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
考研
Cancer arises when the descendants of just one of our more than ten thousand billion cells proliferate out of control, eventuall
Cancer arises when the descendants of just one of our more than ten thousand billion cells proliferate out of control, eventuall
admin
2015-03-25
74
问题
Cancer arises when the descendants of just one of our more than ten thousand billion cells proliferate out of control, eventually interfering with normal body functions. Since so many cells are at risk, the most amazing thing about cancer to me is how many years it usually takes to develop the disease. One major obstruction to the proliferation of cancerous cells is the phenomenon of
apoptosis
, which causes nearly all of our cells to kill themselves whenever they start to behave aberrantly.
A complicated cellular signaling network determines the balance between the pro-apoptotic and anti-apoptotic proteins inside animal cells. Each of our many cells is constantly sensing its external and internal environment and will sacrifice itself(for our own good)if it is either not correctly located or not behaving normally. Without mechanisms of this type, the evolution of large complex organisms such as ourselves would probably not have been possible, because the tumors caused by cancerlike diseases would have overtaken us early in life.
Tumors arise after a long process of random mutation followed by multiple rounds of selection for those cells able to proliferate best. One change selected for is in apoptotic mechanisms, which will be altered in different ways in different tumors. Imagine that we could determine why the cells in an individual’s tumor incorrectly compute that they need not kill themselves, as normal cells would do in their condition. If we understood the fundamental mechanisms by which cells make these decisions, we would stand an excellent chance of creating a tailored mixture of drugs that causes the tumor cells to compute differently, so that they commit suicide without harming normal cells.
Another promising strategy takes advantage of the fact that essentially all cancer cells have acquired a defect in some aspect of their "DNA metabolism" , often some aspect of DNA repair that causes them to become highly mutable. This genetic instability of cancer cells is selected for early in tumor development, because only such cells can evolve the multiple additional changes, including defects in apoptosis, that are necessary for most cell types to become malignant.
Cells that are too genetically unstable will die. Therefore, a treatment that blocks a particular DNA repair process can be lethal for a cancer cell, while sparing normal cells. If we could determine why the cells in a particular individual tumor are genetically unstable, we might be able to design drugs that kill the cells in that cancer highly selectively, with little harm to normal cells.
These examples of rational approaches to cancer therapy were only a dream until recently. But by targeting these types of alterations in cancer cells, researchers have made impressive progress and are thus much closer to being able to design highly selective therapies based on the critical molecular defects in an individual tumor. But for most tumors, this type of approach is still hit or miss, because oncologists are severely hampered by an inadequate understanding of the fundamental processes that are altered in a particular tumor.
The word "apoptosis"(Line 5, Para.1)most probably means
选项
A、appearing.
B、changing.
C、dying.
D、thriving.
答案
C
解析
语义理解题。根据题干提示从第一段找到apoptosis出现的语境。在apoptosis出现的下文有定语从句“该现象会造成所有这些细胞每当表现异常时就自杀”对apoptosis进行修饰。据此可以推测出该词跟kill有关,与此相符的只有[C]dying。
转载请注明原文地址:https://kaotiyun.com/show/hU74777K
0
考研英语一
相关试题推荐
MosttownsuptoElizabethantimesweresmallerthanamodernvillage,andeachofthemwasbuilta-rounditsweeklymarketwher
Manypeopleconsiderthewideruseofbiofuelsapromisingwayofreducingtheamountofsurpluscarbondioxide(C02)beingpump
ItisgenerallybelievedthatthedigitaldivideissomethingTheauthorseemstobelievethatwidenedwagegapcanbeattribut
EverysecondintheUnitedStatesalone,morethan250animalsareslaughteredforfood,addinguptomorethan8billionanimal
Whenwomendobecomemanagers,dotheybringadifferentstyleanddifferentskillstothejob?Aretheybetter,orworse,manag
DepressionAstudyledbyresearchersattheUniversityofPennsylvaniaindicatesthattheantidepressantsworknobetterth
DoesEconomicRecessionandDivorceRatehaveSomethingRelated?"Ah,yes,divorce",RobinWilliamsoncemused,"fromtheL
Themostnoticeabletrendamongmediacompaniesisverticalintegration—anattempttocontrolseveralrelatedaspectsofthem
TopbusinesschiefslikeIndraNooyi,AnuAghaandShikhaSharmamayhavebrokentheglassceilingtocommandtheirownboardroo
Oneofthemosteminentofpsychologists,ClarkHull,claimedthattheessenceofreasoningliesintheputtingtogetheroftwo
随机试题
随着经济社会发展和物质消费水平大幅提高,我国生活垃圾产生量迅速增长,环境隐患日益突出,已经成为新型城镇化发展的制约因素。实施生活垃圾分类(garbagesorting),可以有效改善城乡环境,促进资源回收利用,提高城镇化质量。垃圾分类是
某县氮肥厂每年生产氨5000t,全部用来生产NH4HCO3,问每年可生产NH4HCO3多少吨?若全部用来生产CO(NH2)2,则可生产多少吨?
A、Becauseitwastooheavy.B、Becauseitdidnotbendeasily.C、Becauseitdidnotshootfar.D、Becauseitsstringwasshort.C
刘某,男,46岁,患胃病10年,时发时止。近1月来胃痛隐隐,饥则尤甚,劳则加剧,喜温喜按,泛吐清水,纳谷不香,大便溏薄,完谷不化,神疲乏力,舌淡苔白,脉象细弱,治方选( )丁某,男,23岁。连饮冰汽水3瓶,又食生梨后,突发胃脘剧痛,温熨脘部其痛可减,
肾盂肾炎患者尿路感染最常见的致病菌为
A.胎元饮B.寿胎丸C.圣愈汤加味D.保阴煎E.泰山磐石散治疗肾虚型胎漏、胎动不安主方是
矿山工程进度拖延时,正确的事后措施包括有()。
()是智力技能的实践模式,即把主体在头脑中应建立起来的活动程序计划,以外显的操作方式付诸执行。
下列人物中,在15世纪航行到达印度的有()。①哥伦布②郑和③迪亚士④达.伽马⑤麦哲伦
A、I’mnotwrong.B、Iagree.C、Iamright.D、I’vegotafever.D“What’swrongwithyou?”即“你怎么了?”,通常用于询问他人哪里不舒服。D选项“I’vegotafev
最新回复
(
0
)