun.com/show/DsGO777K
0
考博英语
相关试题推荐
Smallbusinessownersmustaccepttheburdensofentrepreneurship.Beinginbusinessforyour-selfrequiresyourfullattention
ThehistoryofAfrican-Americansduringthepast400yearsistraditionallynarrated【21】anongoingstraggleagainst【22】andindif
ThehistoryofAfrican-Americansduringthepast400yearsistraditionallynarrated【21】anongoingstraggleagainst【22】andindif
Oldpeoplearealwayssayingthattheyoungpeoplearenot【61】theywere.Thesamecommentis【62】fromgenerationtogenerationa
Duringthelastthirtyyears,theinternationaleconomyhasexperiencedabasicchange.ImprovementsintheInternetandotherc
Ican’tunderstandhowhecanfeelthathiscolleaguesarealwaysreadytodenouncehim.
(中国矿业大学2006年试题)Generally,acomputerisanydevicethatcanperformnumericalcalculations.Currently,【1】,thetermusually
Weareto______10,000,000computersnextyeartomeetthemarketrequirements.
Hedidnottellhisparentsbecauseheknewtheywouldtrytochangehismindbuthe______inacolleagueatwork.
Tight-lippedeldersusedtosay,"It’snotwhatyouwantinthisworld,butwhatyouget."Psychologyteachesthatyoudogetwh
随机试题
A.间脑B.大脑半球C.桥脑D.延脑E.中脑昏迷时瞳孔极度扩大,脑损害水平定位在
A.圆三角形B.椭圆形C.钝圆角梯形D.四边形E.圆形下列牙齿的开髓洞形呈下颌磨牙
恶性程度最高的乳癌类型是
A.范德华力B.疏水性相互作用C.离子-偶极、偶极-偶极D.氢键E.电荷转移复合物抗疟药氯喹与疟原虫的DNA碱基对之间形成()。
短期政府债券具有违约风险小,流动性强、收入免税等特点。()
()是把课程计划付诸实践的过程,是达到预期课程目标的基本途径。
选择最恰当的一项填充空缺处,使之符合原图表的排列规律,此项是()。
Beesareinsects.TheyliveallovertheWorldexceptWhereitisverycold.Beesdonotlikeiceandsnow.Theyaretheonlyins
Whodidthemanspeakwiththisafternoon?
春节是中国最重要的节日。观看春节联欢晚会(theSpringFestivalGala)是中国人庆祝春节的一个重要组成部分。这个一年一度的晚会由中央电视台(CCTV)直播,从除夕之夜晚上8点开始,持续约4个小时。晚会节目丰富多彩,以音乐、舞蹈、喜剧和戏
最新回复
(
0
)