1994 Passage 4
"Ihavegreatconfidencethatbytheendofthedecadewe'llknowinvastdetailhowcancercellsarise," saysmicrobiologistRobertWeinberg, anexpertoncancer. "But," hecautions, "somepeoplemayhavetheideathatonceoneunderstandsthecauses, thecurewillrapidlyfollow. ConsiderPasteur. Hediscoveredthecausesofmanykindsofinfections, butitwasfiftyorsixtyyearsbeforecureswereavailable."
Thisyear, 50 percentofthe 910000 peoplewhosufferfromcancerwillsurviveatleastfiveyears. Intheyear 2000, theNationalCancerInstituteestimates, thatfigurewillbe 75 percent. Forsomeskincancers, thefive-yearsurvivalrateisashighas 90 percent. Butothersurvivalstatisticsarestilldiscouraging — 13 percentforlungcancer, and 2 percentforcancerofthepancreas.
Withasmanyas 120 varietiesinexistence, discoveringhowcancerworksisnoteasy. Theresearchersmadegreatprogressintheearly 1970s, whentheydiscoveredthatoncogenes, whicharecancer-causinggenes, areinactiveinnormalcells. Anythingfromcosmicraystoradiationtodietmayactivateadormantoncogene, buthowremainsunknown. Ifseveraloncogenesaredrivenintoaction, thecell, unabletoturnthemoff, becomescancerous.
Theexactmechanismsinvolvedarestillmysterious, butthelikelihoodthatmanycancersareinitiatedatthelevelofgenessuggeststhatwewillneverpreventallcancers. "Changesareanormalpartoftheevolutionaryprocess," saysoncologistWilliamHayward. Environmentalfactorscanneverbetotallyeliminated; asHaywardpointsout, "Wecan'tprepareamedicineagainstcosmicrays."
Theprospectsforcure, thoughstilldistant, arebrighter.
"First, weneedtounderstandhowthenormalcellcontrolsitself. Second, wehavetodeterminewhethertherearealimitednumberofgenesincellswhicharealwaysresponsibleforatleastpartofthetrouble. Ifwecanunderstandhowcancerworks, wecancounteractitsaction."
63. TheexampleofPasteurinthepassageisusedto ________.
[A] predictthatthesecretofcancerwillbedisclosedinadecade
[B] indicatethattheprospectsforcuringcancerarebright
[C] provethatcancerwillbecuredinfiftytosixtyyears
[D] warnthatthereisstillalongwaytogobeforecancercanbeconquered
64. Theauthorimpliesthatbytheyear 2000, ________.
[A] therewillbeadrasticriseinthefive-yearsurvivalrateofskin-cancerpatients
[B] 90 percentoftheskin-cancerpatientstodaywillstillbeliving
[C] thesurvivalstatisticswillbefairlyevenamongpatientswithvariouscancers
[D] therewon'tbeadrasticincreaseofsurvivalrateofallcancerpatients
65. Oncogenesarecancer-causinggenes ________.
[A] thatarealwaysinoperationinahealthyperson
[B] whichremainunharmfulsolongastheyarenotactivated
[C] thatcanbedrivenoutofnormalcells
[D] whichnormalcellcan'tturnoff
66. Theword "dormant'inthethirdparagraphmostprobably
1994年硕士入学考试英语阅读真题附答案详解:TEXT4
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