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生物专业英语 Biolo gy En lish 李关荣 王贵学 西南师范大学出版社

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Page 1: 生物专业英语 - idl.hbdlib.cnidl.hbdlib.cn/book/00000000000000/pdfbook2/008/004/248763.pdf · chaelM.CoxEds,2000 ... 全书共分13个单元:科技英语的概念及写作特点,细胞

书书书

生物专业英语BiologyEnglish

李关荣 王贵学 主 编

西南师范大学出版社

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图书在版编目(CIP)数据

 生物专业英语/李关荣,王贵学主编.—重庆:西南师范大学

出版社,2007.9

ISBN9787562138785

Ⅰ.生… Ⅱ.李… Ⅲ.生物学—英语—高等学校—教材

Ⅳ.H31

中国版本图书馆CIP数据核字(2007)第076761号

生物专业英语李关荣 王贵学 主编

责任编辑:李 玲 杜珍辉

出版发行:西南师范大学出版社

地址:重庆市北碚区天生路1号

邮编:400715 市场营销部电话:023-68868624http://www.xscbs.com

经  销:全国新华书店

印  刷:西南农业大学印刷厂

开  本:787mm×1092mm 1/16印  张:10.5字  数:248千字

版  次:2007年9月 第1版

印  次:2007年9月 第1次印刷

书  号:ISBN 9787562138785

定  价:17.00元

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书书书

前 言

《生物专业英语》是全国许多高等院校生物技术、生物科

学、生物工程及相关专业的必选课之一。它是在学生具有一

定的相关生物学基础知识上,通过学习相关的反映这些普通

生物学和现代生物学的基础知识的英文短文,掌握生物学基

本知识及其英文表述方法和特点,了解现代生命科学的发展

方向和研究前沿,进而提高对英文科技文章的阅读和理解、专

业英语表达以及英文科技论文的写作能力。

本书注重现代生物学发展趋势,兼顾继承和发展,正确处

理了经典生物学和现代生物学知识及生物学问题的关系,理

论联系实际。并考虑教学特点,拓宽学生的 生 物 学 基 础 知 识

面,兼顾生物学一级学科的主要分支,重点突出,脉络清晰。

本书是作者根据多年的专业英语教学经验和积累的大量

相关资料,经系统整理、修订而完成的。为保持专业英语的地

道性和 时 代 特 点,内 容 来 源 于 如 美 国 的《时 代 周 刊》、Leh

ningerPrinciplesofBiochemistry(DavidL.NelsonandMi

chaelM.CoxEds,2000,the3rdedition)以及国内外许多相

关学 习 网 站 等 多 种 媒 体,经 系 统 整 理 改 编,主 要 用 于 教 学 目

的。编者对相关人员和单位表示衷心的感谢。主要内容有动

物、植物、微生物及人体的结构、生理、生化及遗传等方面的基

础知识;分子生物学、遗传工程、克隆技术、转基因学与食品安

全、基因组学、蛋白组学和生物信息学等现代生物学知识前沿

及动态。本书基本覆盖了生物学一级学科的主要分支,可供

生物技术、生物科学、生物工程、农学等相关专业的学生和教

师使用。

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全书共分13个单元:科技英语的概念及写作特点,细胞

结构和原生质的特性,生物化学,植物学及植物生理,遗传与

进化,人类解剖及生理,微生物,动物行为,食品、营养与健康,

分子生物学及转基因学,生物技术,基因组学和蛋白组学、生

物信息学基础。每 单 元 选 择 代 表 性 短 文1~7篇 以 上,共50

篇短文。短文中的专业词汇及疑难句子结构都编了号,便于

在随后的“Notes”部分查阅。专业词汇都给出了国际音标注

音和主要中文释义。

由于编者水平有限,现代生命科学发展迅猛,书中难免有

疏漏和不妥之处,望读者多提意见,以便再版时修订。

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书书书

目录

 

UNIT01 THECONCEPTANDCHARACTERISTICSOFSCIENTIFICENGLISH

1  Essay01 TheConceptofEnglishforScienceandTechnology3  Essay02 MustWeWrite?

7 UNIT02 FEATURESOFCELLSANDPROTOPLASM7  Essay03 AnIntroductiontoCells9  Essay04 MajorStructuralFeaturesofEukaryoticCells18

 

 Essay05 Colloids:CharacteristicComponentsofProtoplasmofAllCells

20 UNIT03 BIOCHEMISTRY20  Essay06 CellsandTissuesUsedinBiochemicalStudies22

 

 Essay07 TheαHelixIsaCommonProteinSecondaryStructure

25  Essay08 DNAIsaDoubleHelix27  Essay09 ReactionsoftheCitricAcidCycle30  Essay10 BloodSubstitute

35 UNIT04 BOTANYANDPLANTPHYSIOLOGY35  Essay11 StomatalAnatomy36  Essay12 TheParadoxofPores38  Essay13 Osmosis40  Essay14 PrinciplesofPhotosyntheticEnergyTransformation44  Essay15 DesertPlantSurvival

48 UNIT05 GENETICSANDEVOLUTION48  Essay16 Mendel'sGeneticLaws51  Essay17 WhatIsaGeneticMap?

53  Essay18 BiologicalEvolution

57 UNIT06 HUMANANATOMYANDPHYSIOLOGY57  Essay19 TheHumanBrain58  Essay20 Diagnosis:Female

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64 UNIT07 MICROBES64

 

 Essay21 AgrobacteriumtumefaciensandItsUsesinPlantBreeding

67  Essay22 BacillusthuringiensisandItsUses72  Essay23 SomeFactsAboutE.coli

75 UNIT08 ANIMALBEHAVIOR75  Essay24 TheElephant77  Essay25 LivingTogether78  Essay26 CrazyOwnersMakeforCrazyPets79  Essay27 FishandSound82  Essay28 Animals’UsesofCryingandBegging83  Essay29 FrogCalls86  Essay30 Dolphins

91 UNIT09 FOOD,NUTRITIONANDHEALTH91  Essay31 Food93  Essay32 Vitamins95  Essay33 FoodsThatFightCancer

97 UNIT10 MOLECULARBIOLOGYANDTRANSGENICS97  Essay34 ThePolymeraseChainReaction(PCR),theBasics99  Essay35 MethodsofPlantGeneTransfer100  Essay36 GenesandMoney—PaternityTest102  Essay37 GeneGunSpeedsSearchforNewOrchidColors103

 

 Essay38 PatentingGeneSequences:NotintheBestInterestsofScienceorSociety

107 UNIT11 BIOTECHNOLOGY107  Essay39 PlantTissueCulture111  Essay40 CloningTechniques113  Essay41 HowtoCloneaHerd?

114  Essay42 Clones:AsmanyTwinsAsYouLike!

115  Essay43 StemCellsandTheirUses120

 

 Essay44 WhatIfMyTesttubeBabiesWereSwappedintheLab?

122 UNIT12 GENOMICSANDPROTEOMICS122  Essay45 Genomics124  Essay46 RiceGenomeWorkCreatesHope

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126  Essay47ScientistsCrackGeneCodeofRice127  Essay48 GrainsofHope133  Essay49 Proteomics

136 UNIT13 Bioinformatics136  Essay50 Bioinformatics,theBasics

145 附录1 生物专业英语常见词素

149 附录2 生物专业英语常见词缀

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书书书

1    

犝犖犐犜01 犜犎犈犆犗犖犆犈犘犜犃犖犇犆犎犃犚犃犆犜犈犚犐犛犜犐犆犛犗犉犛犆犐犈犖犜犐犉犐犆犈犖犌犔犐犛犎

犈狊狊犪狔01 犜犺犲犆狅狀犮犲狆狋狅犳犈狀犵犾犻狊犺犳狅狉犛犮犻犲狀犮犲犪狀犱犜犲犮犺狀狅犾狅犵狔

1.Englishisagloballanguage.Withtheriseandrapidspreadingofelectroniccommunication,worldwidetradeandinternationaltravel,itsstatushasfarsurpassedthatofalinklanguage.Tosomeextent,Englishisequatedwithsuccess.Whereveryougo,fromtheluxuriantrainforestsofCostaRica[1]totheuntamedwildsofSerengeti[2]tothehodge

podge[3]ofEasternbazaars[4],you’resuretofindsomeonewhospeaksEnglishalbeit[5]

inanaccentfardifferentfromyours.Ifnothingelse,EnglishmakesadisguisedappearanceinhybridssuchasFranglais[6],Spanglish[7],Hindlish[8],Chinglish[9],etc.

2.NowadaysEnglishisestablishednotjustasthelinquafranka[10]oftheworldbutalsoastheinternationallanguageofscienceandtechnology.AnincreasingnumberofscientistsandtechniciansacrosstheworldareobligedtoreadanincreasingproportionofresearchpapersandtextbookswritteninscientificEnglish.OverthelastdecadesorsothetermEST,EnglishforScienceandTechnology,hasappearedfrequentlyinEnglishteachingrelatedliterature.

3.ThelanguageofESTthatexpressesscientificandtechnicalconcepts,theoriesandfactsisnotadifferentlanguagefromthatofthedailyconversationorliterature.But,duetoitsroleinscienceandtechnology,ESTcoversaspecialrangeofEnglish.Englishlan

guagelearnersrequireEnglishsoastopromotetheireducationalspecialtyortoperformefficientlytheirrolesasscientists,technologists,technicians,etc.AgeneralEnglishcanhardly meetsuchneedsasthese.Consequently,EnglishforSpecialPurposes(ESP)[11]hasemergedasabranchofEnglishlanguagestudy.

4.ESPconsistsofEAP[12](EnglishforAcademicPurposes),EOP[13](EnglishforOccupa

tionalorVocationalPurposes)andEST[14](EnglishforScienceandTechnology).EAPisusedbyoverseasstudents,researchersandvisitingscholarsatschoolsanduniversitiesinBritainandAmericaorinanyothercountrieswhereEnglishisusedincoursesandlectures;IntheUnitedStatesEOP(EnglishforOccupationalorVocationalPurposes)isalsocalled“EnglishforCareers”.ItistheEnglishnecessaryforsomeoccupationalrequirements,e.g.forinternationaltelephoneoperators,internationalairtrafficcontrollers,internationalcommerce,internationalrailways,computerprogramming,

tourismandsoon,orvocationaltrainingprograms,e.g.forhotelandcateringstaff,

technicaltrades,etc.

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UNIT01 犜犎犈犆犗犖犆犈犘犜犃犖犇犆犎犃犚犃犆犜犈犚犐犛犜犐犆犛犗犉犛犆犐犈犖犜犐犉犐犆犈犖犌犔犐犛犎

2    

5.Oureraistheageofmachines,electroniccomputersandeveradvancingbiology.Onlybyobtainingasolidknowledgeofscience,canonefunctionnormallyandsuccessfullyinmodernsociety.Withthedevelopmentofscienceandtechnology,especiallybiologyrelateddisciplines,scientistsandengineersstrivetoexchangetheirideas,discoveriesandinventions,collectinformationanddata,interpretconceptsandtheories,commentonthelatestscientificadvancesandwritereportsbasedonexperimentalprocedures,etc.Moreandmorescientifictermsfrommodernbiologysuchas,clone[15],GM[16](Genetically modified)foods,gene,genomics[17],proteomics[18],transgenics[19],DNAchips[20],etc.,arebecomingpopularized.Theneedincreasesdaybydayforscientistsandengineerstohaveaswift,economical,efficient,impersonalandsometimesinternationalmeansofcommunication.

6.However,ESTisnotthepopularizedaccountsofthetechnicalsubjectsasarefoundinencyclopedias[21]orbooksintendedforgeneralreaders.Ithasitsownauthentic[22]languageofscience!Lately,textbookshavebeenappearingthatattempttoreflectthenatureofthelanguageactuallyusedbyscientistsandthefunctionitserves.HoweversomepeoplestillignoretheexistenceofESTalltogether,whileothersarequiteindifferenttoit.Theydrawasimpleformulalikethis:EST=GeneralEnglishGrammar+TechnicalWords.TheythoughtthattheywouldbeabletounderstandESTbysimplyknowinggrammaticalrulesinadditiontosometechnicalwords.

7.Unfortunately,thisjudgmentgivesnofruitfulcomprehensionaboutthenatureofEST.TheydonotseemtobeawarethatESTpresentslinguisticvarietieswithitsowncharacteristicfeatures.

8.Sincescientiststrytobeimpersonalinnarratingthenaturalphenomenaandfacts,theirprocesses,propertiesandcharacteristics,EnglishforScienceandTechnology(EST)

mustbeevidentlyprecise,concise,clearandrestrictedandincludesmanymathematicalequations,formulae,diagrams,tables,etc.Biologyrelatedpublicationsaremoresoever.Scientistsalsoprefersometypicalsentencepatternsandalargenumberoftechnicalandsemitechnicalterms,whichmakeEnglishforScienceandTechnologydifferenttoaverywideextentfromordinaryEnglish.

 Notes

[1]CostaRica[5kRstE5ri:kE]n.哥斯达

黎加

[2]Serengeti[siren`giti]n.塞伦盖提

[3]hodgepodge[5hRdVpCdV]n.大杂烩

[4]bazaar[bE5zB:]n.集市,闹市

[5]albeit[C:l5bi:it]adv.虽然

[6]Franglais[frB:n5glei]n.(法语中的)

英语外来语

[7]Spanglish[5spAnliF]n.混有 西 班 牙

文英语

[8]Hindlish[hindliF]n.混有印度语的英语

[9]Chinglish[tFin^liF]n.混有 中 文 的 英

[10]linquafranka[5liN^ w[5frANk[]n.

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3    

通用语,混合语

[11]ESP:EnglishforSpecialPurposes特

殊用途英语

[12]EAP:EnglishforAcademic[7AkE5demik]Purposes学术用途英语

[13] EOP: English for Occupational[7Rkju5peiF[n[l]orVocational[vEu5keiF[n[l]Purposes职业英语

[14]EST:EnglishforScienceandTechnology科技英语

[15]clone[kl[un]n.克隆

[16]GM (Geneticallymodified)food遗传

修饰食品

[17]genomics[`dVi:n[Umiks]n.基 因 组

[18]proteomics[`pr[uti[umiks]n.蛋白组

[19]transgenics[trAns5dVeniks]n.转基

因学

[20]DNAchip[tFip]DNA芯片

[21]encyclopedia[en7sBikl[u5pi:di[]n.百科全书

[22]authentic[R:5Wentik]adj.真 实 可

信的

犈狊狊犪狔02 犕狌狊狋犠犲犠狉犻狋犲?

1.Manynewfindingsanddiscoveriesaredocumentedwithreferencestothescientificliterature,indicatedbythenamesoftheauthor(s)andtheyearofpublication.Publication,

asitturnsout,isanabsolutelyessentialpartofthescientificprogress,asPageMorganexplainsinthisessay.Dr.MorganisaProfessorofPlantPhysiologyintheDepartmentofSoilandCropScienceatTexasA&MUniversity.Formanyyears,hehasalsobeenanAssociateEditor(forplantdevelopmentandgrowthregulators)ofthejournalPlantPhysiology.Prof.Morgantellsushowthesystemworksandgivesafewpointerstomanuscriptpreparationforthescientificliterature.

2.Scientistsmustwrite!Knowledgeuncommunicatediseffectivelyunknown;discoveryisbutonesteponthepathofunderstanding.Althoughyoumayagreewiththesestatements,youmaynotbeawarehowoftenscientistsandsciencestudents[1]arepoorly

preparedtowrite.Aregenesforwriters’block[2]linkedtothoseforinvestigativetalent?Probablynot,butwhileastudentisstudyingtheconceptsofscience,practicingitstechniques,andlearningitsliterature,itmaybedifficulttofindthetimetodevelopgoodcommunicationsskills.Theseskillstakepracticetodevelop.Educatorssoonlearnthatmanystudentshatetowrite.Givenmyexperienceinteaching,advisinggraduatestudents,andservingasadecisioneditor[3]forascientificjournal,Iwouldliketodiscusswritingwiththereadersofthistext.

3.Thefirstpointisthatwritingisnecessary.Asayoungfaculty[4]memberIremember

hearingourDean[5]say,“Researchisnotcompleteduntilitispublished.”Hewasright.Studentsmustultimatelywritewhattheyhavediscoveredorlearned.Quizzes,

reports,termpapers,theses,anddissertations[6]allowotherstoknowandjudgeyour

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UNIT01 犜犎犈犆犗犖犆犈犘犜犃犖犇犆犎犃犚犃犆犜犈犚犐犛犜犐犆犛犗犉犛犆犐犈犖犜犐犉犐犆犈犖犌犔犐犛犎

4    

abilityandaccomplishments.Studentswhofollowascientificcareersoonareinvolvedinwrittencommunications:justifications[7]forequipmentpurchases,courseoutlines,

researchfundingproposals,andmanuscriptsreportingresearchfindings.Reviewarticles[8],booksandpiecesforthesemipopular[9]press,flowfromthepens(orcomputerkeyboards)ofthemoreprolific[10].Writingisessentialinscience!

4.Thisdiscussionisnottoadvocates“PublishorPerish[11]”,butrather“PublishorNoOneWillKnow.”Untilyoumentallywrestlewith[12]aquestionandwritedownyourbestanswer,yourinstructorcannotevaluatehowwellyouhavelearned.Likewise,untilscientistshavepublishedtheresultsandconclusionsfromtheirexperiments,nooneelsecanevaluate[13]thesignificanceandusefulnessofthework.Onlyafternewfactsandideasarepublished,discussed,andreplicated[14]byfurthertestingcanthevalidonesultimatelycontributetoadvancingunderstandinginscienceasawhole.

5.Unfortunately,it’snotenoughtowrite;theneedistowritewell.Considertwostudentswhospendhoursinthelibraryresearchingthesametermpapertopic.Equallywellversed[15]inthefacts,onewritesanuninspired[16],cataloglikelistingofwhodidwhatandwhen.Thesecondstudentidentifiestherelevantquestions,arraysthefactstosupportlogicaldeductions[17],andbringsthetopictoasharplyfocusedconclusion.Onewroteandtheotherwrotewell.Attheprofessionalleveltheobjectiveforwritingascientificpaperisnottogetitpublished,butrathertocommunicatewithotherscientists.Everyonehasalimitedamountoftime.Writersareliterally[18]competingforthetimeandattentionofpotentialreaders.Regardlessofhowimportantadiscoveryis,itwillusuallybemorerapidlyacceptedifitispresentedinawellwrittenpaper.Ontheotherhand,ifthewritingispoorandthemessageobscure,readerswilloftenquitbeforecompletingthepaper.

6.Perhapssome“do’s”and“don’ts”wouldbehelpful.Mostinstructorshaveseenalotofbadwriting;thus,the“don’ts”areeasytolist.Inmyexperience,themostcommonerroristhatwritersfailtoclearlystatetheirmessage.Thereaderwonders:whatdowelearnaboutplantphysiologyfromtheexperiment?Isitneworunique?Isituseful?Thestudentwritingalabreport[19]orthescientistwritingforajournalhastheresponsibilitytoanswerthosequestions.Anothercommonerroroccurswhenamanuscriptappearstobeapartiallycondensedthesis.Themessageislostinwordiness[20]andsecondarytopics,anda10pagestorygetstoldin25.Also,thetechnicallanguageofexperimentaldesignandstatisticsisoftenusedasawritingcrutch[21];Asaresult,clarity[22]suffers.Readersareusuallyinterestedinwhattheresponsewas,anditsmagnitude,variability,

andreproducibility.Jargon[23]about“significantthreewayinteractionsincompletefactorials”promptsdrowsiness.

7.Anothercommonwritingerroriscarelesspreparation.Mostwritingtasks,whethersomethingassimpleasanessayexaminationorascomplicatedasreviewedjournalmanuscript,includinginstructions.Yettimeaftertimewritersappeartoignoretheinstructionsandsubmitcarelesslypreparedmaterial.Theaxiom[24]“Younevergetasecond

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chancetomakeagoodfirstimpression”certainlyappliestowriting.Althoughtechnicalaspectsofcompositionarebeyondthescopeofthisessay,studentswouldbewellservedtodevelopthehabitofreviewingtheirwritingforspelling,punctuation,andsentencestructurebeforeitissubmittedtoothers.Writinghandbookslistthecommonmistakes,suchasusingwhichinplaceofthat.Equipyourselfwithagoodwritinghandbookandadictionary,andusethem!

8.Thepositivesuggestionsforscientificwritingmuststartwiththescientificmethod.Thereisnosubstituteforexpressingthetopicasaquestionthatcanbeanswered.Searchingoutwhatisalreadyknownisequallyindispensable[25].Ifawritersitsdowntowrite,forexample,aboutsometopicasbroadas“tissueculturestudieswithsoybeans,”orifawriterdismissesrelevantbackgroundknowledgewithwordssuchas“littleisknownaboutthissubject”,thepapermayalreadybeunsalvageable.Writersshouldhavetheprimarymessageoftheirpapersinmindbeforetheywritethefirstword.Thatmessage,infact,shouldbeananswertoaclearlystatedquestion,anditshouldshapethetitle,theintroduction,andthebodyofthepaper.Inthatwayreaderscanrecognizeatheme[26]thatisconsistentthroughoutthepaper.

9.Thepurposeofscientificwritingistocommunicatefindings,analyses,conclusions,andtheories.Communicateistheoperative[27]word.Unlessthereaderunderstands,thewriterhasfailed.Theimplications[28]areobvious:Identifytheaudienceandwritetothatlevelofunderstanding.Clarityisofteninverselyrelatedtosentencelength.Abarrage[29]ofwordswithobscuremeaningsmakesreadingachore[30]ratherthanapleasure.Thewordsselectedshouldaidcommunicationratherthanmakeastatementaboutthewriter’svocabulary.Sentencesthatcanbemisunderstoodusuallywillbe.Brevity[31]isavirtuewhenwedtoclarity.Writersshouldwriteinadirect,simple,logicalstyle;therewardisbeingreadandbeingunderstood.

10.Writersshouldgiveseriousattentiontographicillustration.Pooronesfrequentlyappeartobeanafterthought[32].Excellentillustrationsoffindingsorconclusionsareoftenthemosteffectivewaytocommunicate.Thesayingthat“Onepictureisworthathousandwords”makesthatpoint.Goodillustrationsdon’tjusthappen;theytaketheforethought[33],inventivenessandwork.Wetraingraduatestudentstogiveseminarswithmuchemphasisongoodslides.Thatemphasisisintendedtocarryoverintotheirwrittencommunications.Computergraphicsmakethejobeasier,butthebottomlineisstillpersonalinitiative[34].

11.Inconclusion,theabilitytowritewellisaskillneededbysciencestudentsandscientistsalike.Itcanbeacquiredandcultivatedifthebasicgoalofcommunicationiskeptclearlyinview.Thosewhocanthinkandspeaklogicallycanlearntowritelogically,andeveninterestinglyandentertainingly.Sciencewillbethebetterforsuchwriting!

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UNIT01 犜犎犈犆犗犖犆犈犘犜犃犖犇犆犎犃犚犃犆犜犈犚犐犛犜犐犆犛犗犉犛犆犐犈犖犜犐犉犐犆犈犖犌犔犐犛犎

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 Notes

[1]sciencestudentn.理科学生

[2]blockn.(俚语)脑袋

[3]decisioneditor[di5siV[n5edit[]决策

编辑

[4]faculty[5fAk[lti]n.全体教员

[5]Dean[di:n]n.大学院长,系主任

[6]dissertation[9dis[5teiF[n]n.(学位)论文,专题,论述,学术演讲

[7]justification[dVQstifi5keiF[n]n.认

为有理,认为正当,理由,辩护,释罪

[8]reviewarticlen.综述文章

[9]semipopularadj.半科普的

[10]prolific[pr[5lifik]adj.多产的,丰富

的,大量繁殖的

[11]perish[`periF]vi.毁灭,死亡,腐烂,枯萎vt.毁坏,使麻木

[12]wrestle[5resl]withvi.与……搏斗

[13]evaluate[i5vAljueit]vt.评 价,估 计,求……的值v.评价

[14]replicate[`replikit]v.复制

[15]versed[v[:st]adj.熟练的,精通的

[16]uninspired [`Qnin5spai[d]adj.未 赋

予灵感的,缺乏创见的,平凡的

[17]deduction[di`dQkF[n]n.缩 小,减

小,扣除,折扣,扣 除 额,折 扣 额,推

论,演绎法

[18]literally[`lit[r[li]adv.照 字 面 意 义,

逐字地

[19]labreport实验报告

[20]wordiness[`w[:dines]n.多嘴,冗长

[21]crutch[krQtF]n.(跛 子 用 的)拐 杖,支撑,帮助

[22]clarity[5lAriti]n.清楚,透明

[23]jargon[`dVB:g[n]n.行话

[24]axiom [`Aksi[m]n.公 理,自 明 之 理:不言而喻的或普遍被认定的真理;格言

[25]indispensable[9indis5pens[bl]adj.不可缺少的,绝对必要的

[26]theme[Wi:m]n.(谈 话,写 作 等 的)题目,主题

[27]operative[`Rp[r[tiv]adj.有效的;有

力量的;行动的,实用的

[28]implication[9impli`keiFEn]n.牵 连,纠缠,含蓄,含意,暗示

[29]barrage[`bArB:V]n.拦河坝,堰,阻

塞,(敌军前进的)弹幕射击

[30]chore[tFR:]n.家务琐事

[31]brevity[5breviti]n.(时间)短暂,(讲话,文章等)简短

[32]afterthought[`B:ft[WR:t]n.事后产

生的想法,追悔,再思

[33]forethought[`fR:WC:t]n.深谋远虑,先见

[34]initiative[i`niF[tiv]n.主动性

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犝犖犐犜02 犉犈犃犜犝犚犈犛犗犉犆犈犔犔犛犃犖犇犘犚犗犜犗犘犔犃犛犕

犈狊狊犪狔03 犃狀犐狀狋狉狅犱狌犮狋犻狅狀狋狅犆犲犾犾狊

1.Cellsarethestructuralandfunctionalunitsofalllivingorganisms.Thesmallestorganismsconsistofsinglecellsandaremicroscopic,whereaslargerorganismsaremulticellular[1].Thehumanbody,forexample,containsatleast1014cells.Unicellular[2]or

ganismsarefoundingreatvarietiesthroughoutvirtuallyeveryenvironmentfromAntarcticatohotspringstotheinnerrecesses[3]oflargerorganisms.Multicellularorganismscontainmanydifferenttypesofcells,whichvaryinsize,shape,andspecializedfunction.Yetnomatterhowlargeandcomplextheorganism,eachofitscellsretainssomeindividualityandindependence.

2.Despitetheirmanydifferences,cellsofallkindssharecertainstructuralfeatures.The

plasmamembrane[4]definestheperiphery[5]ofthecell,separatingitscontentsfromthesurroundings.Itiscomposedofenormousnumbersoflipidandproteinmolecules,heldtogetherprimarilybynoncovalenthydrophobicinteractions[6],formingathin,tough,

pliable,hydrophobiclayeraroundthecell.Themembraneisabarriertothefreepassageofinorganicionsandmostotherchargedorpolarcompounds.Transportproteins[7]intheplasmamembraneallowthepassageofcertainionsandmolecules.Othermembraneproteinsincludereceptors[8]thattransmitsignalsfromtheoutsidetotheinsideofthecellandenzymes[9]thatparticipateinmembraneassociatedreactionpathways.

3.Becausetheindividuallipidsandproteinsoftheplasmamembranearenotcovalentlylinked,theentirestructureisremarkablyflexible,allowingchangesintheshapeandsizeofthecell.Asacellgrows,newlymadelipidandproteinmoleculesareinsertedintoitsplasmamembrane;celldivision[10]producestwocells,eachwithitsownmembrane.Growthandfissionoccurwithoutlossofmembraneintegrity[11].Inareversalofthefissionprocess,twoseparatemembranesurfacescanfuse,alsowithoutlossofintegrity.Membranefusionandfissionarecentraltomechanismsoftransportintoandoutofthecellsknownasendocytosis[12]andexocytosis[13],respectively.

4.Theinternalvolumeboundedbytheplasmamembrane,thecytoplasm[14],iscomposedofanaqueoussolution,thecytosol[15],andavarietyofinsoluble,suspendedparticles.Thecytosolisahighlyconcentratedaqueoussolutionwithacomplexcompositionand

gellikeconsistency.DissolvedinthecytosolaremanyenzymesandtheRNAmolecules

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thatencode[16]them,themonomericsubunits[17](aminoacids[18]andnucleotides[19])

fromwhichthesemacromolecules[20]areassembled,hundredsofsmallorganicmoleculescalledmetabolites[21],intermediatesinbiosyntheticanddegradativepathways,enzymes[22]thatareessentialparticipantsinmanyenzymecatalyzedreactions,andinorganicions.

5.Amongtheparticlessuspendedinthecytosolaresupramolecularcomplexes[23]and,inalmostallnonbacterialcells,avarietyofmembraneboundedorganelles[24]containingspecializedmetabolicmachinery.Ribosomes[25],smallparticles18to22nmindiameter,thatarecomposedofover50differentproteinandRNAmolecules,arethesitesatwhichproteinsynthesisoccurs.Ribosomesengagedinproteinsynthesisoftenoccurinclusterscalledpolysomes(polyribosomes)[26]heldtogetherbyastrandofmessengerRNA.Alsopresentinthecytoplasmofmanycellsaregranulesordropletscontainingstorednutrientssuchasstarchandfat.

6.Alllivingcellshave,foratleastsomepartoftheirlife,eitheranucleus[27]oranucleoid[28],inwhichthegenome[29](thecompletesetofgenescomposedofDNA)isstoredandreplicated.TheDNAmoleculesarealwaysfarlongerthanthecellsthemselvesandaretightlyfoldedandpackedwithinthenucleusornucleoidassupramolecularcomplexesofDNAwithspecificproteins.Thebacterialnucleiodisnotseparatedfromthecytoplasmbyamembrane,butinhigherorganismsthenuclearmaterialisenclosedwithinadoublemembrane,thenuclearenvelope[30].Cellswithnuclearenvelopesarecalledeukaryotes[31](Greekeu,“true”,andKaryon,nucleus);thosewithoutnuclearenvelopsbacterialcellsareprokaryotes[32](Greekpro,‘before’).

7.Unlikebacteria,eukaryoteshaveavarietyofothermembraneboundedorganellesintheircytoplasm,includingmitochondria[33],endoplasmicreticulum[34],Golgicomplexes[35],lysosomes[36]andvacuoles[37](relatedorganellesfoundinanimalandplantcells,

respectively),and,inphotosyntheticcells,chloroplasts[38].

 Notes

[1]multicellular[7mQlti`seljul[]adj.多

细胞的

[2]unicellular[`ju:ni`seljul[]adj.单细胞

[3]recess[ri`ses]n.(墙壁等的)凹进处,[解]隐窝

[4]plasmamembrane [`plAzm[` membrein]n.质膜

[5]periphery[p[`rif[ri]n.外围

[6]noncovalenthydrophobicinteraction

[7nQnkEU`veil[nt7hBidr[J`f[Jbik9int[r`AkF[n]非共价键疏水相互作用

[7]transportproteinn.转运蛋白

[8]receptorsn.受体

[9]enzyme[`enzaim]n.酶

[10]celldivisionn.细胞分裂

[11]membraneintegrity[`membreinin`tegriti]n.膜的完整性

[12]endocytosis[9end[usBi`t[usis]n.(细

胞)内吞作用

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[13]exocytosis[9eks[usai`t[usis]n.胞外

分泌

[14]cytoplasm [`sait[uplAzm]n.(细)胞质

[15]cytosol[`sait[usCl]n.(细)胞浆

[16]encode[in5k[ud]vt.编码

[17]monomericsubunit [7mRn[`meriksQb5jU:nit]n.单体亚单位

[18]aminoacid[5Amin[U` Asid]氨基酸

[19]nucleotide[`njU:kli[taid]n.核苷酸

[20]macromolecule[9mAkr[U`mRlikju:l]

n.大分子,高分子

[21]metabolite[mi`tAb[lait]n.代谢物

[22]coenzyme[k[U`enzaim]]n.辅酶

[23]supramolecularcomplex[9sjU:pr[m[`

lekjul[`kRmpleks]超分子复合物

[24]organelle[9C:g[`nel]n.细胞器

[25]ribosome[`raib[s[um]n.核糖体

[26]polysome[`pRlis[um](polyribosome)[9pRli`raib[s[um]n.多核糖体

[27]nucleus[`njU:kli[s]n.细胞核,核[28]nucleoid[`njU:kliRid]n.类核

[29]genome[`dVi:n[Um]n.基因组

[30]nuclearenvelope[`njU:kli[`envil[Up]

n.核膜

[31]eukaryote[ju`kAri[ut]n.真核细胞

[32]prokaryote[pr[U`kAri[ut]n.原核细

[33]mitochondrion[9mait[`kRndri[n]n.线 粒 体(sing.)mitochondria[9mait[`

kRndri[]线粒体(pl)[34]endoplasmicreticulum [`end[u9plAzmik

ri`tikjul[m]n.内质网

[35]Golgicomplex [`gC:ldVi`kRmpleks]

n.高尔基复合体

[36]lysosome[`lais[s[Um]n.溶酶体

[37]vacuole[`vAkju[ul]n.液泡

[38]chloroplast[`klCr[plB:st]n.叶绿体

犈狊狊犪狔04 犕犪犼狅狉犛狋狉狌犮狋狌狉犪犾犉犲犪狋狌狉犲狊狅犳犈狌犽犪狉狔狅狋犻犮犆犲犾犾狊

1.Typicaleukaryoticcellsaremuchlargerthanprokaryoticcells—commonly5to100μmindiameter,withcellvolumesathousandtoamilliontimeslargerthanthoseofbacteria.Thedistinguishingcharacteristicofeukaryotesisthenucleus,whichhasacomplexinternalstructuresurroundedbyadoublemembrane.Anotherstrikingdifferencebetweeneukaryotesandprokaryotesisthateukaryotescontainanumberofothermembraneboundedorganelles.Thefollowingdescribethestructuresandrolesofthecom

ponentsofeukaryoticcellsinmoredetail.

ThePlasmaMembraneContainsTransportersandReceptors2.Theexternalsurfaceofacellisincontactwithothercells,theextracellular[1]fluid,andthesolutes,nutrientmolecules,hormones[2],neurotransmitters[3],andantigens[4]inthatfluid.Theplasmamembranesofallcellscontainmanytransporters,proteinsthatspanthemembraneandcarrynutrientsintothecellandvariousproductsout.Cellsalsohavesurfacemembraneproteins(signalreceptors[5])withhighlyspecificbindingsitesforextracellularsignalingmolecules(receptorligands[6]).Whenanexternalligandbindstoitsspecificreceptor,thereceptorproteintransducesthesignalcarriedbythat

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ligandintoanintracellular[7]message.Forexample,somesurfacereceptorsareassociatedwithionchannels[8]thatopenwhenthereceptorisoccupied,permittingentryofspecificions;othersactivateorinhibitcellularenzymesontheinnermembranesurface.Whateverthemodeofsignaltransduction,surfacereceptorscharacteristicallyactassignalamplifiers-asingleligandmoleculeboundtoasinglereceptormaycausethefluxofthousandsofionsthruanopenedchannelorthesynthesisofthousandsofmoleculesofanintracellularmessengermoleculebyanactivatedenzyme.

3.Somesurfacereceptorsrecognizeligandsoflowmolecularweight,andothersrecognizemacromolecules.ForExample,bindingofacetylcholine[9](Mr=146)toitsreceptorbe

ginsacascade[10]ofcellulareventsthatunderliethetransmissionofsignalsformusclecontraction.Bloodproteins(Mr>20,000)thatcarrylipids(lipoproteins[11])arerecognizesbyspecificcellsurfacereceptors,whichmediatelipidentryintothecells.Antigens(proteins,viruses,orbacteria,recognizedbytheimmunesystemasforeign)bindtospecificreceptorsandtriggertheproductionofantibodies[12].Duringthedevelopmentofmulticellularorganisms,neighboringcellsinfluenceeachother’sdevelopmentalpaths,assignalmoleculesfromonecelltypereactwithreceptorsofothercells.Thusthesurfacemembraneofacellisacomplexmosaic[13]ofdifferentkindsofhighlyspecific“molecularantennae”[14]thruwhichcellsreceive,amplify,andreacttoexternalsignals.

4.Mostcellsofhigherplantshaveacellwalloutsidetheplasmamembrane,whichserveasarigid,protectiveshell.Thecellwall,composedofcellulose[15]andothercarbohydratepolymers,isthickbutporous.Itallowswaterandsmallmoleculestopassreadily,butswellingofthecellduetotheaccumulationofwaterisresistedbytherigidityofthewall.

EndocytosisandExocytosisCarryTrafficacrossthePlasmaMembrane5.Endocytosisisamechanismfortransportingcomponentsofthesurroundingmediumdeepintothecytoplasm.Inthisprocess,aregionoftheplasmamembraneinvaginates[16],enclosingasmallvolumeofextracellularfluidwithinabudthatpinchesoffinsidethecellbymembranefission.Theresultingsmallvesicle[17](endosome[18])canmoveintointeriorofthecell,deliveringitscontentstoanotherorganelleboundedbyasinglemembrane(alysosome,forexample)byfusionofthemembranes.Theendosomethusservesasanintracellularextensionoftheplasmamembrane,effectivelyallowingintimatecontactbetweencomponentsoftheextracellularmediumandregionsdeepwithinthecytoplasm,whichcouldnotbereachedbydiffusionalone.Phagocytosis[19]isaspecialcaseofendocytosisinwhichthematerialcarriedintothecell(withinaphagosome[20])isparticulate[21],suchasacellfragmentorevenanother,smallercell.Theinverseofendocytosisisexocytosis,inwhichavesicleinthecytoplasmmovestotheinsidesurfaceoftheplasmamembrane.Manyproteinsdestinedforsecretionintotheextracellularspacearepackagedintovesiclescalledsecretorygranulesthenreleasedbyex

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ocytosis.

TheEndoplasmicReticulumOrganizestheSynthesisofProteinsandLipids6.Thesmalltransportvesiclesmovingtoandfromontheplasmamembraneinexocytosisandendocytosisarepartsofadynamicsystemofintracellularmembranesthatincludestheendoplasmicreticulum,theGolgicomplex,thenuclearenvelope,andavarietyofsmallvesiclesaslysosomesandperoxisomes[22].Althoughgenerallyrepresentedasdiscreteandstaticelements,thesestructuresareinfactinconstantflux,withmembranevesiclescontinuallybuddingoff,movingthrough,andmergingwithmembranousstructureselsewhere.

7.Theendoplasmicreticulum(ER)isahighlyconvoluted[23],threedimensionalnetworkofmembraneenclosedspacesextendingthroughoutthecytoplasmandenclosingasubcellularcompartment[24](thelumen[25]oftheER)separatefromthecytoplasm.Themanyflattenedbranches(cisternae[26])ofthiscompartmentarecontinuouswitheachotherandwiththenuclearenvelope.Incellsspecializedforthesecretionofproteins,

suchasthepancreatic[27]cellsthatsecretethehormoneinsulin[28],theERisparticularlyprominent.Theribosomesthatsynthesizeproteinsdestinedforexportattachtotheouter(cytoplasmic)surfaceoftheER,andthesecretoryproteinsarepassedthroughthemembraneintothelumenastheyaresynthesized.DigestiveenzymesthatwillbesequesteredwithinlysosomesorproteinsdestinedforinsertionintothenuclearorplasmamembranesarealsosynthesizedonribosmesattachedtotheER.Bycontrast,proteinsthatwillremainandfunctionwithinthecytosolaresynthesizedoncytoplasmicribosomesunassociatedwiththeER.

8.Theattachmentofthousandsofribosomes(usuallyinregionsoflargecisternae)givestheroughendoplasmicreticulum(ER)[29]itsgranularappearanceandthusitsname.Inotherregionsofthecell,theERisfreeofribosomes.Thissmoothendoplasmicreticulum[30],whichisphysicallycontinuouswiththeroughER,isthesiteoflipidbiosynthesisandavarietyofotherimportantprocesses,includingthemetabolismofcertaindrugsandtoxiccompounds.SmoothERisgenerallytubular[31],incontrasttothelong,

flattenedcisternaetypicalofroughER.Insometissues(skeletalmuscle[32],forexample),theERisspecializedforthestorageandrapidreleaseofcalciumions.ReleaseofCa2+isthetriggerformanycellularevents,includingmusclecontraction.

TheGolgiComplexProcessesandSorts[33]Proteins9.NearlyalleukaryoticcellshaveGolgicomplexes,systemsofmembranoussacs,orcisternae,arrangedasflattenedstacks.Namedafteritsdiscoverer,CamilloGolgi,theGolgicomplexisasymmetric[34],structurallyandfunctionally.Thecisside[35]facestheroughER(andthenucleus),andthetransside[36]facestheplasmamembrane;betweenthesearethemedialelements.Proteins,duringtheirsynthesisonribosomesboundtotheroughER,areinsertedintotheinterior(lumen)oftheERcisternae.Smallmem

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branevesiclescontainingthenewlysynthesizedproteinsbud[37]fromtheERandmovetotheGolgicomplex,fusingwiththecisside.AstheproteinspassthrutheGolgicomplextothetransside,enzymesinthecomplexmodifytheproteinmoleculesbyaddingsulfate,carbohydrate,orlipidmoieties[38]tothesidechainsofcertainaminoacids.Oneofthefunctionsofthemodificationofanewlysynthesizedproteinisto“address”ittoitsproperdestinationasitleavestheGolgicomplexinatransportvesiclebuddingfromthetransside.Certainproteinsareenclosedinsecretorygranules[39],eventuallytobereleasedfromthecellbyexocytosis.Othersaretargetedforintracellularorganellessuchaslysosomesorforincorporationintotheplasmamembraneduringcellgrowth.

LysosomesAretheSitesofDegradativeReactions10.Lysosomes[40],foundonlyinanimalcells,aresphericalvesiclesboundedbyasingle

membranebilayer.Theyareusuallyabout1μmindiameter.Lysosomescontainenzymescapableofdigestingproteins,polysaccharides[41],nucleicacids[42],andlipids.Theyfunctionascellularrecyclingcenters[43],breakingdowncomplex moleculesbroughtintothecellbyendocytosis,fragmentsofforeigncellsbroughtinbyphagocytosis,orwornoutorganellesfromthecell’sowncytoplasm.Thesematerialsselectivelyenterthelysosomebyfusionofthelysosomalmembranewithendosomes,phagosomes,ordefectiveorganelles,andarethendegradedtotheirsimplecomponents(aminoacids,monosaccharides[44],fattyacids,etc.),whicharereleasedintothecytosoltoberecycledintonewcellularcomponentsorfurthercatabolized[45].

11.Thedegradativeenzymeswithinalysosomewouldbefreetoactonallcellularcomponentsweretheynotconfinedbythelysosomalmembrane.AsecondlineofdefenseagainstunwanteddestructionofcytosolicmacromoleculesbylysosomalenzymesisthedifferenceinpHbetweenthelysosomeandthecytosol,maintainedbytheactionofanATPfueledprotonpump[46]inthelysosomalmembrane.Thelysosomalcompartmentismoreacidic(pH5)thanthecytosol(pH≈7),andlysosomalenzymesaremuchlessactiveatthehigherpHofthecytosol.

VacuoleofPlantCellsPlaySeveralImportantRoles12.Plantcellsdonothavelysosomes,buttheirvacuolescarryoutsimilardegradativereactionsaswellasotherfunctionsfoundinanimalcells.Growingplantcellscontainseveralsmallvacuoles,vesiclesboundedbyasinglemembranebilayer.Asthecellmatures,

thevacuolesfuseandbecomeonelargecentralvacuole[47].Thevacuolemayrepresentasmuchas90%ofthetotalcellvolumeinamaturecell,pressingthecytoplasmintoathinlayerbetweenthevacuoleandtheplasmamembrane.Themembranesurroundingthevacuole,calledthetonoplast[48],regulatestheentryofions,metabolites,andcellularstructuresdestinedfordegradation,andtheliquidwithinthevacuolecontainsdigestiveenzymesthatdegradeandrecyclemacromolecularcomponents.Asinthelysosome,thepHwithinthevacuoleisgenerallylowerthanthepHofthesurroundingcytosol.In

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someplantcells,thevacuolecontainshighconcentrationsofpigments (anthocyanins[49])thatgivesflowersandfruitstheirdeeppurpleandredcolors.Inadditiontoitsroleinstorageanddegradationofcellularcomponents,thevacuolealsoprovidesphysicalsupporttotheplantcell.Becausetheconcentrationofsolutes(salts,ions,degradationproducts)isgreaterinthevacuolethaninthecytosol,waterpassesosmotically[50]

intothevacuole,establishing,atequilibrium,anoutwardturgorpressure[51]onthecytoplasmandthecellwallthatstiffenstheplanttissue.

PeroxisomesDestroyHydrogenPeroxide[52]andGlyoxysomes[53]ConvertFatstoCarbohydrates13.Someoftheoxidativereactionsinthebreakdownofaminoacidsandfatsproducefree

radicals[54]andhydrogenperoxide(H2O2),veryactivechemicalspeciesthatcoulddamagecellularmachinery.Toprotectthecellfromthesedestructivebyproducts,suchreactionsaresegregatedwithinsmallmembraneboundedvesiclescalledperoxisome.Thehydrogenperoxideisdegradedbycatalase[55],anenzymepresentathighconcentrationinperoxisomes;itcatalyzesthereaction:

2H2O →2 2H2O+ O2Glyoxysomesarespecializedperoxisomesfoundincertainplantcells.Theycontainhighconcentrationsoftheenzymesoftheglyoxylatecycle[56],ametabolicpathwayuniquetoplantsthatconvertsstoredfatstocarbohydratesduringseedgermination.Lysosomes,

peroxisomes,andglyoxysomesaresometimesreferredtocollectivelyasmicrobodies[57].

TheNucleusContainstheGenome14.Theeukaryoticnucleusisquitecomplexinstructureandbiologicalactivitycompared

withtherelativelysimplenucleoidofprokaryotes.Thenucleuscontainsallacell’sDNA,whichcanbethousandsoftimesmorethanispresentinabacterialcell;asmallamountofDNAisalsopresentinmitochondriaandchloroplasts.Thenucleusissurroundedbyanuclearenvelope,composedoftwomembranebilayersseparatedbyanarrowspaceandcontinuouswiththeroughER.Atintervalstheinnerandouternuclearmembranesarepinchedtogetheraroundopenings(nuclearpores),whichhaveadiameterofabout90nm.Associatedwiththeporesareproteinstructurescallednuclearporecomplexes,specifictransportersthatallowcertainmacromoleculestopassbetweenthecytoplasmandtheaqueousphaseofthenucleus(thenucleoplasm[58]).Trafficintothenucleusthroughthenuclearporecomplexes[59]includesenzymesandotherproteinssynthesizedinthecytoplasmandrequiredinthenucleoplasmforDNAreplicationandrepair,transcription,andRNAprocessing.PassingoutthroughthenuclearporesaremessengerRNAprecursors,withassociatedproteins,whichwillbetranslatedonribosomesinthecytoplasm.

15.Thenucleusofaninterphase(nondividing)cellisfilledwithadiffusematerial[60]calledchromatin[61],socalledbecauseitstainedbrightlywithcertaindyes.Chromatinconsists

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ofDNAandproteinsboundtightlytogetherandisthesubstanceofthechromosomes,

whichdonotcondenseandbecomeindividuallyvisibleuntilthecellisreadytodivide.Thenucleolus[62]isaspecificregionofthenucleusinwhichtheDNAcontainsmanycopiesofthegenesencodingribosomalRNA.Toproducethelargenumberofribosomesneededbythecell,thesegenesarecontinuouslytranscribedintoRNA.ThenucleolusappearsdenseinelectronmicrographsbecauseofitshighRNAcontent.RibosomalRNAproducedinthenucleolusentersthecytoplasmthroughthenuclearpores.

16.Nucleardivision(mitosis[63])occursbeforecelldivision(cytokinesis[64]).ThedoublehelicalDNAofthechromatinisreplicated,theninthefirstphaseofmitosisthechromatinfiberscondenseintodiscretebodies,thechromosomes[65],eachconsistingoftwoidenticalchromatids[66].Thetwosisterchromatidsseparate,onemovingtoeachpoleofthecell,wheretheybecomepartofthenewlyformednucleusofeachdaughtercell.

17.Cellsofeachspecieshaveacharacteristicnumberofchromosomesofspecificsizesandshapes.Forexample,theprotist[67]Tetrahymenapyriformis[68]has5pairs;cabbagehas9,humanshave23,andthefernOphioglossumreticulatum[69]hasabout630!Thecellsthatmakeupmostofthebodyofamulticellularorganism,thesomaticcells,havetwocopiesofeachchromosomeandaresaidtobediploid[70](2n).Gametes[71](eggsandsperm,forexample),producedbymeiosis[72]andhavingonlyonecopyofeachchromosome,arehaploid(n).Duringsexualreproduction[73],twohaploidgametescombineto

generatediploidcellinwhicheachchromosomepairconsistsofamaternalandpaternalchromosome.

18.TheDNAofchromatinandchromosomesisboundtightlytoafamilyofpositivelychargedproteins,thehistones[74],whichassociatestronglywiththemanynegativelychargedphosphategroupsinDNA.AbouthalfthemassofchromatinisDNAandhalfishistones.WhenDNAreplicatespriortocelldivision,largequantitiesofhistonesarealsosynthesizedtomaintainthis1:1massratio.ThehistonesandDNAassociateincomplexescallednucleosomes[75],inwhichtheDNAstrandwindsaroundacoreofhistonemolecules.TheDNAofasinglehumanchromosomeformsaboutamillionnucleosomes;nucleosomesassociatetoformveryregularandcompactsupramolecularcomplexes.Theresultingchromatinfibers[76],about30nmindiameter,condensefurtherbyformingaseriesofloopedregions,whichclusterwithadjacentloopedregionstoformthechromosomesvisibleduringcelldivision.ThistightpackingofDNAintonucleosomesachievesaremarkablecondensationoftheDNAmolecules.TheDNAinthechromosomesofasinglediploidhumancellwouldhaveacombinedlengthofabout2miffullyextendedasaDNAdoublehelix,butthecombinedlengthoftheall46chromosomesisonlyabout200μm.

MitochondriaArethePowerPlantsofAerobicEukaryoticCells19.Mitochondriaareveryconspicuous[77]inthecytoplasmofmosteukaryoticcellswhen

viewedbyelectronmicroscope.Thesemembraneboundedorganellesvaryinsize,but

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typicallyhaveadiameterofabout1μm,similartothatofbacterialcells.Mitochondriaalsovarywidelyinshape,number,andlocation,dependingonthecelltypeortissuefunction.Mostplantandanimalcellscontainseveralhundredtoathousandmitochondria.Generally,cellsinmoremetabolicallyactivetissuesdevotealargerproportionoftheirvolumetomitochondria.Each mitochondrionhastwomembranes.Theoutermembraneisunwrinkledandcompletelysurroundstheorganelle.Theinnermembranehasinfoldingscalledcristae[78],whichgiveitalargesurfacearea.Enclosedbytheinnermembraneisthematrix[79],averyconcentratedaqueoussolutionofenzymesandchemicalintermediatesinvolvedinenergyyieldingmetabolism.

20.Mitochondrialenzymescatalyzetheoxidationoforganicnutrientsbymolecularoxygen(O2);someoftheseenzymesareinthematrixandsomeareembeddedintheinnermembrane.ThechemicalenergyreleasedinmitochondrialoxidationsisusedtogenerateATP,themajorenergycarryingmoleculeofcells.Inaerobiccells,mitochondriaarethe

principalproducersofATP,whichdiffusestoallpartsofthecellandprovidestheenergyforcellularwork.Unlikeothermembranousstructuressuchaslysosomes,Golgicomplexes,andthenuclearenvelope,mitochondriaareproducedonlybydivisionofpreviouslyexistingmitochondria;eachmitochondrioncontainsitsownDNA,RNA,andribosomes.MitochondrialDNAcodesforcertainproteinsspecifictothemitochondrialinnermembrane.Thisandotherevidencesupportsthetheorythatmitochondriaarethedescendantsofaerobicbacteriathatlivedendosymbiotically[80]withearlyeukaryoticcells.

ChloroplastsConvertSolarEnergyintoChemicalEnergy21.Thecytoplasmofplantscontainsplastids[81],specializedorganellessurroundedbyenvelopesconsistingoftwomembranes.Mostconspicuousoftheplastidsandcharacteristicallypresentinthephotosyntheticcellsofplantsandalgae[82]arethechloroplasts.

22.Likemitochondria,thechloroplastsmaybeconsideredpowerplants,withtheimportantdifferencethatchloroplastsusesolarenergy,whereasmitochondriausethechemicalenergyofoxidizablecompounds.PigmentmoleculesinchloroplastsabsorbtheenergyoflightanduseittomakeATPand,ultimately,toreducecarbondioxidetoformcarbohydratessuchasstarchandsucrose.Photosynthesisineukaryotesandincyanobacteria[83]producesO2asabyproductofthelightcapturingreactions;Photosyntheticplantcellscontainbothchloroplastsandmitochondria.ChloroplastsproduceATPonlyinthelight;mitochondriafunctionindependentlyoflight,oxidizingcarbohydratesgeneratedbyphotosynthesisduringdaylighthours

23.Chloroplastsaregenerallylarger(diameter5μm)thanmitochondriaandhavevariousshapes.Becausechloroplastscontainahighconcentrationofthepigmentchloro

phyll[84],cellsareusuallygreen,buttheircolordependsontherelativeamountsofotherpigmentspresent.Chlorophyllandotherpigmentmolecules,whichtogethercanabsorblightenergyovermuchofthevisiblespectrum,arelocalizedintheinternalmem

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branesofthechloroplast;thesemembranesformstacksofclosedcisternaeknownasthylakoids[85].Likemitochondria,chloroplastscontainDNA,RNA,andribosomes.

 Notes

[1]extracellular[9ekstr[5seljUl[]fluid细胞外液

[2]hormone[`hR:m[Un]n.激素

[3]neurotransmitter[9nju[r[u5trAnsmit[]n.神经递质

[4]antigen[`AntidV[n]n.抗原

[5]signalreceptor信号受体

[6]receptorligand[5lig[nd`laig[nd]受

体配体

[7]intracellular[9intr[5seljul[]adj.细

胞内的

[8]ionchannel[5ai[5tFAnl]离子通道

[9]acetylcholine[[7si:t[5[ulin]n.乙酰

胆碱

[10]cascade[kAs5keid]n.小 瀑 布,人 工

瀑布,分多级进行

[11]lipoprotein[7lip[5pr[uti:n]n.脂蛋白

[12]antibody[5Anti7bRdi]n.抗体

[13]mosaic[mC5zeiik]n.镶 嵌,镶 嵌 图

案,镶嵌工艺

[14]molecularantenna[An5ten[]分 子 天

线

[15]cellulose[5seljUl[us]n.纤维素

[16]invaginate[in5vAdVinneit]v.收进鞘

中,套进内部

[17]vesicle[5vesikl]n.[解][动]囊,泡,[植]小泡

[18]endosome[5end[9s[Um]n.内吞体

[19]phagocytosis[fAg[7sait[Usis]n.噬

菌作用

[20]phagosome[5fAg[s[Um]n.吞噬体

[21]particulate[p[5tikjulit]adj.微粒的

[22]peroxisome[p[5rRksis[um]n.过 氧

化物酶体

[23]convolute[5kCnv[ljut]v.回 旋,卷

绕,盘旋adj.旋绕的

[24]subcellularcompartment[5sQb5seljul[k[n5pB:tm[nt]亚细胞隔室

[25]lumen[5lju:mi:n]n.流明(光通量单

位),[解]内腔

[26]cisternae[5sisten[]n.扁囊,池,封闭

的膜系统及其围成的腔构成网状膜结

[27]pancreatic[9pANkri5Atik]adj.胰腺

[28]insulin[5insjulin]n.胰岛素

[29]roughendoplasmicreticulum [5end[U9plAzmikri5tikjul[m]粗面内质网

[30]smoothendoplasmicreticulum光 滑 内

质网

[31]tubular[5tju:bjUl[]adj.管状的

[32]skeletalmuscle[5skelitl5mQsl]n.骨

骼肌

[33]asymmetric[Asi5metrik]adj.不对称

[34]sort[sC:t]v.分类,拣选

[35]cisside顺式面(面向内质网的一面)[36]transside反式面(面向质膜的一面)[37]bud出芽

[38]moiety[5mCi[ti]n.一 部 分;组 成 部

分,成分

[39]secretory granule [si5kri:t [ri5grAnju:l]n.分泌颗粒

[40]lysosome[5lais[us[um]n.溶酶体

[41]polysaccharide[pRli5sAk[raid]n.多

[42]nucleicacid[5nju:kliik5Asid]n.核

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[43]recyclingcenter[5ri:5saikliN5sent[]

n.废物利用中心

[44]monosaccharide[7mCn[u5sAk[raid]

n.单糖

[45]catabolize[k[5tAb[9laiz]v.(使)异

化,(使)发生分解代谢

[46]protonpump[5pr[utRnpQmp]n.质

子泵

[47]centralvacuole[sen`tra:l5vAkju[ul]中央大液泡

[48]tonoplast[5tRn[9plB:st]n.(包 围 植

物细胞液泡的)液泡膜

[49]anthocyanin[9AnW[5sai[nin]n.花青

[50]osmotically[Rz5mRtikli]adv.渗 透

的,渗透性的

[51]turgorpressure[5t[:g[5preF[]n.膨

[52]hydrogenperoxide[5haidr[udV[np[5rCksaid]过氧化氢

[53]glyoxysome[7gli5Rks[um]n.乙醛酸

循环体

[54]freeradical[5rAdidl]自由基

[55]catalase[5kAt[leis]n.过氧化氢酶,触酶

[56] glyoxylate cycle [glai5Cksi7leit5saikl]乙醛酸循环

[57]microbody[5maikr[u9bCdi]n.微体

[58]nucleoplasm [5njU:kli[plAzm]n.核

[59]nuclearporecomplex核孔复合物

[60]diffusematerial[di5fju:zm[5ti[ri[l]弥散性物质

[61]chromatin[5kr[um[tin]n.染色质

[62]nucleolus[nju:5kli:[l[s]n.核仁

[63]mitosis[mi5t[usis]n.有丝分裂,核分

[64]cytokinesis[7sait[ukai5ni:sis]n.细

胞质分裂

[65]chromosome[5kr[um[s[um]n.染色

[66]chromatid[5kr[um[tid]n.染色单体

[67]protist[5pr[utist]n.原生生物

[68] Tetrahymena pyriformis [9tetr[5haimEn[5pirifR:mis]四膜虫

[69]Ophioglossumreticulatum 心脏叶瓶尔

小草,瓶尔小草

[70]diploid(2n)[5diplRid]n.二倍体

[71]gamete[5gAmi:t]n.配子

[72]meiosis[mai5[usis]n.减数分裂

[73]sexualreproduction[5seksju[l7ri:pr[5dQkF[n]有性繁殖

[74]histone[5hist[un]n.组蛋白

[75]nucleosome[5nju:kli[s[um]n.核 小

[76]chromatinfiber染色质纤维

[77]conspicuous[k[n5spikju[s]adj.显著

的,显眼的

[78]cristae[5krist[]n.嵴

[79]matrix[5meitriks]n.(线粒体)基质

[80]endosymbioticallyadv.内共生地

[81]plastid[5plAstid]n.质体

[82]algae[5AldVi:]n.藻类,海藻

[83]cyanobacteria[5sai[n[bAkti[ri[]n.蓝细菌

[84]chlorophyll[5klC:r[fil]n.叶绿素

[85]thylakoid[5Wail[9kRid]n.类囊体

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1.Protoplasmisuniquenotonlybecauseitconsistsofhighlycomplexandspecialmoleculesbutalsobecauseofitsphysicalnature,becauseofitshighviscosity[1],protoplasmisabitlikegelatin[2]orsometimeslikeglue[3].Thephysicalnatureofprotoplasmisdeterminedbyvastareasofinterface[4]betweensomeofthosespecialmolecules,especiallyproteins,andtheprotoplasmicsolutionsinwhichtheyaresuspended.Thereactionsoflifearecatalyzedattheseenzymeinterfaces.Soilsarealsocharacterizedbyhugeinterfacesbetweenclay[5]andtoalessextent,silt[6]andsandorhumus[7]particlesandtheirsurroundings.Technologytakesadvantageofsuchsystemsinwatersofteners,

catalyticconvertersandnumerousotherapplications.2.Crucialtothephysicalnatureofprotoplasmaremembranesandparticlestoosmalltosettleout[8]bygravitybutlargerthantheatoms,smallmolecules,andionsthatformtruesoluteparticles.Whentheselargerparticlesaresuspendedinwater,theysometimesformglue,sotheyhavebeentermedcolloids,fromtheGreekwordkola,“glue”.

3.Whydocolloidsnotsettleout?Becausetheyareconstantlybeingstruckbythesurroundingmuchsmallerwatermoleculesinrapidmotion,andtheyaresmallenoughthattherandomvelocitiesoftheimpactingwatermoleculesdonotaverageout[9].Atanygivenmomentthereisahighprobabilitythatacolloidalparticleisbombardedmorestronglyononesidethanontheoppositeside.Whencolloidalparticlesareobservedinalightmicroscopebystrongilluminationfromoneside,theyappearaspointsoflight(theTyndalleffect[10],firstnoticedbyJohnTyndall,1820~1893).Theyseemtodancearoundwithmanyrandomhopspersecond.Thelargest(brightest)particlesdancelessthanthesmaller(dimmer)particles.

4.ThisisBrownianmovement[11],discoveredbytheScottishbotanistRobertBrownin1827.Itisbeautiful,evenspectacular,confirmationofkinetictheory.Thiserratic(irregular)andcontinuousmotionkeepscolloidsfromsettling.Indeed,wemightdefineacolloidalparticleasonethatisnotatruesolute[12]butissmallenoughtoremaininsus

pensionbecauseofitsBrownianmovement.Withslightlylargerparticles,thereisamuchgreaterchancethattherandombombardmentonanysidewillapproachanaveragevaluefortheentireparticle.Inthecontestbetweenkineticbombardmentandgravity,

gravitywins,sotheparticlesettles.5.ThelargestparticlesexhibitingBrownianmovementareabout100to2,000nmindiameter,dependingonshapesanddensities.Becauselightwavesare385to776nmlong,onlythelargestcolloidalparticlescancastshadows[13].Thesmallestonesrefractlightwaves,causingtheTyndalleffect,butarenotthemselvesactuallyvisibleinalightmicroscope.Smallerparticlesaretruesolutes,butthedistinctionisnotprecise.Manyparticlesinacell,includingtheribosomesandallthesingleproteinmoleculesthatare

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enzymes,areinthecolloidalsizerange.6.Mostcolloidalparticlespassthroughfilterpaper[14],buttheycannotpassthroughcellophane[15],ascantruesoluteparticles.Suspensionparticlesaretoolargetopassthroughfilterpaper.Althoughcolloidalparticlesaresmall,eachislargeenoughtopresentasurface(alayerofatoms)tosurroundingwatermoleculesandsoluteparticles.Becauseofthesmallsizeofcolloidalparticles,theirtotalsurfaceinagivenvolumeisrelativelyhuge.Imagineasolidcubeofmaterial1cmoneachofitsedges.Therearesixfaces,soithasasurfaceareaof6cm2.Cutitonce,youexpose2cm2 moresurfaces.Continueslicingthecubeuntilyouhavereducedeachparttoacubeof10nmlongonitsedges.Nowthetotalsurfaceareais6000000cm2(600m2).Asinglecubewiththesamesurfaceareawouldbe10mhighwithavolumeof1000m3!Colloidalparticlesareseldomcubes,buttheyareofcomparativesize.

7.Thereactionsoflifeoccuronsurfaces,anditiseasytoseehowrelativelylargesurfacescanexistinasinglecell.Itisalsoeasytoseehowhydration(matricforces[16])caninfluencethewatermilieu(backgroundorsurroundings)ofcellsandsoils.

 Notes

[1]viscosity[vis5kCsiti]n.黏度,黏性

[2]gelatin[5dVel[tin]n.明胶

[3]glue[glU:]n.胶,胶水

[4]interface[5int[7feis]n.分界面

[5]clay[klei]n.黏土;泥土

[6]silt[silt]n.淤泥

[7]humus[5hju:m[s]n.腐殖土

[8]settleoutv.沉降

[9]averageoutv.达到平衡

[10]Tyndalleffect丁达尔效应

[11]Brownianmovement布朗运动

[12]truesolute[trU:5sCljU:t]真溶质

[13]castshadow投下阴影

[14]filterpaper滤纸

[15]cellophane[5sel[fein]n.玻璃纸; 璐

[16]matricforce基质作用力

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犝犖犐犜03 犅犐犗犆犎犈犕犐犛犜犚犢

犈狊狊犪狔06 犆犲犾犾狊犪狀犱犜犻狊狊狌犲狊犝狊犲犱犻狀犅犻狅犮犺犲犿犻犮犪犾犛狋狌犱犻犲狊

1.Becausealllivingcellshaveevolvedfromthesameprogenitors[1],theysharecertainfundamentalsimilarities.CarefulBiochemicalstudyofjustafewtypesofcells,howeverdifferentinbiochemicaldetailsandvariedinsuperficialappearance,shouldtherefore

yieldgeneralprinciplesapplicabletoallcellsandorganisms.Theburgeoning[2]ofbiologicalknowledgeoverthepast150yearshasrepeatedlysupportedthesepropositions[3].Certaincells,tissues,andorganismshaveprovenmoreamenable[4]toexperimentalstudiesthanothers.Knowledgeinbiochemistryisderivedprimarilyfromafewrepresentativetissuesandorganisms,suchasthebacteriumE.coli,theyeastSaccharomycescerevisae[5],photosyntheticalgaesuchaschlamydomonas[6],spinach[7]leaves,

ratliver,andtheskeletalmuscleofseveralvertebrates[8].Somebiochemicalstudiesfocusontheisolation,purification,andcharacterizationofcellularcomponents;otherresearchinvestigatesthemetabolicandgeneticpathwaysoflivingcells.

2.Anexperimenterideallybeginstheisolationofenzymesandothercellularcomponentswithplentifulandhomogeneous[9]sourceofthematerial.Thecomponentofinterestoftenrepresentsonlyaminuscule[10]fractionofthetotalmaterial,andgramsorevenkilo

gramsofstartingmaterialareneededtoobtainafewmicrogramsofthepurifiedcomponent.Ahomogeneoussourceofanenzymeornucleicacid,inwhichallthecellsaregeneticallyandbiochemicalidentical,leavesnodoubtaboutwhichcelltypeyieldedthe

purifiedcomponentandmakesitsafertoextrapolate[11]theresultsofinintrostudiestothesituationinvivo.Alargecultureofbacterialcells,allderivedbydivisionfromthesameparentandthereforegeneticallyidentical,meetstherequirementforaplentifulandhomogeneoussource.Individualtissuesfromlaboratoryanimals(ratliver,pigbrain,rabbitmuscle)areplentifulsourcesofsimilar,thoughnotidentical,cells.Someanimalandplantcellsproliferate[12]incellculture,producingpopulationsofidentical(cloned)cellsinquantitiessuitableforbiochemicalanalysis.

3.Geneticmutants[13]inwhichadefectinasinglegeneproducesadefectiveprotein[14],

whichcausesaspecificfunctionaldefectinthecellororganism,areextremelyusefulinestablishingthatacertainproteinisessentialtoaparticularcellularfunction.Becauseitistechnicallymuchsimplertoproduceanddetectmutantsinbacteriaandyeast,theseorganisms(E.coliandS.cerevisae,forexample)havebeenfavoriteexperimentaltar

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getsforbiochemicalgeneticists[15].Oncethegeneforaproteinhasbeenisolated,itcanoftenbeinsertedintoabacterialoryeastcell,whichthenactsasabiologicalfactory[16],

overproducing[17]theprotein.Withgeneticengineering[18]techniques,experimenterscanintroducespecificmutationsintosuchgenesanddeterminetheireffectsonproteinstructureandfunction.

4.Anorganismthatiseasytocultureinthelaboratory,andhasashortgenerationtime[19],offerssignificantadvantagestotheresearchbiochemist.Anorganismthatrequiresonlyafewsimpleprecursormoleculesinitsgrowthmediumcanbeculturedinthepresenceofaradioisotopicallylabeled[20]precursor,andthemetabolicfateofthatprecursorcanthenbeconvenientlytracedbyfollowingtheincorporationoftheradioactiveatomsintoitsmetabolicproducts.Theshortgenerationtimeofmicroorganisms(minutesorhours)allowstheinvestigatortofollowalabeledprecursororageneticdefectthroughmanygenerationsinafewdays.Inorganismswithgenerationtimesofmonthsoryears,thisisvirtuallyimpossible.

5.Somehighlyspecializedtissuesofmulticellularorganismsareremarkablyenrichedinsomeparticularcomponentrelatedtotheirspecializedfunction.Forstudiesonsuchspecificcomponentsorfunctions,biochemistscommonlychoosethespecializedtissuefortheirexperimentalsystems.Forexample,vertebrateskeletalmuscleisarichsourceofactin[21]andmyosin[22];pancreaticsecretorycellscontainhighconcentrationsofroughendoplasmicreticulum;spermcellsarerichinDNA;livercontainshighconcentrationsofmanyenzymesofbiosyntheticpathways;andspinachleavescontainlargenumbersofchloroplasts.

6.Sometimes,itissimplicityofstructurethatmakesaparticularcellororganismattractiveasanexperimentalsystem.Forstudiesonplasmamembranestructureandfunction,thematureredbloodcellhasbeenafavorite,becauseithasnointernalmembranes[23]tocomplicatepurificationoftheplasmamembrane.Somebacterialviruses(bacteriophages[24])havefewgenes.TheirDNA moleculesarethereforesmallerandmuchsimplerthanthoseofhumansormaizeplants.IthasprovedeasiertostudyDNAreplicationwiththesevirusesthanwitheukaryoticchromosomesbecausewhenavirusinfectsabacterialcell,thereisasynchronousburst[25]ofDNAsynthesis,oftenaccompaniedbyincreasedlevelsoftheenzymesofDNAreplication.

 Notes

[1]progenitor[pr[5dVenit[]n.祖先

[2]burgeon[5b…dV[n]v.萌发

[3]proposition[9prRp[5ziF[n]n.主张,建议,陈述,命题

[4]amenable[[5mi:n[bl]adj.经得起检

验的;可 按 照……控 制[处 理,测 验]的

[5]Saccharomycescerevisaen.酵母

[6]chlamydomonas[9klAmid[5m[un[s]

n.衣藻

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[7]spinach[5spinidV5spinitF]n.菠菜

[8]vertebrate[5v[:tibrit]n.脊椎动物

[9]homogeneous[9hRm[u5dVi:nj[s]

adj.同质的

[10]minuscule[mi5nQskju:l]adj.极小的

[11]extrapolate[eks5trAp[leit]v.外 推,推断

[12]proliferate[pr[u5lif[reit]v.增 生 扩

[13]mutant[5mju:t[nt]n.突变体

[14]defective[di5fektiv]protein缺陷蛋白

[15]geneticist[dVi5netisist]n.遗传学家

[16]biologicalfactory生物工厂

[17]overproduce[5[uv[pr[5dju:s]v.超

量生产

[18] genetic engineering [dVi5netik7endVi5ni[riN]遗传工程

[19]generationtime世代

[20]radioisotopicallylabeled[5reidi[u7ais[U5tCpikli5leibld]放 射 性 同 位 素 标

记的

[21]actin[5Aktin]n.肌动蛋白

[22]myosin[5mai[sin]n.肌球蛋白

[23]internalmembrane内膜

[24]bacteriophage[bAk5ti[ri[feidV]n.噬菌体

[25]synchronousburst[5siNkr[n[sb[:

st]同步突发

犈狊狊犪狔07 犜犺犲αHelix[1]IsaCommonProteinSecondaryStructure[2]

1.PaulingandCoreywereawareoftheimportanceofhydrogenbondsinorienting[3]polarchemicalgroup ssuchasthe C O and N H groupsofthepeptidebond.TheyalsohadtheexperimentalresultsofWilliamAstbury,whointhe1930shadconductedpioneering[4]Xraystudiesofproteins.Astburydemonstratedthattheproteinthatmakesuphairandporcupinequills[5](thefibrousproteinαkeratin[6])hasaregularstructurethatrepeatsevery5.15to5.2.[Theangstrom[7], (namedafterthephysicistAndersJ.ngstrm),isequalto0.1nm.AlthoughnotanSIunit[8],itisuseduniversallybystructuralbiologiststodescribeatomicdistances.]Withthisinformationandtheirdataonthepeptidebond[9],andwiththehelpofpreciselyconstructedmodels,PaulingandCoreysetouttodeterminethelikelyconformations[10]ofproteinmolecules.

2.Thesimplestarrangementthepolypeptidechain[11]couldassume[12]withitsrigid[13]

peptidebonds(butothersinglebondsfreetorotate)isahelicalstructure,whichPaulingandCoreycalledtheαhelix.Inthisstructurethepolypeptidebackboneistightlywound[14]aroundanimaginaryaxisdrawnlongitudinally[15]throughthemiddleofthehelix,andtheRgroupsoftheaminoacidresidues[16]protrude[17]outwardfromthehelicalbackbone.Therepeatingunit[18]isasingleturnofthehelix,whichextendsabout5.4alongthelongaxis,slightlygreaterthantheperiodicity[19]AstburyobservedonXrayanalysisofhairkeratin.Theaminoacidresiduesinαhelixhaveconformationswithψ=-45°to-50°andφ=-60°,andeachhelicalturnincludes3.6aminoacidresidues.Thehelicaltwistofαhelixfoundinallproteinsisrighthanded.Theαhelix

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provedtobethepredominant[20]structureinαkeratins.Moregenerally,aboutonefourthofallaminoacidresiduesinpolypeptidesarefoundinαhelices,theexactfractionvaryinggreatlyfromoneproteintothenext.Whydoestheαhelixformmorereadilythanmanyotherpossibleconformations?Theansweris,inpart,thatanαhelixmakesoptimaluseofinternalhydrogenbonds.Thestructureisstabilizedbyahydrogenbondbetweenthehydrogenatomattachedtotheelectronegative[21]nitrogenatomofthepeptidelinkageandtheelectronegativecarbonyloxygenatomofthefourthaminoacidontheaminoterminalsideofthatpeptidebond.Withinαhelix,everypeptidebond(exceptthoseclosetoeachendofthehelix)participatesinsuchhydrogenbonding.Eachsuccessiveturnoftheαhelixisheldtoadjacentturnsbythreetofourhydrogenbonds.Allthehydrogenbondscombinedgivetheentirehelicalstructureconsiderablestability.

3.Furthermodelbuildingexperiments[22]haveshownthatαhelixcanforminpolypeptidesconsistingofeitherLorDaminoacids.However,allresiduesmustbeofonestereoisomeric[23]series;aDaminoacidwilldisruptaregularstructureconsistingofLaminoacids,andviceversa.NaturallyoccurringLaminoacidscanformeitherrightorlefthandedαhelices,butextendedlefthandedheliceshavenotbeenobservedinproteins.

AminoAcidSequenceAffectsαHelixStability4.Notallpolypeptidescanformastableαhelix.Interactionsbetweenaminoacidsidechainscanstabilizeordestabilize[24]thisstructure.Forexample,ifapolypeptidechainhasalongblockof[25]glutamate(Glu)[26]residues,thissegmentofthechainwillnotformαhelixatpH7.0.ThenegativelychargedcarboxylgroupsofadjacentGluresiduesrepeleachothersostronglythattheyovercomethestabilizinginfluenceofhydrogenbondsontheαhelix.Forthesamereason,iftherearemanyadjacentlysine(Lys)[27]and/orarginine(Arg)[28]residues,whichhavepositivelychargedRgroupsat

pH7.0,theywillalsorepeleachotherandpreventformationoftheαhelix.Thebulkandshapeofasparagine(Asn)[29],serine(Ser)[30],threonine(Thr)[31],andcysteine(Cys)[32]residuescanalsodestabilizeanαhelixiftheyareclosetogetherinthechain.

5.Thetwistofαhelixensuresthatcriticalinteractionsoccurbetweenaminoacidsidechainandthesidechainthree(andsometimesfour)residuesawayoneithersideofit.Positivelychargedaminoacidsareoftenfoundthreeresiduesawayfromnegativelychargedaminoacids,eliminatingtheformationofanionpair.Twoaromaticaminoacid[33]residuesareoftensimilarlyspaced,avoidingahydrophobicinteraction.Aconstraintontheformationofαhelixisthepresenceofproline (Pro)[34]orglycine(Gly)[35]residues.Inproline,thenitrogenatomispartofarigidringandrotationa

boutthe N Ca bondisnotpossible.Thus,aProresidueintroducesadestabilizingkink[36]inαhelix.Inaddition,thenitrogenatomofProresidueinpeptidelinkagehasnosubstituenthydrogentoparticipateinhydrogenbondswithotherresidues.Forthesereasons,prolineisonlyrarelyfoundwithinαhelix.Glycineoccursinfrequentlyinαhelicesforadifferentreason:ithasmoreconformationalflexibilitythantheotheramino

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acidresidues.Polymersofglycinetendtotakeupcoiledstructurequitedifferentfromαhelix.Afinalfactoraffectingthestabilityofαhelixinapolypeptideistheidentityoftheaminoacidresiduesneartheendsoftheαhelicalsegment.Asmallelectricdipole[37]

existsineachpeptidebond.Thesedipolesareconnectedthroughthehydrogenbondsofthehelix,resultinginanetdipoleextendingdownthehelixthatincreaseswithhelixlength.Thefouraminoacidresiduesateachendofthehelixdonotparticipatefullyinthehelixhydrogenbonds.Thepartialpositiveandnegativechargesofthehelixdipoleactuallyresideonthepeptideaminoandcarbonylgroupsneartheaminoterminalandthecarboxylterminalendsofthehelix,respectively.Forthisreason,negativelychargedaminoacidsareoftenfoundneartheaminoterminusofthehelicalsegment,

wheretheyhavestabilizinginteractionwiththepositivechargeofthehelixdipole;apotivelychargedaminoacidattheaminoterminalendisdestabilizing.Theoppositeistrueatthecarboxylterminalendofthehelicalsegment.Thusfivedifferentkindsofconstraintsaffectthestabilityofαhelix:

(1)Theelectrostaticrepulsion(orattraction)betweensuccessiveaminoacidresidueswithchargedRgroups.

(2)Thebulkinessofadjacentgroups.(3)Theinteractionsbetweenaminoacidsidechainsspacedthree(orfour)residuesapart(4)TheoccurrenceofProandGlyresidues.(5)Theinteractionbetweenaminoacidresiduesattheendsofthehelixsegmentandtheelectricdipoleinherenttotheahelix.

 Notes

[1]αhelix[5hi:liks]α螺旋

[2]secondarystructure二级结构

[3]orient[5R:ri[nt]v.定向

[4]pioneer[9pai[5ni[]v.开 路,创 办;打

开(新领域)或准备(途径)[5]porcupinequill[5pR:kjupainkwil]n.(豪猪、刺猬的)刚毛

[6]αkeratin[5ker[tin]n.α角蛋白

[7]angstrom[5ANstr[m]n.()埃(长

度单位)[8]SIunit:SystèmeInternationalUnit

国际(单位)制[9]peptidebond[5peptaidbRnd]n.肽键

[10]conformation[7kRnfR:5meiF[n]n.构象

[11]polypeptidechain[9pRli5peptaidtFein]

n.多肽链

[12]assume[[5sju:m]vt.采取,呈现

[13]rigid[5ridVid]adj.刚性的

[14]wind[waind]v.绕,缠,上 发 条,旋

[15]longitudinally [lRndVi5tju:din[li]

adj.经度的,纵向的

[16]residue[5rezidju:]n.残基

[17]protrude[pr[5tru:d]v.伸出

[18]repeatingunit重复单位

[19]periodicity[9pi[ri[5disit]n.周期性

[20]predominant[pri5dRmin[nt]adj.卓

越的,支配的,主要的,突出的,有影

响的

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[21]electronegative [i9lektr[u5neg[tiv]

adj.电负性的

[22]modelbuildingexperiment建模实验

[23]stereoisomeric[7sti[ri[u5ais[m[rik]

adj.立体异构体的

[24]destabilize[di:5steibilaiz]vt.去稳定

[25]alongblockof一长串的

[26]glutamate(Glu)[5glu:t[meit]n.谷

氨酸

[27]lysine(Lys)[5laisi:n]n.赖氨酸

[28]arginine(Arg)[5B:dVinin]n.精氨酸

[29]asparagine(Asn)[[s5pAr[dVi:n]n.

天冬酰胺

[30]serine(Ser)[5seri:n]n.丝氨酸

[31]threonine(Thr)[5Wri:[ni:n]n.苏

氨酸

[32]cysteine(Cys)[5sistin]n.半胱氨酸

[33]aromatic[7Ar[U5mAtik]aminoacid芳香氨基酸

[34]proline(Pro)[5pr[uli:n]n.脯氨酸

[35]glycine(Gly)[5glaisi:n]n.甘氨酸

[36]kink[kiNk]n.结节

[37]electricdipole[i5lektrik5daip[ul]n.电偶极

犈狊狊犪狔08 犇犖犃犐狊犪犇狅狌犫犾犲犎犲犾犻狓[1]

1.Toshedmorelighton[2]thestructureofDNA,RosalindFranklinandMauriceWilkinsusedthepowerfulmethodofXraydiffraction[3]toanalyzeDNAfibers.Theyshowedintheearly1950sthatDNAproducesacharacteristicXraydiffractionpattern.Fromthis

patternitwasdeducedthatDNAmoleculesarehelicalwithtwoperiodicitiesalongtheirlongaxis,aprimaryoneof3.4andasecondaryoneof34.Theproblemthenwastoformulate[4]athreedimensionalmodeloftheDNAmoleculethatcouldaccountnotonlyfortheXraydiffractiondatabutalsoforthespecificA = TandG = Cbasee

quivalences[5]discoveredbyChargaffandfortheotherchemicalpropertiesofDNA.2.In1953,WatsonandCrickpostulated[6]athreedimensionalmodelofDNAstructurethataccountedforalltheavailabledata.ItconsistsoftwohelicalDNAchainswoundaroundthesameaxistoformarighthandeddoublehelix.Thehydrophilic[7]backbonesofalternatingdeoxyribose[8]andphosphategroupsareontheoutsideofthedoublehelix,facingthesurroundingwater.Thefuranose[9]ringofeachdeoxyriboseisintheC2’endoconformation[10].Thepurine[11]andpyrimidine[12]basesofbothstrandsarestacked[13]insidethedoublehelix,withtheirhydrophobicandnearlyplanarringstructuresveryclosetogetherandperpendiculartothelongaxis.Theoffsetpairingofthetwostrandscreatesamajorgroove[14]andminorgroove[15]onthesurfaceoftheduplex.Eachnucleotidebaseofonestrandispairedinthesameplanewithabaseoftheotherstrand.WatsonandCrickfoundthatthehydrogenbondedbasepairs,GwithCandAwithT,arethosethatfitbestwithinthestructure,providingarationale[16]forChar

gaff’srulethatinanyDNA,G=CandA= T.ItisimportanttonotethatthreehydrogenbondscanformbetweenGandC,butonlytwocanformbetweenAandT.ThisisonereasonforthefindingthatseparationofpairedDNAstrandsismoredifficult

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thehighertheratioofGCtoATbasepairs.Otherpairingsofbasestend(tovaryingdegrees)todestabilizethedoublehelicalstructure.WhenWatsonandCrickconstructedtheirmodel,theyhadtodecideattheoutsetwhetherthestrandsofDNAshouldbeparallelorantiparallel[17]— whethertheir5’,3’phosphodiesterbonds[18]shouldruninthesameoroppositedirections.Antiparallelproducedthemostconvincingmodel,andlaterworkwithDNApolymerases[19]providedexperimentalevidencethatthestrandsareindeedantiparallel,afindingultimatelyconfirmedbyXrayanalysis.

3.ToaccountfortheperiodicitiesobservedintheXraydiffractionpatternsofDNAfibers,WatsonandCrickmanipulatedmolecularmodelstoarriveatastructureinwhichtheverticallystackedbasesinsidethedoublehelixwouldbe3.4apart;thesecondaryrepeatdistanceofabout34wasaccountedforbythepresenceof10basepairsineachcompleteturnofthedoublehelix.Inaqueoussolutionthestructurediffersslightlyfromthatinfibers,having10.5basepairsperhelicalturn.ThetwoantiparallelpolynucleotidechainsofdoublehelicalDNAarenotidenticalineitherbasesequenceorcomposition.Insteadtheyarecomplementary[20]toeachother.Whereveradenine[21]occursinonechain,thymine[22]isfoundintheother;similarly,whereverguanine[23]occursinonechain,cytosine[24]isfoundintheother.TheDNAdoublehelixorduplexisheldtogetherbytwoforces,asdescribedearlier:hydrogenbondingbetweencomplementarybasepairsandbasestackinginteractions[25].ThecomplementaritybetweentheDNAstrandsisattributabletothehydrogenbondingbetweenbasepairs.Thebasestackinginteractions,whicharelargelynonspecific[26]withrespecttotheidentityofthestackedbases,makethemajorcontributiontothestabilityofthedoublehelix.TheimportantfeaturesofthedoublehelicalmodelofDNAstructurearesupportedbymuchchemicalandbiologicalevidence.Moreover,themodelimmediatelysuggestedamechanismforthetransmission[27]ofgeneticinformation.TheessentialfeatureofthemodelisthecomplementarityofthetwoDNAstrands.AsWatsonandCrickwereabletosee,wellbeforeconfirmatorydatabecameavailable,thisstructurecouldlogicallybereplicatedby(1)separatingthetwostrandsand(2)synthesizingacomplementarystrandforeach.Becausenucleotidesineachnewstrandarejoinedinasequencespecifiedbythebasepairingrulesstatedabove,eachpreexisting[28]strandfunctionsasatemplatetoguidethesynthesisofonecomplementarystrand.Theseexpectationswereexperimentallyconfirmed,inaugurating[29]arevolutioninourunderstandingofbiologicalinheritance.

 Notes

[1]doublehelix[5dQbl5hi:liks]双螺旋

[2]toshedmorelighton更好地说明

[3]Xraydiffraction[di5frAkF[n]X射

线衍射

[4]formulate[5fR:mjuleit]vt.把……作

成公式,用公式表示

[5]baseequivalence[i5kwiv[l[ns]碱 基

等价关系

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[6]hydrophilic[7haidr[u5filik]adj.亲

水的

[7]deoxyribose[di:9Rksi5raib[us]n.脱

氧核糖

[8]furanose[5fju[r[7n[us]n.呋喃糖

[9]endoconformation内向构象

[10]purine[5pju[ri:n]n.嘌呤

[12]pyrimidine[5pirimidi:n]n.嘧啶

[13]stack[stAk]v.堆积

[14]majorgroove[5meidV[gru:v]n.大

[15]minorgroove[5main[gru:v]n.小沟

[16]rationale[7rAF[5nB:li]n.理论基础,合逻辑的论据

[17]antiparallel[9Anti5pAr[lel]adj.反

平行的

[18]phosphodiesterbond[f[usf[dai5est[

bRnd]磷酸二酯键

[19]DNApolymerase[5pRlim[5reis]n.DNA聚合酶

[20]complementary[kRmpl[5ment[ri]n.互补的

[21]adenine[5Ad[ni:n]n.腺嘌呤

[22]thymine[5Waimi:n]n.胸腺嘧啶

[23]guanine[5gwB:ni:n]n.鸟嘌呤

[24]cytosine[5sait[si:n]n.胞嘧啶

[25]basestackinginteraction碱基堆积力

[26]nonspecific[5nRnspi5sifik]adj.非特

异的

[27]transmission[trAnz5miF[n]n.传递

[28]preexist[5pri:ig5zist]v.事先存在

[29]inaugurate[i5nR:gjureit]vt.举 行 就

职典礼,创新,开辟,举行开幕(落成、成立)典礼

犈狊狊犪狔09 犚犲犪犮狋犻狅狀狊狅犳狋犺犲犆犻狋狉犻犮犃犮犻犱犆狔犮犾犲[1]

1.Aswehaveknownthat,theendproductofglycolysis[2],pyruvate[3],isfurtheroxidizedtoyieldtheacetylgroup[4]ofacetylcoenzymeA,withlossofitscarboxylgroupasCO2andreleaseofonemoleculeofNADH[5];Thisoxidativedecarboxylation[6]reac

tioniscatalyzedbypyruvatedehydrogenasecomplex[7],aenzymecomplexexistinginmitochondrialmatrix[8],consistingofthreeenzymes — pyruvatedehydrogenase[9]

(E1),dihydrolipoyltransacetylase[10](E2)anddihydrolipoyldehydrogenase[11](E3),

andfivecoenzymesorprostheticgroups[12]—thiaminepyrophosphate[13](TPP),flavinadeninedinucleotide[14](FAD),coenzymeA (CoA),nicotinamideadeninedinucleotide(NAD),andlipoate[15].TheacetylgroupisthenoxidizedcompletelytoCO2bythecitricacidcycle(alsoknownasKrebscycleortricarboxylicacidcycle),thefirstcyclic

pathway[16]wehaveencountered.Tobeginaturnofthecycle,acetylCoAdonatesitsacetylgrouptothefourcarboncompoundoxaloacetate[17]toformthesixcarboncitrate[18],catalyzedbycitratesynthase[19].Citrateisthencatalyzedbycisaconitase[20]toformisocitrate[21],alsoasixcarbonmolecule,whichisdehydrogenated[22]byisocitratedehydrogenase[23]withlossofonemoleculeofCO2andreleaseofonemoleculeof

NADHtoyieldthefivecarboncompoundαketoglutarate[24].αketoglutarateundergoeslossofCO2withthecatalysisofαketoglutaratedehydrogenasecomplexaverysimilarcomplextopyruvatedehydrogenasecomplexandultimatelyyieldsthefourcarboncom

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poundsuccinylCoA[25]andasecondmoleculeofCO2andanothermoleculeofNADH.SuccinylCoAisthenconvertedtosuccinate[26]bysuccinylCoAsynthetase[27]orthiokinase[28],yieldingamoleculeofGTPbysubstratelevelphosphorylation[29].Succinateisthenoxidizedbysuccinatedehydrogenasetofumarate[30]andreleaseonemoleculeofFADH2.Fumarateishydratedtomalate[31]byfumarase[32].Andfinallymalateisdehydrogenatedby malatedehydrogenasetoform oxaloacetate (andone moleculeofNADH),withwhichthecyclebegan;oxaloacetateisthenreadytoreactwithanothermoleculeofacetylCoA.Ineachturnofthecycle,oneacetylgroup(twocarbons)entersasacetylCoAandtwomoleculesofCO2leave,andonemoleculeofoxaloacetateisusedtoformcitrate,butafteraseriesofreactions,theoxaloacetateisregenerated[33].Nonetremovalofoxaloacetateoccurs;onemoleculeofoxaloacetatecantheoreticallybringaboutoxidationofaninfinite[34]numberofacetylgroups,andinfact,oxaloacetateispresentincellsinverylowconcentrations.Fouroftheeightstepsinthisprocessareoxidations,inwhichtheenergyofoxidationisveryefficientlyconservedintheformofthereducedcoenzymesNADHandFADH2[35].

2.Althoughthecitricacidcycleiscentraltoenergyyieldingmetabolism,itsroleisnotlimitedtoenergyconservation.Fourandfivecarbonintermediatesofthecycleserveasprecursors[36]forawidevarietyofproducts.Toreplaceintermediatesremovedforthispurpose,cellsemployanaplerotic(replenishing)reactions[37]toreplenishitsintermediatesespeciallyoxaloacetate.

3.EugeneKennedyandAlbertLehningershowedin1948thatineukaryotestheentiresetofreactionsofthecitricacidcycletakesplaceinmitochondria.Isolatedmitochondriawerefoundtocontainnotonlyalltheenzymesandcoenzymesrequiredforthecitricacidcycle,butalsoalltheenzymesandproteinsnecessaryforthelaststageofrespiration[38]electrontransferandATPsynthesisbyoxidativephosphorylation[39].MitochondriaalsocontaintheenzymesfortheoxidationoffattyacidsandsomeaminoacidstoacetylCoA,andtheoxidativedegradationofotheraminoacidstoαketoglutarate,succinylCoA,oroxaloacetate.

4.Thusinnonphotosyntheticeukaryotes,mitochondrionisthesiteofmostenergyyieldingoxidativereactionsandofthecoupledsynthesisofATP.InphotosyntheticeukaryotesmitochondriaarethemajorsiteofATPproductioninthedark,butindaylightphotophosphorylation[40]inchloroplasts,producemostoftheorganism’sATP.Inmostprokaryotes,theenzymesofthecitricacidcycleareinthecytosol,andtheplasmamembraneplaysarolesimilartothatoftheinnermitochondrialmembraneinATPsynthesis.

 Notes

[1]citricacidcycle[5sitrik5Asid5saikl] 柠檬酸循环

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[2]glycolysis[^lai5kRlisis]糖酵解

[3]pyruvate[pai5ru:veit]丙酮酸

[4]acetylgroup乙酰基

[5]NADH:Reducednicotinamideadeninediphosphate还原性辅酶Ⅰ,还原型烟

(尼克)酰胺腺嘌呤二核苷酸

[6]oxidativedecarboxylation[5Rksideitiv7dikB:7bRks[5leiF[n]n.氧化脱羧

[7] pyruvate dehydrogenase complex[pai5ru:veitdi:5haidr[dV [7neis5kRmpleks]丙 酮 酸 脱 氢 酶 复 合 体

(系)[8]mitochondrialmatrix[7mait[5kCndri[5meitriks]线粒体基质

[9]pyruvatedehydrogenase[pai5ru:veitdi:5haidr[dV[7neis]丙酮酸脱氢酶

[10 ] dihydrolipoyl transacetylase[dai5haidr [lipCil trAnz[5setileis]二 氢 硫 辛 酸 转 乙 酰

基酶

[11]dihydrolipoyldehydrogenase[dai5haidr[lipCildi:5haidr[dV[7neis]二

氢硫辛酸脱氢酶

[12]prostheticgroup[prRs5Wetikgru:p]

n.辅基

[13]thiaminepyrophosphate(TPP)[5Wai[mi:n7pair[u5fRsfeit]n.焦磷

酸硫胺素

[14]flavinadeninedinucleotide(FAD)[5fleivin5Ad[ni:ndai5nju:kl[7taid]黄素

腺嘌呤二核苷酸

[15]lipoate[5li:p[ueit]n.硫辛酸

[16]cyclicpathwayn.循环途径

[17]oxaloacetate[9Rks[l[u5Asiteit]n.草

酰乙酸

[18]citrate[5sitrit]n.柠檬酸

[19]citratesynthase[5sitrit5sinWeis]n.柠檬酸合酶

[20]cisaconitase[sis[5kCniteis]n.顺乌

头酸酶

[21]isocitrate[ais[u5sitrit]n.异柠檬酸

[22]dehydrogenate[di:`haidr[neit]vt.脱

[23]isocitratedehydrogenase[ais[u5sitritdi:

5haidr[dV[7neis]]异柠檬酸脱

氢酶

[24]αketoglutarate[7ki:t[U5glu:tt[reit]

n.α酮戊二酸

[25]succinylCoA[5sQksinilkRnei]n.琥

珀酰辅酶A[26]succinate[5sQksi9neit]n.琥珀酸

[27]succinylCoA synthetase [5sQksinilkRnei5sinWeteis]n.琥珀酰辅

酶A合成酶

[28]thiokinase[7Wai[u5kineis]n.硫激酶

[29 ] substratelevel phosphorylation[5sQbstreitlel5fRsfRrileiF[n]n.底 物

水平磷酸化

[30]fumarate[5fju:m[reit]n.延胡索酸

[31]malate[5mAleit]n.苹果酸

[32]fumarase[5fju:m[reis]n.延胡索酸酶

[33]regenerate[ri5dVen[reit]v.再生

[34]infinite[5infinit]adj.无数的

[35]FADH2:Reducedflavinadeninediphosphonucleotide还 原 型 的 黄 素 腺

嘌呤二核苷酸

[36]precursor[pri5k[:s[]n.前体

[37]anaplerotic[[n[p5ler[utik]reaction回补反应

[38]respiration[7respi55reiF[n]n.呼 吸

作用

[39]oxidativephosphorylation氧化磷酸化

[40]photophosphorylation [7f[ut[ufRsf[reiF[n]光合磷酸化

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犈狊狊犪狔10 犅犾狅狅犱犛狌犫狊狋犻狋狌狋犲[1]

1.Theideaofusingabloodsubstituteinsteadofhumanbloodfortransfusing[2]patientsisnotnew.Inthe17thcentury,SirChristopherWrensuggestedthatale[3],wine,andevenopium[4]couldbeusedassubstitutesforhumanblood.Itwasnotuntil1901thatthemodernageofbloodtransfusionbeganwiththediscoveryofhumanbloodgroup[5]

antigens[6]byKarlLandsteiner.Hecategorized[7]humanbloodintoA,B,andC(laterrenamedO)groups,andayearlatertheABgroupwasaddedtothelist.Thesestudieswerecriticaltounderstandingwhybloodtransfusionshadfailedthusfar.Ottenbergin1913wasthefirsttoapplybloodgroupserology[8]totransfusionpractice.EvenwithOttenberg’sdescriptionofbloodcompatibilitytesting[9],bloodtransfusionswereseverelylimitedbecauseofalackofsuitableanticoagulants[10]andstoragemethods.TheFirstandSecondWorldWarsprecipitated[11]progressonthesetwofronts,atlastallowingbloodtransfusiontobecomeastandardpartofmedicaltreatment.

2.Oneoftheprincipaltasksofbloodistotransportoxygenthroughoutthebodyandthentoreleasetheoxygentotissues,pickingupcarbondioxideinitsstead.Allofthisisaccomplishedbyhemoglobin[12],theoxygencarryingproteincontainedwithinredbloodcells(erythrocytes[13]).Theothercellularconstituentsofbloodarewhitecells,whichareimportantfortheimmuneresponse[14],andcellularfragmentscalledplatelets[15]

thatarecrucialforbloodclottingandwoundhealing.3.Althoughtransfusionofdonorbloodisaroutineandsafeprocedure,thereareseveralreasonsfordevelopingbloodsubstitutes.Humanredbloodcellshaveexacting[16]storagerequirementsdesignedtoprolongclinicaleffectivenessandtoreducetheriskofbacterialcontamination.Thissubstantiallylimitstheavailabilityofbloodatdisastersitesoronthebattlefield.Bloodsubstituteswithlessstringent[17]storagerequirementswouldbevaluableinthesesituations.Inaddition,bloodsubstitutesaremoreamenabletosterilizationtoremoveinfectiouspathogens[18],andtheydonotrequirecrossmatching[19]becausetheydonotharbor[20]bloodgroupantigens.Donorbloodshortagesmakebloodsubstitutesattractivefortheshorttermreplacementoferythrocytesduringsurgery.Inthe1980s,therealizationthatthehumanimmunodeficiencyvirus(HIV)[21]

couldbetransmittedthroughbloodtransfusionprovidedrenewedimpetus[22]forthedevelopmentof“diseasefree”bloodsubstitutes.Beforethedevelopmentofaspecifictestfor HIV,therisk oftransfusionassociatedacquiredimmunodeficiencysyndrome(AIDS[23]wasabout38per100,000transfusedpatients).

4.Researchersinterestedindevelopingbloodsubstitutes(dubbed[24]artificialblood[25])

havepredominantlyconcentratedonmimickingtheoxygencarryingcapacityofhemo

globin.However,inadditiontobeingabletotransportoxygen,anidealbloodsubstitutewouldalso(i)requirenocrossmatchingorcompatibilitytesting,(ii)besuitable

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forlongtermstorage(preferablyatroomtemperature),(iii)beabletosurviveinthecirculationforseveralweeks(theintravascular“dwell”time[26])beforebeingclearedbythekidney,(iv)befreeofsideeffects,(v)befreeofpathogens,and(vi)notonlytransportbutalsoeffectivelydeliveroxygentotissues.Therearetwotypesofbloodsubstitutecurrentlyunderdevelopment:thosederivedfromhemoglobin,calledhemo

globinbasedoxygencarriers(HBOCs)[27],andthosethatuseperfluorocarbonemulsions[28].

5.Thehemoglobininadulterythrocytesisatetramer[29]oftwoαandtwoβpolypeptidechains,eachofwhichisboundtoanironcontainingheme[30]group.Eachhemegroupbindsoneoxygenmolecule.Thisoxygenhemebondresultsinaconformational(shape)

changeinthehemoglobinmolecule,whichinturnprogressivelyincreasestheaffinity[31]

ofhemoglobinforadditionaloxygenmolecules.Thus,asmallchangeinoxygenpartial

pressure[32]resultsinalargechangeintheamountofoxygenboundorreleasedbyhemoglobin.Anumberofadditionalfactors,suchastemperatureandpH,canaltertheoxygenhemoglobindissociationcurve.Similarly,2,3diphosphoglycerate (2,3DPG)[33],aproductoftheredbloodcellglycolyticpathwayandpresentinnormalhumanerythrocytes,alsodirectlyaffectsthebindingofoxygentohemoglobin.Astheconcentrationof2,3DPGrises,theoxygenhemoglobindissociationcurve“shiftstotheright,”therebyallowingthereleaseofoxygentotissuesathigherthannormaloxygen

partialpressures.6.Acellfreesolutionofhemoglobincanbeusedasabloodsubstitutebecausehemoglobinmaintainsitsabilitytotransportoxygenoutsideoftheredbloodcell.OneadvantageofHBOCsisthatcompatibilitytestingisnotrequired.Incontrast,transfusionofdonorbloodrequirescarefulcrossmatchingtoavoidtheconsequencesofahemolytic[34]transfusionreactionintherecipient,thecauseofasmallbutsignificanttransfusionassociatedmorbidity[35]andmortality[36].Anotheradvantageofcellfreehemoglobinisthatitcanbesterilizedbyultrafiltration[37]andlowheattoinactivate[38]infectiousagents,astrategythatisnotpossiblewithredbloodcells.

7.Earlyattemptstodevelopbloodsubstitutesinthe1970sconcentratedoncellfreesolutionsofhumanhemoglobin.ButproblemswiththeseHBOCsincludedunacceptablyshortsurvivaltimesinthecirculation,anabnormallyhighoxygenaffinity,andclinicalsideeffectssuchasmalaise[39],abdominalpain[40],hemoglobinuria[41],andrenaltoxicity[42].IfHBOCsaretobecomeclinicallyeffectivebloodsubstitutes,twoprincipalchallengesmustbeovercome:theirshortintravasculardwelltimes,andtheirreducedabilitytooxygenatetissuesrelativetonormalhemoglobin.

8.Thefirstchallengeistopreventtherapidbreakdownandeliminationbythekidneyofhemoglobinmoleculesthatarenolongerwithintheprotectiveenvironmentoftheredbloodcell.Intracellularhemoglobinhasthesamelifespanastheerythrocyte,about120days,butinsolutionthehemoglobintetramerreadilydissociatesintomonomersanddimmers[43]thatarequicklyeliminatedbythekidneys.Thedissociationofoxygen

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fromintracellularhemoglobinismodifiedby2,3DPG,resultinginanormalP50value(theoxygenpartialpressureatwhichhemoglobinis50%saturated)ofabout27mmHgforhumanblood.Inhemoglobinsolutions,thelackof2,3DPGcausesa“leftshift”intheoxygendissociationcurve,thatis,anincreaseintheaffinityofhemoglobinforoxy

gen.AlthoughthisincreasedaffinitydoesnotlimittheabilityofHBOCstotransportoxygen,itdoesseriouslylimittheirabilityto“unload”ordeliveroxygentotissues.

9.Thesetwochallengeshavebeenaddressed[44]bychemicallymodifyingcellfreehemoglobin.InthefirstclassofmodifiedHBOCs,specificchemicalcrosslinksareestablishedbetweenhemoglobinpolypeptidechainstopreventthedissociationofthehemoglobintetramer,thusretardingrenalelimination.Treatmentwith3,5dibromosalicylfumarate[45]resultsinastrongcovalentbondthatmaintainstheintegrityofthehemoglobintetramer.Thisresultsinaprolongedintravasculardwelltimeofupto12hours;bycontrast,untreatedcellfreehemoglobiniseliminatedbythekidneyinlessthan6hours.Alternatively,hemoglobincanbetreated withbifunctionalcrosslinkinga

gents[46],suchasraffinose[47]orglutaraldehyde[48],thattargetspecificaminogroupsandpolymerizethehemoglobinmolecule.Thesereagentsproducepolyhemoglobin[49],

composedoffourorfivehemoglobinmolecules,whichvariesinmolecularsizeandconfiguration[50]andhasintravasculardwelltimesofupto24hours.Finally,hemoglobincanbeconjugatedtoavarietyoflargermoleculessuchasdextran[51],polyethyleneglycol[52],orpolyoxyethylene[53],retardingtherateatwhichitisclearedfromthecirculation.Inthisinstance,theintravasculardwelltimecanbeextendedto48hours.NewHBOCsunderdevelopmentincludepolyhemoglobinlinkedtoantioxidant[54]enzymessuchassuperoxidedismutase[55]andcatalaseinanefforttominimizeischemiareperfusioninjury[56].Inaddition,somegroupsaretryingtopackagehumanhemoglobininartificialredbloodcellsmadefrombiodegradablepolymernanocapsules[57]orlipidvesicles[58].

10.Thereareatleastthreemodifiedhemoglobinproductscurrentlyinadvancedclinicaltrials.NorthfieldLaboratorieshasdevelopedPolyheme,apolymerizedhumanhemoglobin

product.Biopurehaspreparedpolymerizedhemoglobinfrombovine[59]redbloodcells(Hemopure),whichhasreceivedapprovalforuseasabloodsubstituteintheRepublicofSouthAfricaandisnowawaitingFDAreviewofaphaseIIIclinicaltrialintheUnitedStates.Finally,HemosolhasdevelopedHemolink,apartiallypolymerizedhumanhemoglobinproductthatisalsounderFDA[60]review.

11.ThereareseveralproblemswithHBOCsthatmustbeovercome.Thefirstisthesourceofthehemoglobinusedinthebloodsubstitute.Anobviouscandidateishumanhemo

globinderivedfromoutdateddonorblood(redbloodcellsthathaveexceededtheap

provedstorageperiod),butthelimitedsupplyofhumanbloodhascompoundeddifficultiesindevelopingahumanderived HBOC.A morereadilyavailable(andcheaper)

sourceofhemoglobinisbovineblood.Bovinehemoglobindoesnothave2,3DPG,resultinginaP50ofabout30mmHgbothinsideandoutsidetheredbloodcell(similarto

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thatoftheintracellularnativehumanhemoglobin).Inaddition,oncestrippedofallotherproteins,bovinehemoglobinisnotrecognizedbythehumanimmunesystemasforeign.However,onepotentialobstacletotheacceptanceofabovinederivedHBOCisthefearthatitcouldharbortheprion[61]pathogenthatcausesbovinespongiformencephalopathy[62].Geneticallyengineeringbacteriatoproducearecombinantsourceofhumanhemoglobinwouldeliminatetheconcernsaboutdiseasetransmissionassociatedwithhemoglobinderivedfromhumansoranimals.Ofcourse,theproblemwiththisapproachisthecostofscalingupoperationssufficientlytoyieldthelargevolumesofhemoglobinrequiredforroutinetransfusions。

 Notes

[1]bloodsubstitute[blQd5sQbstitjuit]

n.血液替代品

[2]transfuse[trAns5fju:z]vt.输血

[3]ale[eil]n.淡色啤酒(较一般啤酒含更

多的酒精)[4]opium[5[upj[m]n.鸦片

[5]bloodgroup[blQdgru:p]n.血型

[6]antigen[5AntidV[n]n.抗原

[7]categorize[5kAtig[raiz]v.加 以 类

别,分类

[8]serology[si[5rl[dVi]n.血清学

[9]bloodcompatibility[k[m7pAti5biliti]

testing血液兼容性试验

[10]anticoagulant[5Antik[U5Agjul[nt]

n.抗凝血剂

[11]precipitate[pri5sipiteit]vt.加 速,促

使,促成

[12]hemoglobin[7hi:m[u5gl[ubin]n.血

红蛋白

[13]erythrocyte[i5riWr[usait]n.红细胞

[14]immuneresponse[i5mju:nris5pRns]

n.免疫反应

[15]platelet[5pleitlit]n.血小板

[16]exacting[ig5zAktiN]adj.苛 求 的,

严格的,吃力的,需付出极大耐心

[17]stringent[5strindV[nt]adj.严厉的,

迫切的,银根紧的

[18]pathogen[5pAW[dV[n]n.病 菌,病

原体

[19]crossmatching交叉匹配

[20]harbor[5hB:b[]vt.为……提供地方、

住房或栖息地

[21]humanimmunodeficiencyvirus(HIV)[5hju:m[n7imjun[di5fiF[nsi5vai[r[s]n.人 类 免 疫 缺 陷 病 毒(艾 滋 病 病

原)[22]impetus[5impit[s]n.推动力,促进

[23]acquiredimmunodeficiencysyndrome(Aids)[[5kwai[d7imjun[di5fiF[nsi5sindr[um]n.获 得 性 免 疫 缺 陷 综 合

症(艾滋病)[24]dub[dQb]vt.[电 影]配 音,给……起

(绰号)[25]artificialblood[7B:ti5fiF[lblQd]n.

人造血液

[26]intravascular[7intr[5vAskjul[]“dwell”time血管内停留时间

[27]hemoglobinbasedoxygencarriers(HBOCs)基于血红蛋白的氧载体

[28]perfluorocarbonemulsion[p[7flu:[r[5kB:b[ni5mQlF[n]全 氟 碳 化 合 物

乳剂

[29]tetramer[5tetr[m[]n.四聚体

[30]heme[hi:m]n.血红素

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[31]affinity[[5finiti]n.亲和力

[32]partialpressure分压

[33]2,3diphosphoglycerate(2,3DPG)[dai9fRsf[u5glis[reit]2,3二 磷 酸 甘

油酸

[34]hemolytictransfusion[hi:mR5litiktrAns5fjuV[n]reaction溶血性输血反

[35]morbidity[mR:5biditi]n.发病率

[36]mortality[mR:5tAliti]n.死亡率

[37]ultrafiltration[7Qltr[fil5treiF[n]n.超滤(作用)

[38]inactivate[in5Akiveit]vt.使钝化,减

除……的活性;破坏(细 菌 等 的)传 染

[39]malaise[mA5leiz]n.[法]不 适;小

病,精神欠爽

[40]abdominal[Ab5dRminl]pain腹痛

[41]hemoglobinuria[7hi:m[7gl[ubi5nju[ri[]n.血红蛋白尿

[42]renaltoxicity[5ri:nltRk5sisiti]n.肾

脏毒性

[43]dimer[5daim[]n.二聚体

[44]address[[5dres]vt.处理,从事,忙于

[45]3,5dibromosalicylfumarate[5daibr[um[u5sAlisil5fju:m[reit]3,5二 溴 水 杨

酰延胡索酸

[46]bifunctional[7bai5fQnkF[nl]cross-linkingagent双功能交联剂

[47]raffinose[5rAfin[us]n.棉子糖

[48]glutaraldehyde[7glu:t[5Aldi9haid]

n.戊二醛

[49]polyhemoglobin [pRli7hi:m [u5gl[ubin]n.多聚血红蛋白

[50]configuration[k[n7figju5reiF[n]n.构型

[51]dextran[5dekstrEn]n.葡聚糖

[52 ] polyethylene glycol (PEG )[7pRli5eWili:n5glaikRl]n.聚乙二醇

[53]polyoxyethylene[7pRli5[uksieWili:n]

n.聚氧乙烯

[54]antioxidant[5Anti5Cksid[nt]adj.抗

氧化的

[55]superoxidedismutase(SOD)[7sjU:p[5Rksaiddismju:teis]n.超氧物歧化

[56]ischemiareperfusioninjuryn.缺血再

灌注损伤

[57]biodegradablepolymernanocapsule[nAn[u5kApsjul]n.生 物 可 降 解 的 多 聚 物

微胶囊

[58]lipidvesicle[5lipid5vesikl]n.脂质小

[59]FDAn.(美 国)食 品 及 药 物 管 理 局

(FoodandDrugAdministration)[60]bovine[5b[uvain]adj.牛的,[61]prion[prai[n]n.朊病毒(感染性蛋白

质):极 微 小 的 蛋 白 质 微 粒,类 似 于 病

毒,但不含核酸,被认为是绵羊痒病和

其他的一 些 神 经 系 统 变 性 疾 病(如 疯

牛病)的传染介质。[62]bovinespongiformencephalopathy[5b

[uvain5spQndVifR:m en9sf[5lRp[Wi]n.牛绵状脑病

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犝犖犐犜04 犅犗犜犃犖犢犃犖犇犘犔犃犖犜犘犎犢犛犐犗犔犗犌犢

犈狊狊犪狔11 犛狋狅犿犪狋犪犾犃狀犪狋狅犿狔

1.Stomata[1]comeinconsiderablevariety.Thewaxycuticle[2]onleafsurfacesrestrictsdiffusion[3],somostwatervaporandothergasesmustpassthroughtheopeningsbetweentheguardcells.Someanatomists[4]insistthatthetermstomarefersonlytothisopening,butothersapplythistermtotheentirestomatalapparatus[5],whichincludestheguardcells.Theopeningisthencalledthestomatalpore[6].Adjacenttoeachguardcellareusuallyonetoseveralothermodifiedepidermalcellscalledaccessoryorsubsidiarycells[7],thenumberandarrangementdependingontheplantfamily,althoughdifferenttypescanoccuronasingleleaf.Waterevaporatesinsidetheleaffromcellwallsofthepalisadeparenchyma[8]andspongyparenchyma[9],collectivelythemesophyll[10],

intotheintercellularspaces,whicharecontinuouswiththeoutsideairwhenthestomataareopen.Carbondioxidefollowsthereversediffusionpathintotheleaf.Manyofthecellwallsofmesophyllcellsareexposedtotheinternalleafatmosphere,althoughthisisseldomevidentforpalisadecellsindrawingsandphotomicrographsofleafcrosssections.Thisarrangementbecomesmuchmoreapparentinsectionsthroughthepalisade,

paralleltotheleafsurface,andisalsostrikinglyapparentinscanningelectronmicro

graphs.Thereismuchvariabilityintheanatomyofleaves.AspecialkindofphotosynthesiscalledC4photosynthesisisespeciallyprevalentintropicalgrassessuchasmaize.LeaveswithC4photosynthesishaveaspecialanatomycalledKranzanatomy[11](fromtheGermanwordforwreath)inwhichthelayerofcellsaroundthevascularbundles[12]

isespeciallyprominent,withalargenumberofchloroplasts.Mostplantshavebundlesheathcells[13],buttheyareeasytooverlookinspeciesthatdonothaveKranzanatomy.ItplaysaspecialroleinC4photosynthesis.

2.Stomatasometimesoccuronlyonthelowersurfacesofleavesbutoftenarefoundonbothsurfaces,oftenwithmoreonthebottoms.Waterlilypadshavestomataonlyontop,andsubmergedplantshavenoneatall.Grassesusuallyhaveaboutequalnumbersoneachside.Sometimes,asintheoleander[14]orpine,thestomataoccurinastomatalcrypt[15].Suchsunkenstomataareapparentlyanadaptationthatreducestranspiration.

3.Typicalstomataofdicots[16]consistoftwokidneyshapedguardcells[17];grassandsedgeguardcellstendtobemoreelongate(dumbbellshaped[18]).Guardcellscontainafewchloroplasts,whereastheirneighboringepidermalcellsusuallydonot(exceptin

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fernsandafewaquaticangiosperms[19]).Typically,thereareno(orincomplete)plasmodesmata[20]connectingtheprotoplastsofguardcellsandaccessorycells,buttheremaybeplasmodematabetweenguardcellsandthemesophyllcellsbelow.

4.Typically,eachsquaremillimeterofleafsurfacehasabout100stomata,butthenumbercanbetentimesthat,withamaximumsofarrecordedof2,230.RecentstudiessuggestthatstomataldensitiesaresensitivetoCO2concentration,withfewerstomataperunitareaasCO2increases.Thiswasshownbybothlaboratorystudiesandbystomatacountsofagivenspeciesasafunctionofincreasingelevation(CO2partialpressuredecreasesalongwiththeothergasesintheatmospherewithincreasingelevation).Itwasalsofoundbyexaminingherbarium[21]specimens[22]thatstomataldensitieshavedecreasedby40percentoverthepasttwocenturiesasCO2intheatmospherehasincreasedfrom280toover350μmolmol

-1

 Notes

[1]stomata[5st[umeit[]n.气孔 (pl.ofstoma)

[2]cuticle[5kju:tikl]n.角质层

[3]diffusion[di5fju:V[n]n.扩散

[4]anatomist[[5nAt[mist]n.解剖学家

[5]stomatalapparatus气孔器

[6]stomatalpore气孔

[7]accessoryorsubsidiarycells护卫细胞

[8]palisadeparenchyma [7pAli5seidp[5reNkim[]n.栅栏薄壁组织

[9]spongy parenchyma [5spQndVi p[5reNkim[]n.海绵薄壁组织

[10]mesophyll[5mes[fil]n.叶肉

[11]Kranzanatomy花环状结构

[12]vascularbundle[5vAskjunl[5bQndl]

n.微管束

[13]bundlesheathcell微管束鞘细胞

[14]oleander[9[uli5And[]n.夹竹桃

[15]stomatalcrypt[kript]n.气孔隐囊

[16]dicot[5daikRt]n.双子叶植物

[17]kidneyshapedguardcell肾 形 保 卫 细

[18]dumbbellshaped 哑 铃 性 的(保 卫 细

胞)[19]angiosperm [5AndVi[u7sp[:m]n.被

子植物

[20]plasmodesmata[9plAzm[u5dezmeit[]

n.胞间连丝(pl.ofplasmodesma)[21]herbarium[h[:5bZ[ri[m]n.植物标本

室,腊叶集,干燥标本集

[22]specimen[5spesim[n]n.标本

犈狊狊犪狔12 犜犺犲犘犪狉犪犱狅狓狅犳犘狅狉犲狊

1.Natureoftenprovestobemorecomplexthanweexpect.Supposewecomparetheevaporationratefromabeaker[1]ofwaterandfromanidenticalbeakerthatishalfcovered,

saywithmetalstrips[2].Wewouldexpectevaporationfromthesecondbeakertobeabouthalfofthatfromthefirst.Nowlet’scoverallbutabout1percentofthesecond

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beaker.Westilluseathinpieceoffoil[3]withsmallholesmakingupabout1percentofthetotalarea.Willwemeasureabout1percentasmuchevaporation?Notiftheholeshaveaboutthesamesizeandspacingasstomatafoundintheepidermis[4]ofaleaf.Wewillinfactmeasureabouthalfasmuchevaporationasfromtheopensurface.

2.Howcanthisbe?Whyisn’tevaporationdirectlyproportionaltosurfacearea?Itcertainlyseemsparadoxical[5]thatstomatalopeningsontheleafmakeuponlyabout1percentofthesurfacearea,whereastheleafsometimestranspires[6]halfasmuchwateraswouldevaporatefromanequivalentareaofwetfilterpaper.Weresolvethisapparentparadoxbyrealizingthatevaporationisadiffusionprocessfromwatersurfacetoatmosphere.Simplystated,diffusionisproportionaltothedrivingforceandtheconductivity[7].Inourexample,thedrivingforceisthesameforbothbeakers:thedifferenceinvaporpressure(ordensity)betweenthewatersurface(wheretheatmosphereissaturatedwithvapor)andtheatmospheresomedistanceaway(whereitmustbebelowsaturationifevaporationistooccur).

3.Thedifferentevaporationratesdependondifferentconductivitiestodiffusion.Partoftheconductivityisafunctionofthearea,andthisvalueismuchlowerabovethebeakercoveredwithporousfoil,whichiswhatweexpected.Buttheotherpartoftheconductivitydependsonthedistanceintheatmospherethroughwhichwatermoleculesmustdiffusebeforetheirconcentrationreachesthatoftheatmosphereasawhole.Theshorterthedistanceis,thehighertheconductivity.Thisdistancecanbecalledtheboundarylayer[8],anditismuchshorterabovetheporesinthefoilthanabovethefreewatersurface.Moleculesevaporatingfromthefreewaterwillbepartofarelativelydensecolumnofmoleculesextendingsomedistanceabovethesurface,whereasmoleculesdiffusingthroughaporecangoinanydirectionwithinanimaginaryhemisphere,theconcentrationdropsrapidlywithdistancefromthepore,whichistosaythattheconcentrationgradient[9]isverysteepbecausetheboundarylayerisverythin.Ofcourseifporesareclosertogetherthanthethicknessoftheirboundarylayers,thesehemispheresoverlapandmergeintoaboundarylayer.

4.Manyempiricalstudiesweremadeseveraldecadesagotodeterminetheeffectsofporesize,shape,anddistributionondiffusionrates.Stomataoftypicalplantsprovedtobenearlyoptimalformaximumgasorvapordiffusion.Thus,plantsareideallyadaptedforCO2absorptionfromtheatmospherebutalsoforlossofwaterbytranspiration.Thestomatacanclose,however,andinmostplantstheyareadaptedtoclosewhenphotosynthesisandCO2absorptionstop(forexample,indarkness).

 Notes

[1]beaker[5bi:k[]n.烧杯

[2]metalstripsn.铁带,钢带

[3]foil[fRil]n.锡箔纸

[4]epidermis[7epi5d[:mis]n.表皮

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[5]paradoxical[7pAr[5dRksiik[l]adj.奇

怪的

[6]transpire[trAns5pai[]v.蒸 发,蒸 腾;泄漏机密

[7]conductivity[7kRndQktiviti]n.传 导

[8]boundarylayer界面

[9]concentrationgradient[7kRnsen5treiF[n5greidi[nt]n.浓度梯度

犈狊狊犪狔13 犗狊犿狅狊犻狊

1.Itisaneverydayexperiencetoturnonawaterfaucet[1]orflushatoilet[2].Thusweare

perfectlyfamiliarwithwatermovementasabulkflowphenomenon[3]—ourplumbingsystems[4]seetothat!Butintheworldaroundus,vastquantitiesofwateraremoving,

usuallyinvisibly,bydiffusion.2.Ittakessomementalefforttovisualizethesemoreunfamiliaraspectsoftherealworld.Withourmind’seye(thereisnootherway)wemustseethosewatermolecules,flyingandbouncingbillionsoftimeseachsecondinthevaporstate,holdingeachotherintheliquidstatewiththeirhydrogenbonding—positivesideofonetonegativesideofanother—evenwhiletheirkinetic[5]motionscausesometoseparate.Wemustsomehow

conceptualizetheentropy[6],freeenergy,andchemicalpotentials[7]andhowthese

propertiescandrivethemoleculestodiffusedownagradient.Wemustrealizethat

pressureincreasesfreeenergiesandchemicalpotentials,whereassoluteparticlesandmatricsurfacesdecreasethem.

3.Withthesemodelsinmind,wearereadytoextendourconceptstothecellsofplants.Wearereadytodiscussosmosisandrelatedmatters.

4.Adevicethatmeasuresosmosisisanosmometer[8].Thisisusuallyalaboratorydevice,

butalivingcellmaybethoughtofasanosmoticsystem.Inbothcases,twothingsareusuallypresent:First,twoormorevolumesofsolutionsorpurewaterareisolatedfromeachotherbyamembranethatrestrictsthemovementofsoluteparticlesmorethanitrestrictsthemovementofsolventmolecules.Second,thereisusuallysomemeansofallowingpressuretobuildupinatleastoneofthevolumes.Inthelaboratoryosmometer,pressuretypicallybuilduphydrostaticallybyraisingthesolutioninthetubea

gainstgravity,butothermeanscanbeused,suchasavolumedetector(forexample,alightbeamandphotocell[9])thatcanincreasepressureinthesystem(forexample,withapiston[10])assoonasthevolumeofliquidbeginstoexpandbythefirstsmallincrement.Inthecell,therigidityoftheplantcellwallisresponsiblefortheincreasein

pressure.5.Itisimportanttoemphasizethestructuraldifferencesbetweenthecellmembraneandthecellwall.Themembraneallowswatermoleculestopassmorerapidlythansolute

particles;theprimarycellwallisusuallyhighlypermeabletoboth.Itistheplantcell

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membranethatmakesosmosispossible,butitisthecellwallthatprovidestherigiditytoallowabuildupinpressure.Animalcellsdonothavewalls,sowhenpressuresbuildupinthem,theyoftenburst,ashappenswhenredbloodcellsareplacesinwater.Tur

gidcellsprovidemuchoftherigidityofnonwoodyplantparts.6.Consideratfirstaperfectosmometer.Insuchadevice,themembraneissemipermea

ble[11],allowingreadypassageofsolvent(water),butnopassageofsolute,andthesolutionissostronglyconfinedthatmovementofwaterintotheosmometercausesnosignificantincreaseinsolutionvolume.Anearlyperfectosmometercanbeconstructedinthelab,butacellisneverperfectosmoticsystem.

7.Restrictingthediffusionofsoluteparticlescomparedwithsolventmoleculescanresultintheestablishmentofawaterpotentialgradient[12].Ifthereispurewaterononesideofthemembraneandasolutionontheotherside(typicallyinsidethelaboratoryosmometerorthecell),thenthewaterpotentialofthesolutionwillbelowerthanthatofthepurewater.Byconvention[13],waterpotentialofpurewateratatmosphericpressureandatthesametemperatureassolutionbeingconsideredissetequaltozero,sothewaterpotentialofanaqueoussolutionatatmosphericpressurewillbesomenegativenumber(lessthanzero).Hence,watermoleculeswilldiffusefromthehigherwaterpotentialontheoutsidetothelowerwaterpotentialinthecellsolution;thatis,waterwilldiffuse“down”awaterpotentialgradientintothesolution.Theresultwillbeabuildupofpressurewithinthesystem,eitheraraiseofliquidinthetubeofthelaboratoryosmometerorofpressureuponthecellwall.Increasingpressureraisesthewater

potential,sothewaterpotentialwithintheosmoticsystemwillbegintoincreasetowardzero.

8.Thesituationisanalogoustothescaleofathermometer,butinthiscasewearedealingalmostexclusivelywithvaluesbelowzero.Addingsolutedecreasesthewaterpotentialtosomelevelbelowzero,andaddingpressureraisesthistowardzero.

9.Ifpurewaterisononesideofthemembrane,pressureontheothersidewillincreaseuntilthewaterpotentialofthesolutionisequaltozero,thatis,equaltothewaterpotentialofthepurewaterontheotherside.Whenwaterpotential(ψ)areequalonbothsides,thewaterpotentialdifference(Δψ)betweenthetwosidesofthemembraneiszero,andequilibriumhasbeenachieved(Δψ=ψ1-ψ2=0).

10.Ifononesideofthemembranethereisasolutionandontheothersideanothersolutionofdifferentconcentration,osmosiswillstilloccur.Themoreconcentratedsolutionwillhavethelower(morenegative)waterpotential,sowaterwilldiffuseintoitfromtheothersolutionuntilitspressurebuildsup,ifitisconfinedsothatthatispossible,tothe

pointatwhichitswaterpotentialequalsthatofthelessconcentratedsolution.Ifdiffusionoccursintoasolutionthatisnotconfined,itwillcontinueuntilmoreconcentratedsolutionhasbeendilutedtothepointatwhichitswaterpotentialequalsthatofthesolutionontheothersideofthemembrane.Ineithercase,bothsolutionswillhaveawater

potentialofsomenegativebutequalvalue,andequilibriumwillhavebeenreached.

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11.Actually,theprocessiscompletelygeneral.Therecouldbepressureonbothsolutions,

orthesolutionoutsidetheosmometermightbemoreconcentrated(waterwouldmoveout),butwhenequilibriumisachieved,waterpotentialwillbeequalinallpartsofthesystem(ψ1=ψ2=ψi,andhence,Δψ=0).Thisisnottosaythatψ=0inallpartsofthesystem;twosolutionsinequilibriumwitheachotheracrossamembranewouldbothhavethesamewaterpotentialofsomenegativenumber.

 Notes

[1]waterfaucet[5fC:sit]n.水龙头

[2]flush[flQF]atoilet冲厕所

[3]bulkflowphenomenon[fi5nCmin[n]集流现象

[4]plumbing[5plQmiN]system 排 水 管

道系统

[5]kinetic[kai5netik]adj.动力学的

[6]entropy[5entr[pi]n.熵

[7]chemicalpotential化学势

[8]osmometer[Cz5mRmit[]n.渗透计

[9]photocell[5f[ut[sel]n.光电池

[10]piston[5pist[n]n.活塞

[11]semipermeable [5semi5p[:mj[bl]

adj.半渗透性的

[12]waterpotentialgradient水势梯度

[13]convention[k[n5venF[n]n.惯例

犈狊狊犪狔14 犘狉犻狀犮犻狆犾犲狊狅犳犘犺狅狋狅狊狔狀狋犺犲狋犻犮犈狀犲狉犵狔犜狉犪狀狊犳狅狉犿犪狋犻狅狀

1.Theenergythatdrivesphotosynthesisoriginatesinthecenterofthesun,wheremassisconvertedtoheatbythefusionofhydrogen.Overtime,theheatenergyreachesthesun’ssurface,wheresomeofitisconvertedtolightbyblackbody[1]radiationthatrea

chestheearth.Asmallfractionofthevisiblelightincidenton[2]theearthisabsorbedbyplants.Throughaseriesofenergytransducingreactions,photosyntheticorganismsareabletotransformlightenergyintochemicalfreeenergyinastableformthatcanlastforhundredsofmillionsofyears(e.g.fossilfuels).Asimplifiedscheme[3]describinghowenergyistransformedinthephotosyntheticprocessispresentedinthissection.Thefocusisonthestructuralandfunctionalfeaturesessentialfortheenergytransformingreactions.Forclarity,mechanisticandstructuraldetailsareomitted.A morehighlyresolveddescriptionofoxygenicandanoxygenic[4]photosynthesisisgivenintheremainingsections.

2.Thephotosyntheticprocessinplantsandalgaeoccursinsmallorganellesknownaschloroplaststhatarelocatedinsidecells.Themoreprimitivephotosyntheticorganisms,forexampleoxygeniccyanobacteria,prochlorophytes[5]andanoxygenicphotosyntheticbacteria,lackorganelles.Thephotosyntheticreactionsaretraditionallydividedintotwostages—the“lightreactions[6],”whichconsistofelectronandprotontransferreac

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tionsandthe“darkreactions[7],”whichconsistofthebiosynthesisofcarbohydratesfromCO2.Thelightreactionsoccurinacomplexmembranesystem(thephotosyntheticmembrane)thatismadeupofproteincomplexes,electroncarriers,andlipidmolecules.Thephotosyntheticmembraneissurroundedbywaterandcanbethoughtofasatwodimensionalsurfacethatdefinesaclosedspace,withaninnerandouterwater

phase.Amoleculeorionmustpassthroughthephotosyntheticmembranetogofromtheinnerspacetotheouterspace.Theproteincomplexesembedded[8]inthephotosyntheticmembranehaveauniqueorientation[9]withrespecttotheinnerandouterphase.Theasymmetrical[10]arrangementoftheproteincomplexesallowssomeoftheenergyreleasedduringelectrontransporttocreateanelectrochemicalgradient[11]ofprotonsacrossthephotosyntheticmembrane.

3.Photosyntheticelectrontransportconsistsofaseriesofindividualelectrontransferstepsfromoneelectroncarriertoanother.Theelectroncarriersaremetalioncomplexesandaromaticgroups.Themetalioncomplexesandmostofthearomaticgroupsareboundwithinproteins.Mostoftheproteinsinvolvedinphotosyntheticelectrontransportarecomposedofnumerouspolypeptidechainsthatlace[12]throughthemembrane,providingascaffold[13]formetalionsandaromaticgroups.Anelectronentersaproteincomplexataspecificsite,istransferredwithintheproteinfromonecarriertoanother,andexitstheproteinatadifferentsite.Theproteincontrolsthepathwayofelectronsbetweenthecarriersbydeterminingthelocationandenvironmentofthemetalioncomplexesandaromaticgroups.Bysettingthedistancebetweenelectroncarriersandcontrollingtheelectronicenvironmentsurroundingametalioncomplexoraromaticgroup,theproteincontrolspairwiseelectrontransferreactions.Betweenproteins,electrontransferiscontrolledbydistanceandfreeenergy,andbytheprobabilitythatthetwoproteinsareinclosecontact.Proteinassociationiscontrolledbyanumberoffactors,includingthestructureofthetwoproteins,theirsurfaceelectricalandchemicalpropertiesandthe

probabilitythattheycollidewithoneanother.Notallelectroncarriersareboundto

proteins.Thereducedformsofplastoquinone[14]orubiquinone[15]andnicotinamideadeninedinucleotidephosphate(NADPH)orNADHactasmobileelectroncarriersoperatingbetweenproteincomplexes.Forelectrontransfertooccur,thesesmallmoleculesmustbindtospecialpocketsintheproteinsknownasbindingsites.Thebindingsitesarehighlyspecificandareacriticalfactorincontrollingtherateandpathwayofelectrontransfer.

4.Thelightreactionsconvertenergyintoseveralforms.Thefirststepistheconversionofaphoton[16]toanexcitedelectronicstateofanantennapigment[17]moleculelocatedintheantennasystem[18].Theantennasystemconsistsofhundredsofpigmentmolecules(mainlychlorophyllorbacteriochlorophyll[19]andcarotenoids[20])thatareanchored[21]

toproteinswithinthephotosyntheticmembraneandserveaspecializedproteincomplexknownasareactioncenter[22].Theelectronicexcitedstateistransferredovertheantennamoleculesasanexciton[23].Someexcitonsareconvertedbackintophotonsandemit

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tedasfluorescence[24],someareconvertedtoheat,andsomearetrappedbyareactioncenterprotein.Excitonstrappedbyareactioncenterprovidetheenergyfortheprimaryphotochemicalreaction[25]ofphotosynthesis—thetransferofanelectronfromadonormoleculetoanacceptormolecule.Boththedonorandacceptormoleculesareattachedtothereactioncenterproteincomplex.Onceprimarychargeseparation[26]occurs,thesubsequentelectrontransferreactionsareenergetically[27]downhill.

5.Inoxygenicphotosyntheticorganisms[28],twodifferentreactioncenters,knownasphotosystem[29]IIandphotosystemI,workconcurrently[30]butinseries.InthelightphotosystemIIfeedselectronstophotosystemI.TheelectronsaretransferredfromphotosystemIItothephotosystemIbyintermediate[31]carriers.ThenetreactionisthetransferofelectronsfromawatermoleculetoNADP+,producingthereducedform,

NADPH.Inthephotosyntheticprocess,muchoftheenergyinitiallyprovidedbylightenergyisstoredasredoxfreeenergy[32](aformofchemicalfreeenergy)inNADPH,tobeusedlaterinthereductionofcarbon.Inaddition,theelectrontransferreactionsconcentrateprotonsinsidethemembranevesicleandcreateanelectricfieldacrossthephotosyntheticmembrane.Inthisprocesstheelectrontransferreactionsconvertredoxfreeenergyintoanelectrochemicalpotentialofprotons.Theenergystoredintheprotonelectrochemicalpotentialisusedbyamembraneboundproteincomplex (ATPSynthase[33])tocovalentlyattachaphosphategrouptoadenosinediphosphate(ADP),

formingadenosinetriphosphate(ATP).ProtonspassthroughtheATPSynthaseproteincomplexthattransformselectrochemicalfreeenergyintoatypeofchemicalfreeenergyknownasphosphategrouptransferpotential[34](orahighenergyphosphatebond).TheenergystoredinATPcanbetransferredtoanothermoleculebytransferringthephosphategroup.TheneteffectofthelightreactionsistoconvertradiantenergyintoredoxfreeenergyintheformofNADPHandphosphategrouptransferenergyintheformofATP.Inthelightreactions,thetransferofasingleelectronfromwatertoNADP+involvesabout30metalionsand7aromaticgroups.Themetalionsinclude19Fe,5Mg,4Mn,and1Cu.Thearomaticsincludequinones[35],pheophytin[36],

NADPH,tyrosine[37]andaflavoprotein[38].TheNADPHandATPformedbythelightreactionsprovidetheenergyforthedarkreactionsofphotosynthesis,knownastheCalvincycle[39]orthephotosyntheticcarbonreductioncycle[40].Thereductionofatmos

phericCO2tocarbohydrateoccursintheaqueousphaseofthechloroplastandinvolvesaseriesofenzymaticreactions.ThefirststepiscatalyzedbytheproteinRubisco(Dribulose1,5bisphosphatecarboxylase/oxygenase)[41]whichattachCO2toafivecarboncompound.Thereactionproducestwomoleculesofathreecarboncompound.Subse

quentbiochemicalreactionsinvolveseveralenzymesthatreducecarbonbyhydrogentransferandrearrangethecarboncompoundstosynthesizecarbohydrates.Thecarbonreductioncycleinvolvesthetransferofchemicalbondenergyandrearrangementofchemicalbonds.

6.Inanoxygenicphotosyntheticorganisms[42],waterisnotusedastheelectrondonor.E

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lectronflowiscyclicandisdrivenbyasinglephotosystem,producingaprotonelectrochemicalgradientthatisusedtoprovideenergyforthereductionofNAD+byanexternalHatomoredonor(e.g.H2Soranorganicacid)inaprocessknownas“reverseelectronflow[43]”.FixationofCO2occursviadifferentpathwaysindifferentorganisms.

 Notes

[1]blackbody(光、热)黑体

[2]incident[5insidd[nt]adj.[物]入 射

[3]scheme[ski:m]n.方案,图解

[4]anoxygenic[An7Rksi5dVenik]adj.非放氧的

[5]prochlorophyte[pr[u5klR:r[7fait]n.前绿色植物

[6]lightreaction光反应

[7]darkreaction暗反应

[8]embed[im5bed]vt.使插入,使嵌入,

深留,嵌入,[医]包埋

[9]orientation[7R:rien5teiF[n]n.方

向,方位,定位,倾向性,向东方

[10]asymmetrical[[5simitrik[l]adj.不

均匀的,不对称的

[11]electrochemicalgradient [i9lektr[u5kemik[l5greidi[nt]n.电化学梯度

[12]lace[leis]vt.扎 带 子,扎,饰 以 花 边

vi.缚带子

[13]scaffold[5skAf[ld]n.支架

[14]plastoquinone[5plAst[ukwin[un]n.质体醌

[15]ubiquinone[ju:5bikwin[un]n.泛醌

[16]photon[5f[utRn]n.光子

[17]antennapigment[An5ten[5pigm[nt]

n.天线色素

[18]antennasystem天线(色素)系统

[19]bacteriochlorophyll[bAkti[ri[5klR:r[fil]n.细菌叶绿素

[20]carotenoid[k[5rRt[nRid]n.类胡萝卜

[21]anchor[5ANk[]v.抛锚,锚定n.锚

[22]reactioncenter作用中心

[23]exciton[5iksitRn]n.激子,激发子

[24]fluorescence[flu[5resns]n.荧光

[25]primaryphotochemicalreaction原 初

光化学反应

[26]primarychargeseparation原初电荷分离

[27]energetically[7en[55dVetik[li]adv.在能学上

[28]oxygenicphotosyntheticorganism 放

氧光合生物

[29]photosystem 光系统

[30]concurrently[k[n5kQr[nntli]adv.同

时发生地,并发地

[31]intermediate[7int[5mi:dj[t]adj.中间

[32]redoxfreeenergy氧还自由能

[33]ATPSynthaseATP合酶

[34]phosphategrouptransferpotential磷

酸基团转移势

[35]quinine[kwi5ni:n]n.奎宁,奎宁化合

[36]pheophytin[7fi:[5faitin]n.脱镁叶绿

[37]tyrosine[5tir[si:n]n.酪氨酸

[38]flavoprotein[7fleiv[u5pr[uti:n]n.黄

素蛋白

[39]Calvincycle卡尔文循环

[40]photosyntheticcarbonreductioncycle光合碳还原循环

[41]Rubisco(Dribulose1,5bisphosphate

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carboxylase/oxygenase) [ru5biskk[u]1,5二 磷 酸 核 酮 糖 羧 化 酶/加 氧

[42]anoxygenicphotosyntheticorganisms非放氧光合生物

[43]reverseelectronflow反向电子流

犈狊狊犪狔15 犇犲狊犲狉狋犘犾犪狀狋犛狌狉狏犻狏犪犾

1.Desertplantshaveadaptedtotheextremesofheatandaridity[1]byusingbothphysicalandbehavioralmechanisms,muchlikedesertanimals.Plantsthathaveadaptedbyalteringtheirphysicalstructurearecalledxerophytes[2].Xerophytes,suchascacti[3],usuallyhavespecialmeansofstoringandconservingwater.Theyoftenhavefewornoleaves,whichreducetranspiration.Phreatophytes[4]areplantsthathaveadaptedtoaridenvironmentsbygrowingextremelylongroots,allowingthemtoacquiremoistureatornearthewatertable.

2.Otherdesertplants,usingbehavioraladaptations,havedevelopedalifestyleinconformancewiththeseasonsofgreatestmoistureand/orcoolesttemperatures.Thesetypesofplantsareusually(andinaccurately)referredtoasperennials[5],plantsthatliveforseveralyears,andannuals[6],plantsthatliveforonlyaseason.

3.Desertperennialsoftensurvivebyremainingdormantduringdryperiodsoftheyear,

thenspringingtolifewhenwaterbecomesavailable.4.Mostannualdesertplantsgerminateonlyafterheavyseasonalrain,andthencompletetheirreproductivecycleveryquickly.Theybloomprodigiouslyforafewweeksinthespring,accountingformostoftheannualwildflowerexplosionsofthedeserts.Theirheatanddroughtresistantseedsremaindormantinthesoiluntilthenextyear’sannualrains.

Xerophytes5.Thephysicalandbehavioraladaptationsofdesertplantsareasnumerousandinnovativeasthoseofdesertanimals.Xerophytes,plantsthathavealteredtheirphysicalstructuretosurviveextremeheatandlackofwater,arethelargestgroupofsuchplantslivinginthedesertsoftheAmericanSouthwest.Eachofthefoursouthwesterndesertsoffershabitatsinwhichmostxerophyticplantssurvive.Buteachischaracterizedbyspecificplantsthatseemtothrive[7]there.TheGreatBasinDesert[8]isnotedforvastrollingstandsofSagebrush[9]andSaltbush[10],whileintheMojaveDesert[11]JoshuaTrees[12],

CreosoteBush[13]andBurroweed[14]predominate.TheSonoranDeserts[15]hometoanincrediblevarietyofsucculents[16],includingthegiantSaguaroCactus[17],aswellasshrubsandtreeslikemesquite[18],Paloverde[19],andIronwood[20].TheChihuahuaDesert[21]isnotedformesquitegroundcoverandshrubbyundergrowth,suchasYucca[22]

andPricklyPearCactus[23].Cactus,xerophyticadaptationsoftherosefamily,area

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mongthemostdroughtresistantplantsontheplanetduetotheirabsenceofleaves,

shallowrootsystems,abilitytostorewaterintheirstems,spinesforshadeandwaxyskintosealinmoisture.CactioriginatedintheWestIndies[24]andmigratedtomanypartsoftheNew World[25],populatingthedesertsoftheSouthwestwithhundredsofvarieties,suchastheBeavertailCactus[26]andJumpingCholla[27].Cactidependonchlorophyllintheoutertissueoftheirskinandstemstoconductphotosynthesisforthemanufactureoffood.Spinesprotecttheplantfromanimals,shadeitfromthesunandalsocollectmoisture.Extensiveshallowrootsystemsareusuallyradial,allowingforthequickacquisitionoflargequantitiesofwaterwhenitrains.Becausetheystorewaterinthecoreofbothstemsandroots,cactiarewellsuitedtodryclimatesandcansurviveyearsofdroughtonthewatercollectedfromasinglerainfall.

6.Manyotherdeserttreesandshrubshavealsoadaptedbyeliminatingleaves—replacingthemwiththorns,notspines—orbygreatlyreducingleafsizetoeliminatetranspiration.Suchplantsalsousuallyhavesmooth,greenbarkonstemsandtrunksservingtobothproducefoodandsealinmoisture.

Phreatophytes7.Phreatophytes,likethemesquitetree,haveadaptedtodesertconditionsbydevelopingextremelylongrootsystemstodrawwaterfromdeepundergroundnearthewatertable[28].Themesquite’srootsareconsideredthelongestofanydesertplantandhavebeenrecordedaslongas80feet.

8.Botanistsdonotagreeontheexactclassificationofthethreemesquitetrees:theHoneyMesquite[29],ScrewBeanMesquite[30]andtheVelvetMesquite[31],butnoonedisputesthesuccessoftheiradaptationtothedesertenvironment.Mesquitesareabundantthroughoutallthesouthwesterndeserts.TheCreosoteBushisoneofthemostsuccessfulofalldesertspeciesbecauseitutilizesacombinationofmanyadaptations.Insteadofthorns,itreliesforprotectiononasmellandtastewildlifefindunpleasant.Ithastinyleavesthatclosetheirstomata(pores)duringthedaytoavoidwaterlossandopenthematnighttoabsorbmoisture.Creosotehasanextensivedoublerootsystem,bothradialanddeep,toaccumulatewaterfrombothsurfaceandgroundwater.

Perennials9.Someperennials,suchastheOcotillo[32],survivebybecomingdormantduringdryperiods,thenspringingtolifewhenwaterbecomesavailable.Afterrainfalls,theOcotilloquicklygrowsanewsuitofleavestophotosynthesizefood.Flowersbloomwithinafewweeks,andwhenseedsbecomeripeandfall,theOcotillolosesitsleavesagainandreentersdormancy.Thisprocessmayoccurasmanyasfivetimesayear.TheOcotilloalsohasawaxycoatingonstems,whichservetosealinmoistureduringperiodsofdormancy.

10.Anotherexampleofperennialsthatutilizedormancy[33]asameansofevadingdrought

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arebulbs[34],membersofthelilyfamily[35].Thetopsofbulbsdryoutcompletelyandleavenotraceoftheirexistenceabovegroundduringdormantperiods.Theyareabletostoreenoughnourishment[36]tosurviveforlongperiodsinrockyoralluvial[37]soils.TheDesertLily,alsoknownastheAjo,isfoundatadepthof18inchesormore.Adequatewinterrainscanrouseittolifeafteryearsofdormancy.

Annuals(Ephemerals[38])

11.Theterm“annuals”impliesbloomingyearly,butsincethisisnotalwaysthecase,desertannualsaremoreaccuratelyreferredtoas“ephemerals.”Manyofthemcancompleteanentirelifecycleinamatterofmonths,someinjustweeks.

12.Contrarytotheusualideathatdesertsareuniformlyhot,dryandhomogeneousintheirlackofplantlife,theyareactuallybiologicallydiverseandcompriseamultitudeofmicroclimates[39]changingfromyeartoyear.Eachseason’suniqueprecipitation[40]patternfallsonahugevarietyofminienvironments[41].Andeachyearineachofthesetinyeconiches[42],adifferentmedley[43]ofplantsbloomasdifferentspeciesthrive.

13.Desertplantsmustactquicklywhenheat,moistureandlightinformthemit’stimetobloom.Ephemeralsarethesprintersoftheplantworld,sendingflowerstalksjettingoutinafewdays.Thepeakofthisbloommaylastforjustdaysormanyweeks,dependingontheweatheranddifferenceinelevation.Thehigheronegoes,thelaterbloomscome.

14.Differentvarietiesofplantswillbeinbloomfromdaytoday,andevenhourtohour,

sincesomeopenearlyandotherslaterintheday.EphemeralssuchastheDesertSandVerbena[44],DesertPaintbrush[45]and MojaveAster[46]usuallygerminate[47]inthespringfollowingwinterrains.Theygrowquickly,flowerandproduceseedsbeforedyingandscatteringtheirprogenytothedesertfloor.Theseseedsareextremelyhardy[48].Theyremaindormant,resistingdrought[49]andheat,untilthefollowingspring—sometimes2or3springs— whentheyrepeatthecycle,germinatingafterwinterrainstobloomagaininthespring.TherearehundredsofspeciesofephemeralsthatthriveinthedesertsoftheAmericanSouthwest.

15.Ifyouexaminedesertsoilsclosely,youwilldispelforeveranynotion[50]youmighthaveofthedesertasabarren[51]environment,foryouwilllikelyfinddozensofbothannualandperennialseedsineveryhandfulofdesertsoil.IntheSonoranDesert,seeddensitiesaveragebetween5,000and10,000persquaremeter.Theworldrecordisover200,000seedspersquaremeter.

 Notes

[1]aridity[A5riditi]n.干燥

[2]xerophyte[5zi[r[fait]n.旱生植物

[3]cactus[5kAkt[s]n.仙人掌

[4]phreatophyte[fri:5At[7fait]n.(根

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深达地下潜水层的)地下水湿生植物

[5]perennial[p[5renj[l]n.多年生植物

[6]annual[5Anju[l]n.一年生植物

[7]thrive[Wraiv]v.兴旺,繁荣,旺盛

[8]TheGreatBasinDesert(北美)大盆地

荒漠

[9]sagebrush[5seidVbrQF]n.山艾树

[10]saltbush[5sRlt7buF]n.[植]滨藜

[11]theMojave[m[u5hB:vi]Desert莫哈

维沙漠(在美国加利福尼亚西南)[12]Joshua[5dVRFw[]Trees约书亚树

[13]creosote[5kri[s[ut]Bush石炭酸灌木

[14]burroweed[5bQr[uwi:d]木碱蓬

[15]TheSonoran[sR:5nR:rB:]Desert索

诺兰沙漠

[16]succulent[5sQkjul[nt]n.肉 质 植 物,多汁植物adj.多 汁 的,多 水 分 的,多

汁性的

[17]Saguaro[s[5gwB:r[u]Cactus树形仙

人掌

[18]mesquit[meskwit]n.牧豆树;豆科灌

[19]paloverde[7pAl[u5v[:d]n.[植]假紫

荆属树木

[20]ironwood[5ai[wJd]n.铁木,硬木

[21]TheChihuahua[tFi5wB:w[:]Desert奇华华荒漠;Chihuahua吉娃娃(一 种

产于墨西哥的狗)[22]yucca[5jQk[]n.丝兰(一种丝兰属常

绿植物)[23]PricklyPearCactus刺梨仙人掌

[24]theWestIndies西印度群岛

[25]theNewWorld新世界(即美洲大陆)[26]beavertail[5bi:v[teil]Cactus獭 尾 仙

人掌

[27]JumpingCholla[5tF[uj[]跳月掌(这

种仙人掌 看 起 来 就 像 在 山 谷 中 跳 跃 一

样)

[28]watertable地下水位

[29]HoneyMesquiten.蜜豆灌木

[30]ScrewBeanMesquiten.一种豆科灌木

[31]theVelvetMesquite天鹅绒豆灌木

[32]Ocotillo[[U9k[5ti:l[U]n.墨西哥刺

木(一种仙人掌)[33]dormancy[5dR:m[nsi]n.休眠

[34]bulb[bQlb]n.鳞茎植物;鳞茎

[35]lilyfamily百合科

[36]nourishment[5nQriFm[nt]n.食 物,营养品

[37]alluvial[[5lu:vj[l]adj.冲 积 的,淤

积的

[38]ephemeral[i5fem[r[l]n.短 命 植 物

adj.朝生暮死的,短暂的,短命的

[39]microclimate [5maikr[Jklaimit]n.[气]小气候(指森林、城市、洞穴等局部

地区的气候)[40]precipitation[pri7sipi5teiF[n]n.降

[41]minienvironment微环境

[42]econiche[5i:k[unitF]n.生态小生境

[43]medley[5medli]n.混杂的人群,杂乱

的一团,混 合 物,杂 录,[音]集 成 曲

adj.混合的,拼凑的

[44]DesertSandVerbena[v[:55bi:n[]荒

漠黄花秋水仙

[45]DesertPaintbrush荒漠画笔树

[46]MojaveAster[5Ast[]摩哈比菊花

[47]germinate[5dV[:mineit]v.萌发

[48]hardy[5hB:di]adj.难的,艰苦的,勇敢的,抗性强的

[49]droughtn.干旱

[50]notion[5n[uF[n]n.概念,观念,想

法,意见,打算,主张

[51]barren[5bAr[n]adj.不 生 育 的,不

孕的,贫瘠 的,没 有 结 果 的,无 益 的,单调的,无聊的,空洞的

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犝犖犐犜05 犌犈犖犈犜犐犆犛犃犖犇犈犞犗犔犝犜犐犗犖

犈狊狊犪狔16 犕犲狀犱犲犾’狊犌犲狀犲狋犻犮犔犪狑狊

1.Onceuponatime(1860’s),inanAustrianmonastery[1],therelivedamonknamedMendel,GregorMendel[2].MonkshadalotoftimeontheirhandsandMendelspenthistimecrossingpeaplants.Ashedidthisoverandoveragain,henoticedsomepatternstotheinheritanceoftraits[3]fromonesetofpeaplantstothenext.Bycarefullyanalyzinghispeaplantnumbers(hewasreallygoodatmathematics),hediscoveredthreelawsofinheritance:theLawofDominance[4],theLawofSegregation[5]andtheLawofIndependentAssortment[6].

2.Now,noticeinthatverybriefdescriptionofhisworkthatthewords“chromosomes”or“genes”arenowheretobefound.Thatisbecausetheroleofthesethingsinrelationtoinheritancehadnotbeendiscoveredyet.WhatmakesMendel’scontributionssoimpressiveisthathedescribedthebasicpatternsofinheritancebeforethemechanism[7]forinheritance(namelygenes)wasevendiscovered.

TheLawofDominance— Mendel’sFirstLaw3.Stated“simply”,itgoeslikeso:Inacrossofparentsthatarepureforcontrastingtraits[8],onlyoneformofthetraitwillappearinthenextgeneration.Offspringthatarehybridforatraitwillhaveonlythedominanttrait[9]inthephenotype[10].

4.WhileMendelwascrossinghispeaplants,henoticedsomethinginteresting.Whenhecrossedpuretallplantswithpureshortplants,allthenewpeaplants(referredtoastheF1generation)weretall.Similarly,crossingpureyellowseededpeaplantsandpuregreenseededpeaplantsproducedanF1generationofallyellowseededpeaplants.Thesamewastrueforotherpeatraits:

ParentPeaPlants F1PeaPlants

tallstem×shortstem alltallstems

yellowseeds×greenseeds allyellowseeds

greenpeapods[11]×yellowpeapods allgreenpeapods

roundseeds× wrinkled[12]seeds allroundseeds

axialflowers[13]×terminal[14]flowers allaxialflowers

  So,whathenoticedwasthatwhentheparentplantshadcontrastingformsofatrait

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(tallvsshort,greenvsyellow,etc.)thephenotypesoftheoffspringresembledonlyoneoftheparentplantswithrespecttothattrait.

5.Now,inourmodernwisdom,weuse“allele”[15]or“gene”insteadofwhatMendelcalled“factors”.ThereisageneintheDNAofpeaplantsthatcontrolsplantheight(makesthemeithertallorshort).Oneformofthegene(allele)codes[16]fortallandtheotheralleleforplantheightcodesforshort.Forabbreviations,weusethecapital“T”forthedominanttallallele,andthelowercase[17]“t”fortherecessive[18]shortallele.Let’srevisitthethreepossiblegenotypes[19]forpeaplantheightandaddsomemorevocabulary.

GenotypeSymbol GenotypeVocab Phenotype

TT homozygous[20]DOMINANTorpuretall tall

Tt heterozygous[21]orhybrid tall

tt homozygousRECESSIVEorpureshort short

  Note:theonlywaytherecessivetraitshowsupinthephenotypeisifthegenotypehas2lowercaseletters(i.e.ishomozygousrecessive).Alsonote:hybridsalwaysshowthedominanttrait[22]intheirphenotype(that,bytheway,isMendel’sLawofDominance).

TheLawofSegregation — Mendel’sSecondLaw6.Duringtheformationofgametes(eggsorsperm),thetwoallelesresponsibleforatrait,areseparatedfromeachother.Allelesforatraitarethen“recombined”atfertilization,producingthegenotypeforthetraitsoftheoffspring.

Parents F1Offspring

Genotype(s) TT×tt 100% Tt

Phenotype(s) tall×short 100%tall

  So,hetakestwoofthe“F1”generation(whicharetall)andcrossesthem.Hewasprobablyfiguringthathe’sgonnagetalltallagain(sincetallisdominant).Butno!Hegotsomeshortplantsfromthiscross!Hisnewbatchofpeaplants(the“F2”generation)isabout3/4talland1/4short.

ParentPeaPlants(TwoMembersofF1Generation) Offspring(F2Generation)

Genotypes:

Tt× Tt

Phenotypes:

tall×tall

Genotypes:

25% TT

50% Tt

25%tt

Phenotypes:

 75%tall

25%short

TheLawofIndependentAssortment— Mendel’sThirdLaw7.Allelesfordifferenttraitsaredistributedtosexcellsindependentlyofoneanother.So

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farwe’vebeendealingwithonetraitatatime.Forexample,height(tallorshort),

seedshape(roundorwrinkled),podcolor(greenoryellow),etc.Mendelnoticedduringallhisworkthattheheightoftheplantandtheshapeoftheseedsandthecolorofthepodshadnoimpact[23]ononeanother.Inotherwords,beingtalldidn’tautomaticallymeantheplantshadtohavegreenpods,nordidgreenpodshavetobefilledonlywithwrinkledseeds,thedifferenttraitsseemtobeinheritedindependently.

8.Pleasenotetheemphasisontheword“different”.Ninetimesoutoften,inaquestioninvolvingtwodifferenttraits,youranswerwillbe“independentassortment”.Itinvolveswhat’sknownasa“dihybridcross”[24],meaningthattheparentsarehybridfortwodifferenttraits.

9.Thegenotypesofourparentpeaplantswillbe:RrGg×RrGg,where“R”=dominantalleleforroundseeds,“r”=recessivealleleforwrinkledseeds,“G”=dominantalleleforgreenpods,and“g”=recessivealleleforyellowpods.

10.Noticethatwearedealingwithtwodifferenttraits:(1)seedtexture[25](roundorwrinkled),and(2)podcolor(greenoryellow).Noticealsothateachparentishybridforeachtrait(onedominant&onerecessivealleleforeachtrait).

11.Weneedto“split”thegenotypelettersandcomeupwiththepossiblegametesforeachparent.Keepinmindthatagamete(sexcell)shouldgethalfasmanytotalletters(alleles)astheparentandonlyoneofeachletter.Soeachgameteshouldhaveone“are”

andone“gee”[26]foratotaloftwoletters.Therearefourpossiblelettercombinations:

RG,Rg,rG,andrg.Thesegametesaregoing“outside”thepsquare[27],above4columnsandinfrontof4rows.Wefillthingsinjustlikebefore— “lettersfromtheleft,

lettersfromthetop”.Whenwefinisheachbox,wegetsfourletterstotal(two“are’s”

andtwo“gees”).Thisiswhatitlookslike:

RG Rg rG rg

RGRRGGround

RRGground

RrGGround

RrGground

RgRRGground

RRgground

RrGground

Rrgground

rGRrGGround

RrGground

rrGGwrinkled

rrGrwrinkled

rgRrGground

Rrgground

rrGgwrinkled

rrggwrinkled

12.Theresultsfromadihybridcrossarealwaysthesame:9/16boxes(offspring)showdominantphenotypeforbothtraits(roundandgreen),3/16showdominantphenotypeforfirsttraitandrecessiveforsecond(roundandyellow),3/16showrecessivephenotypeforfirsttrait&dominantformforsecond(wrinkledandgreen),and1/16showrecessiveformofbothtraits(wrinkledandyellow).

13.So,asyoucanseefromtheresults,agreenpodcanhaveroundorwrinkledseeds,and

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thesameistrueofayellowpod.Thedifferenttraitsdonotinfluencetheinheritanceofeachother.Theyareinheritedindependently.

14.Interestingtonoteisthatifyouconsideronetraitatatime,wegettheusual3∶1ratioofasinglehybridcross.Forexample,justcomparethecolortraitintheoffspring:12greenand4yellow (3∶1dominant:recessive).Samedealwiththeseedtexture:12round&4wrinkled(3∶1ratio).Thetraitsareinheritedindependentlyofeachother.

 Notes

[1]monastery[5mRn[stri]n.修道院,僧

[2]GregorMendel孟 德 尔(1822~1884)奥地利遗传学家

[3]trait[treit]n.性状

[4]theLawofDominance[5dRmin[ns]显性定律

[5]theLawofSegregation[7segri5geiF[n]分离定律

[6]theLawofIndependentAssortment[[5sR:tm[nt]独立分配定律

[7]mechanism[5mek[niz[m]n.机制

[8]contrastingtrait相对性状

[9]dominanttrait显性性状

[10]phenotype[5fi:n[taip]n.表型

[11]pod[pRd]n.豆荚

[12]wrinkled[5riNkld]adj.具皱的

[13]axialflowers茎间花

[14]terminalflowers茎顶花

[15]allele[[5li:l]n.等位基因

[16]code[k[ud]v.编码

[17]lowercase小写字母

[18]recessive[ri5sesiv]adj.隐性的

[19]genotype[5dVen[taip]n.基因型

[20]homozygous[7hRm[5zaig[us]adj.纯

合的

[21]heterozygous[7het[r[u5zaig[s]adj.杂合的

[22]dominanttrait显性性状

[23]impact[5impAkt]n.碰撞,冲击,冲

突,影响,效果

[24]dihybrid[dai5haibrid]cross双因子杂

种杂交

[25]texture[5tekstF[]n.纹理

[26]one“are”andone“gee”一个R或r和

一个G或g[27]psquaren.P方阵

犈狊狊犪狔17 犠犺犪狋犻狊犪犌犲狀犲狋犻犮犕犪狆[1]?

1.Ageneticlinkagemap[2]showstherelativelocationsofspecificDNAmarkers[3]along

thechromosome.Eachmarkerislikeamilemarker[4]alongahighway.Anyinherited

physicalormolecularcharacteristicthatdiffersamongindividualsandiseasilydetecta

bleisapotentialgeneticmarker[5].MarkerscanbeexpressedDNAregions(genes)or

DNAsegmentsthathavenoknowncodingfunctionbutwhoseinheritancepattern[6]can

befollowed.DNAsequencedifferencesareespeciallyusefulmarkersbecausetheyare

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plentifulandeasytocharacterizeprecisely.Markersmustbepolymorphic[7]tobeusefulinmapping;thatis,alternativeforms(alleles)mustexistamongindividualssothattheyaredetectableamongdifferentmembersinthemappingpopulation[8].

2.Amappingpopulationisthegroupofindividualsthatwillbeevaluatedfortheir“score”

atasetofmarkers.Thisrawmappingdataisanalyzedbysoftware,whichconstructsthemapbyobservinghowfrequentlytheallelesatanytwomarkersareinheritedtogether.Thecloserthemarkersare,thelesslikelyitisthatarecombinationevent[9](acrossover[10]duringmeiosis)willseparatethealleles,andthemorelikelyitisthattheywillbeinheritedtogether.Thus,unlikeothertypesofmaps,thedistancebetweenpointsonageneticmapisnotmeasuredinanykindofphysicalunit;itisareflectionoftherecombinationfrequency[11]betweenthosetwopoints.Thisgeneticmapunitismeasuredintermsofcentimorgans(cM)[12](namedafterthegeneticistThomasHuntMorgan[13]).Twomarkersaresaidtobe1cMapartiftheyareseparatedbyrecombination1% ofthetime.Thegeneticdistance[14]tellsyoulittleaboutthephysicaldistance[15]—theactualamountofDNAseparatingthemarkers.Thisgenetictophysicaldistancerelationshipvariesbetweenspecies,andvariesbetweendifferentspotswithinthegenomeofasinglespecies.

3.Ageneticmaphelpsusunderstandthestructure,functionandevolutionofthegenome.Itcanbeanimportanttoolforagriculturalcropimprovement.Recentworkhasshownthatthegeneticmapsofmanycloselyrelatedspecies(forexample,thegrains)arequitesimilarwithrespecttothecontentandlocationofgenes,andscientistsaretryingtodeterminehowthegeneticmapofonespeciesmaybeappliedtoothers.

4.Manydifferenttypesofobjectscanbeassignedapositiononageneticmap.Wewilldividetheseobjectsintotwocategories:“point”objectsand“interval”objects.Knowngenesandmolecularmarkersareexamplesofpointonmaps.Centromeres[16],quantitativetraitloci(QTLs)[17],rearranements,introgressions[18],syntenic[19]regionsandcontigs[20]couldbeexamplesofintervals.

5.Noteverydatabasewillcontainallthesetypesofobjects,orrepresentthesameobjectinthesameway!Forexample,incertaindatabases,aQTLmaybeassignedaspecificpointlocationonamap;inothers,aQTLmaybedefinedtospanaparticularregionofthemap.

 Notes

[1]geneticmapn.遗传图

[2]geneticlinkagemapn.遗传连锁图

[3]specificDNAmarkern.特异DNA标

[4]milemarkern.里程计

[5]geneticmarkern.遗传标记

[6]inheritancepattern[in5herit[ns5pAt[n]n.遗传模式

[7]polymorphic[9pRli5mC:fik]adj.多

态性的

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[8]mappingpopulationn.作图群体

[9]recombinationeventn.重组事件

[10]crossovern.交叉

[11]recombinationfrequencyn.重组频率

[12]centimorgan(cM)[senti5mR:g[n]n.(遗)厘摩(基因交换单位)

[13]ThomasHuntMorgann.摩尔根(1866~1946),美 国 细 胞 遗 传 学 家。他 提 出

了“基因论”,他认为基因在染色体上呈

直线排列,从而确立了不同基因与性状

之间的对应关系。

[14]geneticdistancen.遗传距离

[15]physicaldistancen.物理(实际)距离

[16]centromere[5sentr[7mi[]n.(染色体

上的)着丝粒

[17]quantitativetraitloci [5l[usai](QTLs)n.数量性状位点

[18]introgression[7intr[5greF[n]n.基因

渗入,渐渗现象

[19]syntenic[sin5tenik]adj.基因共线

[20]contig[k[ntig]n.重叠群

犈狊狊犪狔18 犅犻狅犾狅犵犻犮犪犾犈狏狅犾狌狋犻狅狀

1.Conceptthatembodiesthebeliefthatexistinganimalsandplantsdevelopedbyaprocessofgradual,continuouschangefrompreviouslyexistingforms,thistheory,alsoknownasdescentwithmodification[1],constitutesorganicevolution[2].Inorganicevolution[3],

ontheotherhand,isconcernedwiththedevelopmentofthephysicaluniversefromunorganizedmatter.Organicevolution,asopposedtobeliefinthespecialcreationofeachindividualspeciesasanimmutable[4]form,conceivesoflifeashavinghaditsbeginningsinasimpleprimordialprotoplasmicmass[5](probablyoriginatinginthesea)fromwhich,throughthelongerasoftime,aroseallsubsequentlivingforms.

HistoryofEvolutionaryTheory —EarlyTheories2.EvolutionaryconceptsappearedinsomeearlyGreekwritings,e.g.intheworksofThales[6],Empedocles[7],Anaximander[8],andAristotle[9].Undertherestraining[10]

influenceoftheChurch,noevolutionarytheoriesdevelopedduringsome15centuriesoftheChristianera[11]tochallengethebeliefinspecialcreationandtheliteralinterpretationofthefirstpartofGenesis[12];however,muchdatawasaccumulatedthatwastobeutilizedbylatertheorists[13].Withthegrowthofscientificobservationandexperimentation,therebegantoappearfromaboutthemiddleofthe16thcentury.Glimpsesofthetheoryofevolutionemergedinthemid19thcentury.Theinventionofthemicroscope,makingpossiblethestudyofreproductivecellsandthegrowthofthescienceofembryology[14],wasafactorinoverthrowinghampering[15]theoriesfoundedinfalseideasofthereproductiveprocess;studiesinclassification(taxonomy[16]orsystematics[17])

andanatomy,basedondissection[18],werealsoinfluential.3.Linnaeus[19],inhislateryears,showedaninclinationtowardbeliefinthemutabilityofspeciesasaresultofhisobservationsofthemanyvariationsamongspecies.Buffon[20],

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onthebasisofhisworkincomparativeanatomy,suggestedtheinfluenceofuseanddisuse[21]inmoldingtheorgansofvertebrateanimals.Lamarck[22]wasthefirsttopresentaclearlystatedevolutionarytheory,butbecauseitincludedtheinheritanceofacquiredcharacteristics[23]astheoperativeforce[24]ofevolution,hiswholetheorywasridiculedanddiscredited[25]formanyyears.

Darwinism[26]

4.Althoughspecialcreationofeachspecieswastheprevalent[27]beliefevenamongscientistsinthefirsthalfofthe19thcentury,theevidenceinfavorofevolutionhadbythattimebeenuncovered.Itremainedforsomeonetoassembleandinterprettheevidenceandtoformulateascientificallycredible[28]theory.ThiswasaccomplishedsimultaneouslybyA.R.Wallace[29]andCharlesRobertDarwinwhosetforththeconceptsthatcametobeknownasDarwinism.In1859appearedthefirsteditionofDarwin’sOriginofSpecies[30].Theinfluenceofthisevolutionarytheoryuponscientificthoughtandexperimentationcannotbeoverestimated.Intheyearsfollowingthepromulgation[31]ofDarwin’stheoryofevolution,manyacceptedandmanydenieditsvalidity[32].

5.Thetheoryfoundanopposingforceinsomereligiouscreeds[33]thatdeclareditincompatible[34]withtheirbasictenets[35].Foratimeevolution,sometimesfalselyinterpretedasmeaninghumandescentfrommonkeysratherthandescentfromanancientandextinctancestor,becameatargetforattackbybothchurchandeducationalauthorities.FeelingranhighevenaslateasthetimeoftheScopestrial[36].Nevertheless,thetheoryofevolutionbecamefirmlyentrenched[37]asascientificprinciple,andinmostcreedsithasbeenreconciled[38]withreligiousteachings.SomeChristianfundamentalists[39],

however,donotacceptthetheoryandhavestriventohavebiblicalcreationism[40]

taughtintheschoolsasanalternativetheory.

ModernEvolutionaryTheory6.Evolutionarytheoryhasundergonemodificationinthelightoflaterscientificdevelopments.Asmoreandmoreinformationhasaccumulated,thefactsfromanumberoffieldsofinvestigationhaveprovidedcorroboration[41]andmutualsupport.EvidencethatevolutionhasoccurredstillrestssubstantiallyonthesamegroundsthatDarwinemphasized;comparativeanatomy,embryology,geographicaldistribution[42],andpaleontology[43].Butadditionalrecentevidencehascomefrombiochemistryandmolecularbiology,whichrevealsfundamentalsimilaritiesandrelationsinmetabolismandhereditarymechanismsamongdisparate[44]typesoforganisms.Ingeneral,bothatthevisiblelevelandatthebiochemical,onecandetectthekindsofgradationsofrelatednessamongorganismsexpectedfromevolution.

7.ThechiefweaknessofDarwinianevolutionlayingapsinitsexplanationsofthemechanismofevolutionandoftheoriginofspecies.TheDarwinianconceptofnaturalselectionisthatinheritablevariationsamongtheindividualsofgiventypesoforganismscon

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tinuallyariseinnatureandthatsomevariationsproveadvantageousunderprevailingconditionsinthattheyenabletheorganismtoleaverelativelymoresurvivingoffspring.ButhowthesevariationsinitiallyariseoraretransmittedtooffspringandhencetosubsequentgenerationswerenotunderstoodbyDarwin.Thescienceofgenetics,originatingatthebeginningofthe20thcenturywiththerecognitionoftheimportanceoftheearlierworkofMendel,providedasatisfactoryexplanationfortheoriginandtransmissionofvariation.In1901,deVries[45]presentedhistheorythatmutation,orsuddenlyappearingandwelldefinedinheritablevariation(asopposedtotheslight,cumulativechangesstressedbyDarwin),isaforceintheoriginandevolutionofspecies.Mutationingenesisnowacceptedbymostbiologistsasafundamentalconceptinevolutionarytheory.Thegeneisthecarrierofheredityanddeterminestheattributesoftheindividual;thuschangesinthegenescanbetransmittedtotheoffspringandproduceneworalteredattributesinthenewindividual.

8.Stillprevalentmisunderstandingsofevolutionarethebeliefsthatananimalorplantchangesinordertobetteradapttoitsenvironment—forexample,thatitdevelopsaneyeforthepurposeofseeing—andthatactualphysicalcompetitionamongindividualsisrequired.Sincemutationisarandomprocess,changescanbeuseful,unfavorable,orneutraltotheindividual’sorspecies’survival.However,anewcharacteristicthatisnotdetrimental[46]maysometimesbetterenabletheorganismtosurviveorleaveoffspringinitsenvironment,especiallyifthatenvironmentischanging,ortopenetrate[47]

anewenvironment—suchasthedevelopmentofalunglikestructurethatenablesanaquaticanimaltosurviveonland(lungfish[48]),wheretheremaybemorefoodandfewerpredators.

 Notes

[1]descentwithmodificationn.修饰演化

[2]organicevolutionn.有机进化

[3]inorganicevolutionn.无机进化

[4]immutable[i5mju:t[bl]adj.不 可 变

的,不变的,不能变的,永恒的

[5]primordial[prai5mR:dj[l]protoplasmicmassn.原始原生质浆

[6]Thales[5Weili:z]n.泰 利 斯(624~546BC),古希腊哲学家、数学家、天文

学家,希腊“七贤”之一。[7]Empedoclesn.恩 培 多 克 勒(493~433BC),古希腊哲学家。认为组成世界的

四大元素 分 别 是 火(fire)、水(water)、土(earth)和气(air)。

[8]Anaximandern.阿那克西曼德(约公元

前610年~前547年),古希腊哲学家、米 利 都 学 派 的 学 者、泰 勒 斯 的 学 生。据说他还是在希腊第一个绘 制 地 图 的

人。阿那克西曼德还 曾 经 担 任 过 一 个

米利都殖 民 地 的 领 袖。阿 那 克 西 曼 德

认为,构成万物的元素是所谓 的“无 限

者”,世 界 从 它 产 生,又 复 归 于 它。他

还认为,地 球 是 一 个 自 由 浮 动 的 圆 柱

体,人类处于圆柱体 的 一 端 表 面 之 上,而我 们 的 世 界 只 是 无 数 世 界 中 的 一

个。阿那 克 西 曼 德 还 认 为,人 从 海 鱼

演化而来。[9]Aristotle[5AristRtl]n.亚 里 士 多 德

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56   

(公元前384~前322),古 希 腊 大 哲 学

家、科学家。[10]restraining[ristreiniN]adj.抑 制 的,

遏制的,控制的

[11]Christianera[5kristj[n5i[r[]公元纪

年,公元

[12]Genesis[5dVenisis]n.(圣经)创世记

[13]theorist[5Wi[rist]n.理论家,空谈家

[14]embryology[7embri5Cl[dVi]n.胚胎

[15]hamper[5hAmp[]v.妨碍,牵制

[16]taxonomy[tAk5sRn[mi]n.分类学

[17]systematics[7sisti5mAtiks]n.系 统

学 (=taxonomy)[18]dissection[di5sekF[n]n.解剖

[19]Linnaeus[li5ni:[s]n.林 奈(1707~1778)瑞典自然学者,奠 定 了 现 代 生 物

学分类命名的基础。[20]Buffon[5bu:f[u]n.布 丰(Georges

LouisLeclerc,ComtedeBuffon,1707~1788),法国 博 物 学 家、数 学 家、生 物

学家、宇 宙 学 家 和 作 家。布 丰 的 思 想

影响了 之 后 两 代 的 博 物 学 家,包 括 达

尔文和拉马克。[21]useanddisusen.用和废用

[22]Lamarck[l[5ma:k]n.拉马克 (法国

博物学家,1744~1829)[23]acquiredcharacteristicsn.获得性状

[24]operativeforcen.运转力

[25]discreditv.不信,怀疑

[26]Darwinism[5dB:winiz[m]n.达尔文

学说,进化论

[27]prevalent[5prev[l[nt]adj.普 遍 的,流行的

[28]credible[5kredibl]adj.可信的

[29]A.R.Wallacen.华莱士(A.R.AlfredRusselWallace,1823~1913)英 国 博

物学家、进 化 论 者,与C.R.达 尔 文 共

同提出 自 然 选 择 学 说,动 物 地 理 学 的

奠基人。[30]OriginofSpecies物种起源

[31]promulgation[9prCm[l5geiF[n]n.颁布

[32]validity[v[5liditi]n.有效性,合法性,正确性

[33]creed[kri:d]n.信条

[34]incompatible[7ink[m5pAt[bl]adj.不相容的

[35]tenet[5tenit]n.原则

[36]Scopestrial斯克普斯审判,著名的“猴

子”审判,即1925年田纳西州的斯克普

斯案的审判。当时田纳 西 州 通 过 了 一

部法律,禁 止 公 立 学 校 讲 授 达 尔 文 的

进化论。高 中 科 学 教 师、24岁 的 约 翰

·斯 克 普 斯(JohnT.Scopes)同 意 在

一个试 验 性 的 案 件 中 扮 演 被 告,充 当

牺牲的羔羊。这场审判 在 科 学 和 守 旧

的宗教之间引发了一场引人注 目 的 对

抗,案 件 审 判 轰 动 一 时。在 斯 克 普 斯

审判的 传 奇 故 事 中,该 案 是 一 个 转 折

点;斯克普斯输了,但是科学却赢了。[37]entrench[in5trentF]v.以壕沟防护

[38]reconcile[5rek[nsail]vt.使 和 解,使

和谐

[39]Christianfundamentalist [5kristj[

fQnd[5ment[list]n.信 奉 正 统 派 基 督

教的人

[40]biblicalcreationism[5biblik[lkri:5eiF[niz[m]n.(圣 经)创 造 宇 宙 说,特 别

创造说

[41]corroboration[k[rRb[5reiF[n]n.确

证的事实,确证

[42]geographicaldistributionn.地理分布

[43]paleontology[7pAliRn5tRl[dVi]n.古生物学

[44]disparate[5disp[rit]adj.全异的

[45]deVriesn.德弗里斯 (人名)[46]detrimental[7detri5mentl]adj.有 害

[47]penetrate[5penitreit]v.穿 透,渗 透,看穿,洞察

[48]lungfish[5lQNfiF]n.肺鱼

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犝犖犐犜06 犎犝犕犃犖犃犖犃犜犗犕犢犃犖犇犘犎犢犛犐犗犔犗犌犢

犈狊狊犪狔19 犜犺犲犎狌犿犪狀犅狉犪犻狀

1.Thehumanbrain,whenexposed,looksratherlikeanenormouswalnut[1].Itweighsaboutthreeorthreeandahalfpoundsandismadeup,likeotherorgans,ofcells.Unlikeawalnut,ithasbeenmappedoutinminute[2]detail.

2.SincethemenwhofirstdissectedthebrainusedLatinandGreek,thevariouspartsofthebrainhaveLatinorGreeknames:thebrainitselfisthecerebrum[3]andthewrinkledouterlayeristhecortex[4];thesmallridgedprojectionatthebackiscalledthecerebellum[5](‘littlebrain’),andsoon.

3.Thecortex,about1or4mmthick,enclosesthetwomostnotablepartsofthebrainthecerebralhemispheres[6].These,almostbutnotquitemirrorimages[7]ofoneanother,togetherconstitutethecerebrum;andeachhemisphereinturnisdividedintolobes[8],the“continents”ofthecerebrum:atthefront,thefrontallobe[9];attheside,

thetemporallobe[10];ontop,theparietallobe[11];andatthebackofthehead,theoccipitallobe[12].Eachlobeisroughlyassociatedwithadifferentfunction.

4.Thetwohemispheresarejoinedbythickwhitishfibers,thecorpuscallosum[13];nearthemarethelimbiclobe[14](concernedwithemotion)andtheeggshapedthalamus[15]

(‘bedroom’!)nearthecenterofthebrain;belowthelatteristhehypothalamus[16]

whichisresponsibleforbodytemperature,amongotherthings.5.Themidbrainismuchsmaller.Amongitsdutiesareresponsestosightandsoundandcontrolofsleepingandwaking.Thehindbrainincludesthecerebellum(involvedinthemanagementofmovement)andthetinylumpsandbumpswhichhavefunctionstoonumeroustomention.

6.Midbrainandhindbrainareoftengroupedtogetherandcalledbrainstem[17],oneofthefeweasilyunderstoodtermsintheneurosciences[18].

7.Connectingthebrainstemtotherestofthebodyisthespinalcord[19].Partsofthespinalcordhavetheirownfunction:soldierstothebrain’sgeneral.Butmostlyitcontainsfiberswhichconnectthebraintomusclesandsenseorgansthroughoutthebody.

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 Notes

[1]walnut[5wC:ln[t]n.胡桃,核桃树

[2]minute[mai5nju:t]adj.微 小 的,详

细的,仔细而准确的

[3]cerebrum[5seribr[m]n.大脑

[4]cortex[5kR:teks]n.皮层

[5]cerebellum[7seri5bel[m]n.小脑

[6]cerebralhemisphere[5seribr[l5hemisfi[]n.大脑半球

[7]mirrorimage[5mir[5imidV]n.镜像

[8]lobe[l[ub]n.脑叶

[9]frontal[5frQntl]lobe前叶

[10]temporal[5temp[r[l]lobe颞叶

[11]parietal[p[5rai[t[l]lobe顶叶

[12]occipital[Rk5sipitl]lobe枕叶

[13]corpuscallosum[5kR:p[skC:l[s[m]

n.胼胝体

[14]limbic[5limbik]lobe侧叶

[15]thalamus[5WAl[m[s]n.丘脑

[16]hypothalamus[7haip[u5WAl[m[s]

n.下丘脑

[17]brainstemn.脑干

[18]neuroscience[7nju[r[u5sai[ns]n.神

经科学

[19]spinal[5spainl]cordn.脊索

犈狊狊犪狔20 犇犻犪犵狀狅狊犻狊:犉犲犿犪犾犲

1.Medicalscienceislearningthatsexdoesmakeadifference.Men’sandwomen’sbodieseachhavetheirownhealthproblems,reactdifferentlytodrugsandoftenrequiredifferenttreatments.Webringyousomeofthelatestthinking:

ImmuneComplexity2.A woman’simmunesystemdisplaysanexquisite[1]amountofcontrolthataman’scan’treplicate.It’sstillnotclearwhy,butthefemalebody’sdefensestendtomountmoreaggressiveresponsestoinvadingmarauders[2];then,duringpregnancy,thisresponseisdampened(reduced)considerablytoaccommodate[3]thefetus[4].Perhapsowingtothisonoffintensity,womenaremorepronetodevelopinglupus[5],rheumatoidarthritis[6]andmultiplesclerosis[7],allconditionsinwhichtheimmunesystemattackshealthytissues.

3.Researchersarejustbeginningtostudywhyestrogen[8]mightcausethedefensesystemtorev[9]intooverdriveinthesecases.

HabitsoftheHeart4.Theclassicchestcrushing[10]painthatisthehallmark[11]ofaheartattackturnsouttobemainlyamalesymptom[12].Women’sheartattacks,bycontrast,tendtoshowupasshortnessofbreath,fatigueandjawpain,stretchedoutoverhoursratherthanmi

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nutes.5.Womentendtosuffertheirfirstheartattack10yearsolderthanmen.Yet,partlybecausethewomenareolder,thoseheartattacksaremoreoftenfatal.Thisisapostmenopausal[13]phenomenon,atradeoff[14]foryearsofprotectionfromestrogen.Stayingbathedinthehormonekeepsbloodvesselselasticandfreeofhardened/plaqueformations.Estrogenalsoinstructsthelivertochurnout[15]moreHDL[16],orgoodcholesterol[17],whichpullsplaqueawayfromarterywalls.

6.Drugscommonlyusedtobreakupclotsandstabilizeerraticheartbeats[18]arelesseffectiveinwomenthaninmen.Hormonereplacementtherapy[19]withestrogenandprogestin[20]hasbeenshowntohelp.A USGovernmentstudyiscurrentlyunderwaythataimstoclarifyhowestrogenworksontheheart,brainandbreast.

ReproductiveOrgans7.Advancesindiagnosticexams[21]andhormonetreatmentshavedrasticallycuttheincidenceofcanceroftheuterus[22],ovaries[23]andcervix[24]overthepastfivedecades.Papsmears[25]thatdetectabnormalcellsinthecervixbeforetheybecomemalignant[26]havecontributedtoa75%dropincervicalcancer[27]sincethe1950s.Wideruseofbirthcontrolpillsandhormonereplacementtherapyhavedecreasedtheriskofovariananduterine[28]cancers.Recentresearchalsosuggeststhatinsomecases,alowfatdietcancuttheriskofcervicalcancerevenfurther.

RiskoftheKnee8.Aswomenparticipateinmoreandmoresports,orthopedists[29]arenoticingadifferenceinthetypesofinjurieswomenareproneto.Theyappeartobemoresusceptiblethanmentodamagingtheligaments[30]thatholdthekneetogether.Manywomenbasketball

playershavesufferedpainfulandpotentiallydebilitatingtears[31]totheanteriorcrusiateligament[32],whichcantakemonthstoheal.Doctorsthinkitmayhavesomethingtodowithawoman’swiderhips,whichplaceagreaterstrainontheligamentsjoiningthethigh[33]totheknee.Theseligamentsareweakerinwomentostartwith.

SlowerMetabolism9.Womentendtometabolizeanumberofdrugsdifferentlyfrommen:

Alcohol:ittakesfewerdrinksforawomantofeeltheeffects[34],becausetheliverbreaksdownalcoholmoreslowly,leavingmoreofitfloatingintheblood.Aspirin[35]:thepainkillertakeslongertoclearawoman’ssystem.Becauseitkeeps

platelets[36]fromclotting,aspirinshouldbeavoidedbypregnantwomen.Itcantriggerbleedinginthefetalbrain.Betablockers[37]:BecausedrugslikeInderal,prescribedtoreducebloodpressureandmigrainepain[38],takelongertometabolizeinwomenthaninmen,thedosagemustbe

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carefullymonitoredtoavoidsideeffects.TricyclicAntidepressants[39]:womentakingoralcontraceptives[40]mayneedlowerdosesofthesedrugstotreattheirdepression,sincethePill[41]keepslevelsofthedrugsinthebodyhigh.

MindandMood10.Womenaremorepronetodepressionthanmen,andthereasonmayhaveasmuchtodo

withbiologyasithaswithstressandotherlifestylefactors.Evidenceismountingthatthemaleandfemalebrainsmayresponddifferentlytohormonesandbrainchemicals.Womenproducelessserotonin[42],amoodregulatingchemical,thanmen,andaremoresensitivetochangesinserotoninlevels,whichareinturnregulatedbyestrogen.Womenthusrespondbettertodrugsaffectingtheserotoninsystem,whilementendtorespondbettertodrugsthatalsoaffectnorepinephrine[43],aneurotransmittersecretedbytheadrenalglands[44]andbynerveendingsduringstress.

11.Estrogenmaystaveoff[45]thedementia[46]andmemorylossofAlzheimer’sdiseasebyactuallyencouragingneuronsinthebraintogrownewnerveextensions.PostmenopausalwomenwhodonothavehormonereplacementtherapyhaveagreaterchanceofdevelopingAlzheimer’sandmemorylossthanmenofthesameage,whosetestisterone[47]

ismetabolizedintoestradiol[48],aformofestrogen.

BreastCancer12.Muchofthecurrentresearchisfocusingonearlydetection.Studiesshowthatwomen

withamputation[49]ineithergeneBRCA1orgeneBRCA2haveasmuchasa56%chanceofdevelopingbreastcancerbyage70.Thepredictivepowerofthegenes,however,isstillbeingdebated,asscientiststrytodeterminehowgenes,environmentandotherfactorsaffectingtheappearanceandgrowthoftumors.Treatmentoptionsareconstantlyexpanding,thankstobetterunderstandingofhowbesttocombinesurgery,drugs,

chemotherapy[50]andradiation.Newformsofestrogenlikesupplements,initiallydevelopedtopreventosteoporosis[51],appeartopreventthegrowthofbreasttumorsaswell,

andmorecomprehensivestudiesshowthatanolddrug,tamoxifen[52],cancuttheriskofcancerasmuchas45%overfouryears.

DigestiveSystem13.Evenifamanandawomaneatthesamething,itmaytakethewomanmuchlongerto

digestit.Thatleaveswomenthreetimesasvulnerabletochronicconstipation[53]asmenandtwiceaslikelytodevelopintestinaldisorders.Thesexdiscrepancy[54]apparentlystartswithchewing:preliminarystudiesshowthatfemalesaliva[55]differschemicallyfromthatofmen,perhapssettingthestage[56]forfood’sslowerjourneythroughawoman’sdigestivesystem.

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CancerTypes14.TheProjectednumberofdeathsin1999:

   

    WOMEN1.Lung&bronchus[57] 680002.Breast 433003.Colon[58]&rectum[59] 288004.Pancreas[60] 147005.NonHodgkin’slymphoma[61] 14500    MEN1.Lung&bronchus 909002.Prostate[62] 370003.Colon&rectum 278004.Pancreas 139005.NonHodgkin’slymphoma 13400

FeelingPain15.Contrarytoanecdotalstories,numerousstudieshavedocumentedthatwomenexperiencepainmoreacutelyandmorefrequentlythanmen,indicatingthatthesexesmaydetectanddampenpaindifferently.Inastudyofdentalpatients,womenrespondedmorefavorablythanmentoaclassofpainrelieversknownaskappaopioids[63],includingpentazocine[64],suggestingthatreceptorsforinhibitingpainmayvarybysex.Moreover,womenarelessresponsivethanmentononsteroidal[65]antiinflammatory[66]drugs,

suchasibuprofen[67].

BoneLoss16.Women,morethanmen,experienceasignificantchangeintheirbonesinlaterlife.In

postmenopausalwomen,theskeletonbecomeslessdense,fullofperforations[68]causedbyosteoporosis.Thereasonforthedifference:lessestrogenaftermenopause.Thehormoneslowsdownbonelossandbuildsupboneaswell.Womenpastmenopausewhohaveestrogenreplacementtherapycanpreventasmuchas75%oftheirbonedegradationandcuttheirriskofahipfracture[69]50%.

 Notes

[1]exquisite[5ekskwizit]adj.优 美 的,

高雅的,精致的,剧烈的,异 常 的,细

腻的,敏锐的

[2]marauder[m[5rR:d[]n.掠夺者

[3]accommodate[[5kRm[deit]vt.供应,

供给,使适应,调节,和解,向……提

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供,容纳,调和

[4]fetus[5fi:t[s]n.胎儿

[5]lupus[5lu:p[s]n.狼疮

[6]rheumatoidarthritis[5ru:m[tRidB:

5Wraitis]n.类风湿关节炎

[7]multiplesclerosis[skli[5r[usis]n.多

发性硬化

[8]estrogen[5estr[dV[n]n.雌激素

[9]rev[rev]v.加快转速

[10]chestcrushingpain胸部压榨式疼痛

[11]hallmark[5hR:lmB:k]n.特点

[12]symptom[5simpt[m]n.症状,征兆

[13]postmenopausal[5p[Jst9men[J5pC:z[l]adj.(妇女)绝经后的,更年期的

[14]tradeoffn.交换,协定,交易,平衡

[15]churn[tF[:n]outv.艰苦地做出

[16]HDL高密度脂蛋白(highdensitylipo

protein)

[17]cholesterol[k[5lest[r[ul]n.胆固醇

[18]erratic[i5rAtik]heartbeats不 规 则 心

[19]hormonereplacementtherapy [5Wer[pi]激素替换治疗

[20]progestin[pr[u5dVestin]n.孕酮,黄

体酮

[21]diagnostic[7dai[g5nRstik]exam诊断

检查

[22]uterus[5ju:t[r[s]n.子宫(= womb)[23]ovary[5[uv[ri]n.[动 物]卵 巢,[植

物]子房

[24]cervix[5s[:viks]n.子宫颈

[25]Papsmearsn.定期进行乳突癌细胞抹

片检查(PapSmearTesting)

[26]malignant[m[5lign[nt]adj.恶性的

[27]cervical[5s[:vik[l]cancer子宫颈癌

[28]uterine[5ju:t[rain]adj.子宫的

[29]orthopedist[9R:W[u5pi:dist]n.整

形外科医师

[30]ligament[5li[m[nt]n.韧带

[31]tear[ti[]拉伤

[32]anteriorcrusiateligament[An5ti[ri[

5kru:sieit5li[m[nt]前十字韧带

[33]thigh[Wai]n.大腿,股

[34]feeltheeffects感到微醉

[35]aspirin[5Asp[rin]n.阿 斯 匹 林(解 热

镇痛药),乙酰水杨酸

[36]platelet[5peitlit]n.血小板

[37]betablockern.β受体阻滞药

[38]migraine[5maigrein]painn.偏头痛

[39]tricyclicantidepressant [trai5saiklik

7Antidi5pres[nt]三环类抗忧郁剂

[40]contraceptive[7kRntr[5septiv]adj.避孕的n.避孕品,避孕用具

[41]Pilln.避孕药

[42]serotonin[7si[r[5t[unin]n.5羟色胺

[43]norepinephrine[5nC:7repi5nefrin]n.去 甲 肾 上 腺 素 (epinephrine[7epi5nefrin]肾上腺素)

[44]adrenalgland[E5dri:nlglAnd]n.肾

上腺

[45]staveoff[steiv]v.避开,挡开,延迟

[46]dementia[di5menFi[]n.痴呆 (如senile[5si:nail]dementia老年性痴呆)

[47]testisterone[5testist[r[un]n.睾丸酮

[48]estradiol[7estr[5dai[ul]n.雌二醇

[49]amputation[7Ampju5teiF[n]n.切除,

切断手术

[50]chemotherapy[7kem[u5Wer[pi]n.化学疗法

[51]osteoporosis[7Rsti[upR:5r[Usis]n.骨质疏松症

[52]tamoxifen[t[5mRksifen]n.[药]三苯

氧胺,它莫西芬(一种抗雌激素,用于治

疗妇女乳腺癌或不育症)[53 ] chronic constipation [5krcnik

7kRnsti5peiF[n]n.慢性便秘

[54]discrepancy[dis5krep[nsi]n.差异

[55]saliva[s[5laiv[]n.口水,唾液

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[56]setthestagefor:为……打 好 基 础;

为……创造条件

[57]bronchus[5brRNk[s]n.支气管

[58]colon[k[u5l[u]colonsn.结肠

[59]rectum[5rekt[m]n.直肠

[60]pancreas[5pANkri[s]n.胰腺

[61]NonHodgkin’slymphoma[lim5f[um[]非霍奇金淋巴瘤

[62]prostate[5prCsteit]n.前列腺

[63]opioid[5[UpjRid]n.鸦片类物

[64]pentazocine[pen5tAz[si:n]n.[药]戊

唑辛,镇痛新(代替吗啡的合成镇痛药,

不易上瘾)[65]nonsteroidal[nRn5sti[rRid]adj.非

类固醇的

[66] antiinflammatory drug [5Antiin5flAm[t[ridrQg]n.抗炎药

[67]ibuprofen[9aibjJ5pr[Jfin]n.[药]异

丁苯丙酸,布洛芬(抗炎、镇痛药)[68]perforation[p…f[5reiF[n]n.穿孔

[69]hipfracture[hip5frAktF[]n.臀部骨

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犝犖犐犜07 犕犐犆犚犗犅犈犛

犈狊狊犪狔21 犃犵狉狅犫犪犮狋犲狉犻狌犿狋狌犿犲犳犪犮犻犲狀狊犪狀犱犐狋狊犝狊犲狊犻狀犘犾犪狀狋犅狉犲犲犱犻狀犵

1.Agrobacteriumtumefaciens[1]causescrowngall[2]diseaseofawiderangeofdicotyledonous(broadleaved)plants,especiallymembersoftherosefamily[3]suchasapple,

pear,peach,cherry,almond,raspberry[4]androses.Aseparatestrain[5],termedbiovar[6]3,causescrowngallofgrapevine[7].

2.Thediseasegainsitsnamefromthelargetumourlikeswellings(galls)thattypicallyoccuratthecrownoftheplant,justabovesoillevel.Althoughitreducesthemarketability[8]ofnurserystock[9],itusuallydoesnotcauseseriousdamagetoolderplants.Nevertheless,thisdiseaseisoneofthemostwidelyknown,becauseofitsremarkablebiology.Basically,thebacteriumtransferspartofitsDNAtotheplant,andthisDNAintegrates[10]intotheplant’sgenome,causingtheproductionoftumoursandassociatedchangesinplantmetabolism.

3.TheuniquemodeofactionofA.tumefacienshasenabledthisbacteriumtobeusedasatoolinplantbreeding.Anydesiredgenes,suchasinsecticidaltoxingenesorherbicideresistancegenes,canbeengineeredintothebacterialDNAandtherebyinsertedintothe

plantgenome.TheuseofAgrobacterium notonlyshortenstheconventionalplantbreedingprocess,butalsoallowsentirelynew(nonplant)genestobeengineeredintocrops.

4.ThestoryofAgrobacteriumgoesevenfurtherthanthis,makingitoneofthemostinterestingandsignificantbacteriafordetailedstudy.Forexample,thereisahighlyeffectivebiologicalcontrolsystemforthisdisease—oneofthefirstandmostsuccessfulexamplesofbiologicalcontrolofplantdisease.

5.Hereweconsiderthreemajoraspectsofthisintriguing[11]disease:thebiologyofthebacteriumandtheinfectionprocess,thedevelopmentofahighlysuccessfulbiologicalcontrolsystemagainstcrowngalldisease,thewideruseofA.tumefaciensasatoolforgeneticengineeringofplants.

Thebacteriumanditsplasmids6.A.tumefaciensisaGramnegative[12],nonsporing,motile,rodshapedbacterium,

closelyrelatedtoRhizobium[13]whichformsnitrogenfixingnodules[14]onclover[15]andotherleguminous[16]plants.StrainsofAgrobacteriumareclassifiedinthreebiovars

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basedontheirutilizationofdifferentcarbohydratesandotherbiochemicaltests.ThedifferencesbetweenbiovarsaredeterminedbygenesonthesinglecircleofchromosomalDNA.Biovardifferencesarenotparticularlyrelevanttothepathogenicity[17]ofA.tumefaciens,exceptinonerespect:biovar3isfoundworldwideasthepathogenofgrapevines.Butthisisalmostcertainlybecausebiovar3hasbeenspreadaroundtheworldinvegetativecuttings[18]ofvines,notbynaturalmechanisms.

7.MostofthegenesinvolvedincrowngalldiseasearenotborneonthechromosomeofA.tumefaciensbutonalargeplasmid,termedtheTi(tumourinducing)plasmid[19].Inthesameway,mostofthegenesthatenableRhizobiumstrainstoproducenitrogenfixingnodulesarecontainedonalargeplasmidtermedtheSym (symbiotic[20])plasmid.Thus,thecharacteristicbiologyofthesetwobacteriaisafunctionmainlyoftheirplasmids,notofthebacterialchromosome.(AplasmidisacircleofDNAseparatefromthechromosome,capableofreplicatingindependentlyinthecellandofbeingtransferredfromonebacterialcelltoanotherbyconjugation[21].Plasmidsencodenonessential[22]

functions,inthesensethatabacteriumcangrownormallyincultureeveniftheplasmidislost.)

8.Thecentralroleofplasmidsinthesebacteriacanbeshowneasilyby“curing”[23]ofstrains.Ifthebacteriumisgrownnearitsmaximumtemperature(about30℃inthecaseofAgrobacteriumorRhizobium)thentheplasmidislostandpathogenicity(ofAgrobacterium)ornoduleformingability(ofRhizobium)alsoislost.However,lossoftheplasmiddoesnotaffectbacterialgrowthinculture—theplasmidfreestrainsareentirelyfunctionalbacteria.

9.InlaboratoryconditionsitisalsopossibletocureAgrobacteriumorRhizobiumandthenintroducetheplasmidoftheotherorganism.IntroductionoftheTiplasmidintoRhizobiumcausesthistoformgalls;introductionoftheSymplasmidintoAgrobacteriumcausesittoformnodulelikestructures,althoughtheyarenotfullyfunctional.

10.Studiessuchastheseraisemanyinterestingandchallengingquestionsaboutthenatureofbacteria.Forexample,whatdoesthenameofabacterialspeciesorgenus[24]reallymean,iftheorganismcanchangesodrasticallybylossorgainofanonessentialplasmid?Andhowmuchgeneexchangeoccursbymeansofplasmidsandothermobilegeneticelements[25]withinnaturalpopulations?

Theinfectionprocess11.Agrobacteriumtumefaciensisfoundcommonlyonandaroundrootsurfaces—there

giontermedtherhizosphere[26]— whereitseemstosurvivebyusingnutrientsthatleakfromtheroottissues.Butitinfectsonlythroughwoundsites,eithernaturallyoccurringorcausedbytransplantingofseedlingsandnurserystock.Thisrequirementforwoundscanbedemonstratedeasilyinlaboratoryconditions.Forexample,tothebasesoftwoyoungtomatoplants,adropofA.tumefaciensbacterialsuspensionwasplacedonthestemandapinprick[27]wasthenmadeintothestematthispoint.Fiveweekslater,the

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younggallsdevelopedfromthemeristematic[28]tissuesaroundthecentralvascularsystem.

12.Innaturalconditions,themotilecellsofA.tumefaciensareattractedtowoundsitesbychemotaxis[29].Thisispartlyaresponsetothereleaseofsugarsandothercommonrootcomponents,anditisfoundeveninplasmidcuredstrains.However,strainsthatcontaintheTiplasmidrespondevenmorestrongly,becausetheyrecognizewoundphenolic[30]compoundssuchasacetosyringone[31]whicharestronglyattractiveatevenverylowconcentrations(10-7Molar).Thus,oneofthefunctionsoftheTiplasmidistocodeforadditional,specificchemotacticreceptors[32]thatareinsertedinthebacterialmembraneandenablethebacteriumtorecognizewoundsites.

13.Acetosyringoneplaysafurtherroleintheinfectionprocess,becauseathigherconcentrations(about10-5to10-4 Molar)thanthosethatcausechemotaxisitactivates[33]thevirulencegenes[34](Virgenes)ontheTiplasmid.Thesegenescoordinatetheinfectionprocessand,inparticular:leadtotheproductionofproteins(permeases[35])thatareinsertedinthebacterialcellmembraneforuptakeofcompounds(opines[36])thatwillbeproducedbythetumours;causetheproductionofanendonuclease[37]—arestrictionenzyme[38]—thatexcisespartoftheTiplasmidtermedtheTDNA(transferredDNA).

14.TheexcisedTDNAisreleasedbythebacteriumandenterstheplantcells,whereitintegratesintotheplantchromosomesanddictates[39]thefunctioningofthosecells.Theactualmechanismoftransferisstillunclear,butitseemstorequireaconditioningprocess[40],perhapsmediated[41]bytheproductionofcytokinins[42](planthormones)bythebacterium.Thetzs(transzeatin[43])geneontheTiplasmidcodesforthehormone.

 Notes

[1 ] Agrobacterium tumefaciens[9AgrEbAk5ti[ri[m 9tju:

mi5feiF[ns]n.根癌农杆菌

[2]crowngall[kraUngC:l]n.冠瘿病

[3]rosefamilyn.蔷薇科

[4]strain[strein]n.菌株

[5]raspberry[5rB:zb[ri]n.悬钩子

[6]biovar[bai5[uvB:]n.生物型

[7]grapevine[5greipvain]n.葡萄藤,葡萄

[8]marketabilityn.可销售性

[9]nurserystockn.苗木,定植苗,出圃

[10]integratev.整合

[11]intriguingadj.迷人的,有迷惑力的,引起兴趣(或好奇心)的

[12]Gramnegativeadj.革兰氏阴性的

[13]Rhizobiumn.根瘤菌

[14]nodule[5nRdjU:l]n.小结,小瘤

[15]clover[5kl[Uv[]n.三叶草,苜蓿

[16]leguminous[le5gju:min[s]adj.豆科的

[17]pathogenicity[7pAW[dVi5nisiti]n.病原性,致病性

[18]vegetative[5vedVit[tiv]cuttingn.营

养切条

[19]Ti(tumourinducing)plasmid[5plAzmid]n.肿瘤诱导质粒

[20]symbiotic[7simbai5Ctik]adj.共生的

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[21]conjugation[9kCndVu5geiF[n]n.结

[22]essential[i5senF[l]adj.必需的

[23]curev.治 愈,治 疗,此 处 指“质 粒 消

除”[24]genus[5dVi:n[s]n.(生物分类)属[25]mobilegeneticelementn.可 移 动 遗 传

因子(转座子)[26]rhizosphere[5raiz[9sfi[]n.根围(指

围绕植物根系在土壤中的一个区域)[27]pinprick针刺

[28]meristematic[7merist[5mAtik]adj.分生组织的

[29]chemotaxis[9kem[5tAksis]n.[动

物]化学 向 性,[生 物]趋 化 现 象,趋 药

[30]phenolic[fi5nClik]adj.酚类的

[31]acetosyringone[eisit[u5si[riNgC:n]

n.乙酰丁香酮

[32]chemotactic[9kem[u5tAktik]receptorn.向化性受体

[33]activate[5Aktiveit]v.激活

[34]virulence[5vrul[ns]genen.毒 力 基

[35]permease[5p…mieis]n.透过酶

[36]opine[[u5pain]冠瘿碱

[37]endonuclease[7end[5nju:kli7eis]n.内切酶

[38]restrictionenzymen.限 制 性 内 切 酶,限制酶

[39]dictatev.指令,指示,命令,规定

[40]conditioningprocessn.条件作用过程

[41]mediate[5mi:diit]v.作 为 引 起……的媒介,介导

[42]cytokinin[5sait[5kinin]n.细 胞 分 裂

[43]tzs(transzeatin)[trAns5zi:[tin]n.反式玉米素

犈狊狊犪狔22 犅犪犮犻犾犾狌狊狋犺狌狉犻狀犵犻犲狀狊犻狊犪狀犱犐狋狊犝狊犲狊

1.Bacillusthuringiensis[1](commonlyknownasBt)isaninsecticidal[2]bacterium,marketedworldwideforcontrolofmanyimportantplantpests— mainlycaterpillarsoftheLepidoptera[3](butterfliesandmoths)butalsomosquitolarvae[4],andsimuliidblackflies[5]thatvector[6]riverblindnessinAfrica.Btproductsrepresentabout1%ofthetotal‘agrochemical’market(fungicides[7],herbicides[8]andinsecticides[9])acrosstheworld.ThecommercialBtproductsarepowderscontainingamixtureofdriedsporesandtoxincrystals.Theyareappliedtoleavesorotherenvironmentswheretheinsectlarvaefeed.Thetoxingeneshavealsobeengeneticallyengineeredintoseveralcropplants.Themethodofuse,modeofaction,andhostrange[10]ofthisbiocontrola

gent[11]differmarkedlyfromthoseofBacilluspopilliae[12].

Modeofaction2.Thecrystalsareaggregates[13]ofalargeprotein(about130~140kDa[14])thatisactuallyaprotoxin[15]—itmustbeactivatedbeforeithasanyeffect.Thecrystalproteinishighlyinsolubleinnormalconditions,soitisentirelysafetohumans,higheranimalsandmostinsects.However,itissolubilizedinreducingconditionsofhighpH(abovea

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boutpH9.5)—theconditionscommonlyfoundinthemidgut[16]oflepidopteranlarvae.Forthisreason,Btisahighlyspecificinsecticidalagent.

3.Onceithasbeensolubilizedintheinsectgut,theprotoxiniscleavedbyagutprotease[17]toproduceanactivetoxinofabout60kD.Thistoxinistermeddeltaendotoxin[18].Itbindstothemidgutepithelialcells[19],creatingporesinthecellmembranesandleadingtoequilibrationofions.Asaresult,thegutisrapidlyimmobilized[20],theepithelialcellslyse[21],thelarvastopsfeeding,andthegutpHisloweredbyequilibrationwiththebloodpH.ThislowerpHenablesthebacterialsporestogerminate,andthebacteriumcantheninvadethehost,causingalethalsepticaemia[22].

4.Recentstudiesonthedeltaendotoxinstructureshowthatithasthreedomains[23].DomainIisabundleof7alphahelices,someorallofwhichcaninsertintothegutcellmembrane,creatingaporethroughwhichionscanpassfreely.DomainIIconsistsofthreeantiparallelbetasheets[24],similartotheantigenbindingregions[25]ofimmuno

globulins[26],suggestingthatthisdomainbindstoreceptorsinthegut.DomainIIIisatightlypackedbetasandwich[27]whichisthoughttoprotecttheexposedend(Cterminus[28])oftheactivetoxin,preventingfurthercleavagebygutproteases.Interestingly,

thediphtheriatoxin[29](ofanotherbacterium)hasanessentiallysimilarstructuretotheBttoxin.

History,productsandinsecthostrange5.Bacillusthuringiensiswasfirstdiscoveredin1911asapathogenofflourmoths[30]fromtheprovinceofThuringia[31],Germany.ItwasfirstusedasacommercialinsecticideinFrancein1938,andthenintheUSAinthe1950s.However,theseearlyproductswerereplacedbymoreeffectiveonesinthe1960s,whenvarioushighlypathogenicstrainswerediscoveredwithparticularactivityagainstdifferenttypesofinsect.

6.Formanyyears,Btwasavailableonlyforcontroloflepidoptera,usingahighlypotent[32]strain(B.thuringiensisvarkurstaki[33]).ThisstrainstillformsthebasisofmanyBtformulations[34].Furtherscreening[35]ofalargenumberofotherBtstrainsrevealedsomethatareactiveagainstlarvaeofcoleopteran[36](beetles)ordiptera[37](smallflies,mosquitoes).Mostofthesestrainshavethesamebasictoxinstructure,butdifferininsecthostrange,perhapsbecauseofdifferentdegreesofbindingaffinitytothetoxinreceptorsintheinsectgut.Forexample,thetoxinsproducedbyB.thuringiensisvaraizawai[38]havesomewhatdifferenttoxinsfromthoseofBt.varkurstakiandtheyarehighlyspecifictolepidoptera,withnoeffectonotherinsects.ThemanycommercialstrainsforcontroloflepidopteraaremarketedundervarioustradenamessuchasBiobit?,Dipel?,Javelin?,etc.

7.Incontrast,thetoxinsproducedbystrainsofB.t.varisraelensis[39]arehighlyactiveagainstsimuliidblackfly,vectorsofsometropicaldiseases,andalsoagainstfungusgnat[40]larvaeandsometypesofmosquito(especiallyAedes[41]species,buthighertoxindosesareneededforcontrolofCulexspp[42].andAnophelesspp[43].).Tradenamesfor

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theseproductsincludeSkeetal?,Vectobac?andMosquitoAttack?.8.StrainsofB.t.varsandiego[44]orB.t.vartenebrionis[45]aremarketedforcontrolofsomecoleoptera—especiallyforcontroloftheimportantColoradopotatobeetle[46].

Bttoxinsandtheirclassification9.B.thuringiensisstrainsproducetwotypesoftoxin.ThemaintypesaretheCry(crystal)toxins[47],encodedbydifferentcrygenes,andthisishowdifferenttypesofBtareclassified.ThesecondtypesaretheCyt(cytolytic)toxins[48],whichcanaugment[49]

theCrytoxins,enhancingtheeffectivenessofinsectcontrol.Over50ofthegenesthatencodetheCrytoxinshavenowbeensequencedandenablethetoxinstobeassignedtomorethan15groupsonthebasisofsequencesimilarities[50].Thetablebelowshowsthestateofsuchaclassificationin1995,butanalternativeclassificationhasrecentlybeenproposed.

Gene Crystalshape Proteinsize(kDa) Insectactivity

cryⅠ[severalsubgroups:

A(a),A(b),A(c),B,C,D,E,F,G]bipyramidal[51] 130~138 lepidopteralarvae

cryⅡ [subgroupsA,B,C] cuboidal[52] 69~71 lepidopteraanddiptera

cryⅢ [subgroupsA,B,C] flat/irregular 73~74 coleoptera

cryⅣ [subgroupsA,B,C,D] bipyramidal 73~134 diptera

cryⅤ~Ⅸ various 35~129 various

Recentapproachestostraindevelopment10.Ithasbeenknownsincethe1980sthattheCrytoxinsareencodedbygenesonplasmids

ofB.thuringiensis.Therecanbe5or6differentplasmidsinasingleBtstrain,andtheseplasmidscanencodedifferenttoxingenes.TheplasmidscanbeexchangedbetweenBtstrainsbyaconjugationlikeprocess,sothereisapotentiallywidevarietyofstrainswithdifferentcombinationsofCrytoxins.Inadditiontothis,Btcontainstransposons[53](transposablegeneticelementsthatflank[54]genesandthatcanbeexcisedfromonepartofthegenomeandinsertedelsewhere).AllthesepropertiesincreasethevarietyoftoxinsproducednaturallybyBtstrains,andprovidethebasisforcommercialcompaniestocreategeneticallyengineeredstrainswithnoveltoxincombinations.OneofthefirstsuchproductswasaBtstrainmarketedasRaven?forenhancedcontrolofColoradopotatobeetleaswellasforcaterpillarsthatattackpotato,tomatoandauber

gine[55]plants(allofwhichareinthesameplantfamily— Solanaceae[56]).ThisBtstraincontainedtwodifferentbeetleactiveCryIIIproteins(withdifferentbindingaffinitiesformidgutcellmembranesofColoradobeetle)aswellastwocaterpillaractiveCryIproteins.Suchanapproach—oftentermedgenepyramiding[57]—isdesignedtodelaythedevelopmentofresistanceintargetpests,becauseresistancewouldhavetode

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velopsimultaneouslytoseveraldifferenttoxins.11.Suchresistancecandevelopquiterapidlywhenonlyonetypeoftoxinisinvolved.Infact,ithappenedwithin1or2yearswhenthemosquitoactiveBtstrainswerewidelyusedintropicalcountries.Thebasisofresistanceseemstobecomplex,involvingseveralfactors.Butoneencouraging[58]findingisthat,atleastinsomeinsects,thereceptorfortheBttoxinisanessentialgutenzyme,anaminopeptidase[59],soanychangeinthisreceptorthatcausesalossofbindingtothetoxincouldalsobedetrimentaltotheinsect,

potentiallyreducingthefitnessoftheresistantinsects.

PlantsgeneticallyengineeredwiththeBtgene12.Since1996,awiderangeofcropplantshavebeengeneticallyengineeredtocontainthe

deltaendotoxingenefromBacillusthuringiensis.These“Btcrops”arenowavailablecommerciallyintheUSA.Theyinclude“Btcorn”,“Btpotato”,“Btcotton”and“Btsoybean”.SuchplantshavebeengeneticallyengineeredtoexpresspartoftheactiveCrytoxinintheirtissues,sotheykillinsectsthatfeedonthecrops.

13.Insomerespects,thisisanimportanttechnologicalandpracticaldevelopment,becauseitensuresthatonlythoseinsectsthatattackthecropwillbeexposedtoBttoxins—

thereisnorisktoothertypesofinsect.ItalsoensuresthattherangeofusesforBtisextendedtoinsectsthatfeedontherootsorthatbore[60]intotheplanttissues—forexample,theEuropeancornborer[61]— becausesuchinsectscannotbecontrolledbyBtsuspensionssprayedontoplantsurfaces.

14.However,thereisalsoa“downside[62]”,becausethetargetinsectsareperpetuallyexposedtotoxinsandthiscreatesaverystrongselectionpressure[63]forthedevelopmentofresistancetothetoxins.Variouscropmanagementstrategiesarebeingdevelopedtotrytominimizethisrisk.

 Notes

[1]B.thuringiensis(Bt)[b[5sil[sWjJ[rindVinsis]n.苏云金杆菌

[2]insecticidal[in9sekti5said[l]adj.杀

昆虫的,杀昆虫剂的

[3]lepidoptera[9lepi5dCpt[r[]n.鳞 翅

[4]mosquitolarvae[m[s5ki:t[u5lB:v[]

n.蚊子幼虫

[5]simuliid[si5mju:lid]blackfly蚋黑蝇

[6]vector[5vekt[]v.向……带菌

[7]fungicide[5fQndVisaid]n.杀真菌剂

[8]herbicide[5h[:bisaid]n.除草剂

[9]insecticide[in9sekti5said]n.杀 昆 虫

[10]biocontrolagentn.生物防治剂

[11]hostrangen.宿主范围

[12]Bacilluspopilliaen.(日本)金龟子芽

孢杆菌

[13]aggregate[5Agrigeit]n.聚合体

[14]kDan.(分 子 量 单 位)千 道 尔 顿(kilodalton)

[15]protoxin[pr[u5tRksin]n.原毒素

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[16]midgutn.(昆虫)中肠

[17]protease[5pr[utieis]n.蛋白酶

[18]deltaendotoxin[7end[u5tRksin]n.德耳塔内毒素

[19]epithelial[7epi5Wi:lj[l]celln.上皮细

[20]immobilize[i5m[Jbilaiz]v.固定

[21]lyse[lais]v.细胞裂解

[22]septicaemia[septi5kAmi[]n.败血病

[23]domain[d[u5mein]n.结构域

[24]betasheetn.beta(折叠)片层

[25]antigenbindingregionn.抗原结合区

[26 ] immunoglobulin [i5mju: n[U5glCbjulin]n.免 疫 球 蛋 白(即 抗

体)[27]betasandwichn.beta(折 叠)片 层 构

成的夹心

[28]Cterminusn.C末端,羧基末端

[29]diphtheria[dif5Wi[ri[]toxinn.白 喉

毒素

[30]flourmothn.面粉蛾

[31]Thuringia[WjJ[rindVi[]n.图林根州

[德意志联邦共和国州名][32]potent[5p[Ut[nt]adj.强力的,有力

的,有效的

[33]B.thuringiensisvarkurstaki苏 云 金

杆菌库斯塔变种

[34]formulation[7fC:mju:leiF[n]n.配

[35]screen[skri:n]v.筛选

[36]coleopteran[7kCli5Rpt[r[n]n.鞘 翅

[37]diptera[dip5t[r[]n.双翅类

[38]B.thuringiensisvaraizawai苏 云 金

杆菌鲇泽变种

[39]B.t.varisraelensis苏云金杆菌以色列

变种

[40]gnat[nAt]n.小 昆 虫。fungusgnats(蕈蚊):小 型 双 翅 蝇 构 成 蕈 蚊 科 和 尖

眼蕈蚊科任何一种,具有取食真菌的幼

虫。[41]Aedes[ei5idi:z]n.伊 蚊(一 种 传 染 黄

热病的蚊子)[42]Culexspp.[5kju:lek5sQbspi:Fi:z]

库蚊亚种 (常见于北美、欧洲)[43]Anophelesspp.[E5nCfili:z5sQbspi:

Fi:z]按蚊亚种

[44]B.t.varsandiegon.苏云金杆菌圣地

牙哥变种

[45]B.t.vartenebrionisn.苏 云 金 芽 孢 杆

菌拟步行甲变种

[46]Coloradopotatobeetlen.科罗拉多薯

[47]Cry(crystal)toxinn.晶体毒素

[48]Cyt(cytolytic)toxinn.细胞裂解毒素

[49]augment[C:g5ment]v.增加,增大

[50]sequencesimilarityn.序列相似性

[51]bipyramidal[7bai5pir[mid[l]adj.双

棱锥的

[52]cuboidal[kju:5bCid[l]adj.立方形的

[53]transposon[trAns5p[usRn]n.转 座

[54]flankvt.在……的侧面,侧翼包围,守

侧面

[55]aubergine[7[ub[5Vi:n]n.茄子,(茄

子般的)紫红色

[56]Solanaceaen.茄科

[57]genepyramidingn.基因聚合。就是将

分散在不 同 品 种 中 的 优 良 性 状 基 因 通

过杂交、回 交、复 合 杂 交 等 手 段 聚 合 到

同一个品种中。[58]encouragingadj.令人鼓舞的

[59]aminopeptidase[[7min[5peptideis]n.氨基肽酶

[60]bore[bR:]v.钻

[61]Europeancornborern.欧洲玉米钻心

[62]downsiden.底侧,下降趋势

[63]selectionpressuren.选择压力

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犈狊狊犪狔23 犛狅犿犲犉犪犮狋狊犃犫狅狌狋犈.犮狅犾犻

WhatdoesthetermE.colimean?

1.E.coli[1]istheabbreviationforthebacteriumintheFamilyEnterobacteriaceae[2]namedEscherichia(Genus)coli(Species)[3].Approximately0.1%ofthetotalbacteriawithinanadult’sintestines(onaWesterndiet)isrepresentedbyE.coli.Butanewborninfant’sintestineshaveE.coli,alongwithlactobacilli[4]andenterococci[5]asthemostabundantbacterialflora[6].2.Itisforthisreasonthattheorganismswhichhappilyinhabittheintestinaltractasnormalfloraarenamedenteric[7]bacteria.TheFamilytowhichE.colibelongs(Enterobacteriaceae)

isnamedwhatitis—becauseoftheGreekwordenterikos—whichpertainstotheintestineandthenameofthepersonwhofirstisolatedandcharacterizedthisbacterium,Escherich.

AreE.colibacteriaSAFE?

3.Yes,mostly.ThepresenceofE.coliandotherkindsofbacteriawithinourintestinesisnecessaryforustodevelopandoperateproperly,andforustoremainhealthy—E.coli,alongwithotherspeciesofbacteria,providesuswithmanynecessaryvitamins.Bacteriamakethevitamins,andweabsorbthem.WedependuponE.coliinourintestinesasoursourceofVitaminKandBcomplexvitamins.4.Thefetusofanyanimaliscompletelysterile.Immediatelyafterbirth,thenewbornsacquireallkindsofdifferentbacteriawhichlivesymbioticallywiththenewbornsandthroughouttheirlife.Fromthedayweareborn,wehavebacteria.Thehelpfulbacteriaarelocated“only”inregionsofourbodydirectlyexposedtotheenvironment(ourintestines,upperandlowerrespiratorytract[8],etc)andneverinourbloodstreamortheinsidetissuesourbody.Animalsthatarebornandraised“germfree”[9]arereallyquiteunhealthy,theyhavethinintestinalwalls,puny[10]hearts,andrequirelotsofvitaminsupplementstoexist.

WhenareE.colibacteriaNOTSAFE?

5.Somebacteriaarenotverynice.WecallsuchindividualE.colibacteriaadifferent“strain”ofbacteriawithinagivenspecies.Someofthesedifferentstrains(andtheremaybeseveralwithinagivenspecies)canbeharmfultous.TheseindividualstrainsofE.coliexist!ThismeansthatthisparticularindividualstrainofE.coliisgeneticallydifferentthanthevastmajorityofE.coliinourintestines.IfthisE.colistrainhappenstohavegeneticinformationforproducingharmfulbyproducttous,weareintrouble.

WhichE.coliareBAD?

6.TherarestrainofE.colithatisBADforusisE.coliO157:H7,amemberoftheEHEC

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—enterohemorrhagic[11]E.coligroup.ThetermEnterohemorrhagicmeansanintestinallyrelatedorganismwhichcauseshemorrhaging[12],i.e.,lossofblood.

Howdowepickupthisstrain?

7.E.colibacteriaareeverywhereintheenvironment.Theyareacommonoccupantofallanimals.Anytimeweeatsomething,drinksomething,ortouchourhandstosomethingthathasbeeneitherapartoforhasbeennearwhereanimalsare,thereisalwaysthepotentialtoingestthesebacteria.

WheredoesthisstrainofE.colicomefrom?

8.Bacterialcellsareallovertheplaceanditispossibleforthemtoacquiregeneticinformationfromothersources(bacterialviruses,plasmids,orfrompiecesofDNA).Insomecases,acquisitionofthisinformationmayprovideanadvantageforsurvival.ButE.coliO157:

H7appearstohavebeeninfectedwithabacterialvirusthathadtheabilitytoinsertitsownDNAintothebacteria’schromosomewithoutharmingthebacterium.Everytimethisbacterialcelldivided,thevirusDNA,beingnowapartofthebacterialDNA,waspassedontoeverydaughtercell—creatingtheE.colistrain,O157:H7.Thisvirus’sgeneticinformation(genes)containedinformationfortheproductionofatoxin,calledShigaliketoxin(SLT)[13],sometimescalled,Verotoxin.Consequently,thisstrainofE.coli,andallofitsprogenyproducedthistoxin.Thistoxinisaproteinwhichcausesseveredamagetointestinalepithelialcells.Welosewaterandsalts;bloodvesselsaredamagedandbleedingoccurs—

hemorrhaging,aconditionparticularlydangeroustosmallchildren—evenlethal.Childrenaretoosmalltotolerateverymuchbloodandfluidloss.Forthisreason,smallchildrenshouldnotbeallowedtobecomedehydrated,eveninmildcasesofdiarrhea[14].Insomecases,anothersyndromeisinvolvedwhichiscalledhemolyticuremicsyndrome(HUS)[15],

characterizedbykidneyfailureandlossofredbloodcells.Approximately5%to10% ofsmallchildrenprogresstothisstageofthedisease—whichisextremelydangeroustothem.Inseverecases,permanentkidneydamageoccurs.Thisbacteriumcanalsobeverydangeroustotheelderlyorinfirm[16].TherecanbeacombinationofHUSandotherthingswhichinvolvethebloodsystem.Thiscanbelethaltotheelderlyin50%ofthecases.

 Notes

[1]E.coli[i5k[ulai]n.大肠杆菌

[2]Enterobacteriaceae[7ent[r[u5bAkti[rieisi[]n.肠细菌科

[3]Escherichia(Genus)coli(Species)埃

希氏菌属大肠杆菌

[4]lactobacillus[7lAkt[ub[5sil[s]n.乳

酸杆 菌;lactobacilli(pl)[7lAkt[ub[si5lai]

[5]enterococcus[7ent[r[u5kRk[s]n.肠

球 菌;enterococci (pl) [7ent [r

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[u5kRsai][6]bacterialflora[bAk5ti[ri[l5flR:r[]

n.细菌群

[7]enteric[en5terik]bacterian.肠细菌

[8]upperandlowerrespiratory[ris5pai[r[t[ri]tractn.上、下呼吸道

[9]germfreeadj.无菌的;adv.无菌

[10]puny[5pju:ni]adj.小 的,弱 的,微

不足道的

[11]enterohemorrhagic [7ent[r[u5hem

[ridVik]adj.肠出血的

[12]hemorrhage[5hem[ridV]n.出血

[13]Shigaliketoxin(SLT)类 志 贺 毒 素

(有时称Vero毒素)[14]diarrhea[7dai[5ri[]n.痢疾,腹泻

[15]hemolyticuremicsyndrome (HUS)[hi:m[u5litik5jur[mik5sindr[um]n.溶血性尿毒症

[16]theinfirmn.体弱多病者

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犝犖犐犜08 犃犖犐犕犃犔犅犈犎犃犞犐犗犚

犈狊狊犪狔24 犜犺犲犈犾犲狆犺犪狀狋

1.Everythingabouttheelephantisspectacular.Gestation[1]inthefemaleelephanttakesnearlytwentyonemonths.AmaleAfricanelephantcanweighasseventonsandstandelevenfeetattheshoulder.Althoughtheaverageisless,theIndianspecieshasbeenknowntoreachsixtonsandstandnearlytenfeet.Yetinspiteoftheirsize,bothcanmoveassilentlyasashadowontheirgreatcushioned[2]feetwhentheyneedto.Althoughelephantscansometimesbeverynoisyanimals,tearingdownleavesfromtreesorsquealing[3]whentheyareafraid,theyhaveanalmostfrighteningabilitytodisap

pear.2.Nothingcouldbetterillustratethecontradictionsofnaturethanthefactthatforallthe

powerandstrengthofitsgiantsize,theelephantcannotrunintherealsenseoftheword,asforexampleahorsedoes.Normallyitmovesataboutsixmilesanhour,whilewhenitcharges[4](torushasifinanattack)itdoessoatprobablynomorethantwentymilesanhour,althoughbecauseofitssizeanditsobviousangerachargingelephantisanexperiencenoteasilytobeforgotten.Again,theelephantcannotjump;itcanonlystepacoupleofyardsatatime,whichmakescompletelyeffectivetheapparentlyrathersmallelephanttrenches[5]sometimesdugtoprotecthouses.

3.Asforthosespectaculartusks[6],whichhavesooftenbeenthecurseoftheelephant,

thoseoftheAfricanmaleareoftenmorethansixfeetinlength,lessinthefemale.TheheaviesttuskeverrecordedinAfricaweighed225pounds,whilethegreatestlengthwasnearlyelevenfeetsixinches.

4.InthemaleIndianelephant,tusksarerarelymorethanthreeorfourfeetinlength,

whilethefemaleIndianelephanthasnotusks.AconsiderablenumberofIndianmalesarealsotuskless.Theyareknownas makhnas,beingcompensatedbyimmensestrengthparticularlyinthehead,neckandtrunk[7],anditisquitecommonforatusklessmaletocontrolaherd.

5.Wheretheyexist,thosegreattuskscanbeusedformanypurposes,bothastoolsandweapons.Theycanbeusedtodigupdeliciousrootsormovebranchestoclearthewayforthetrunk.Andwhenthereisnobranchnearby,anelephantwillrestitstrunkononeofitstusks.

6.Itusedtobethoughtimpossibletodomesticate[8]theAfricanelephant,butthisisnot

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so,considerablenumbersbeingtrainedforworkintheonetimeBelgianCongo,nowZaire[9].However,itiswithIndiaandnearbyAsiancountriessuchasBurmaandThailandthatelephantsasforestworkersareusuallyassociated.

7.ThemostcommonmethodofcaptureinIndiaistheancientpittrap[10].Thedisadvantagesofthisarethepossibilityofotheranimals,suchastheIndianbuffalo[11],beingcaught,andalsothepossibilityofanelephantsufferinginjurywhenfallingintothepit,

eventhoughthisneedbeonlyafewfeetdeepowingtotheelephantsinabilitytojumporstepmorethanacoupleofpaces.Butwhatevertheadvantagesordisadvantagesofpitfalltraps,theirconstruction,locationandthewaytheyarehiddenareexcellentexamplesoftheskillandknowledgeofthehunters.InCoorg[12]andMysore[13]thetrappingiscarriedoutbyCorubas[14],membersofoneofthevanishingtribesofIndia.Nowelephants,intheirsearchforfoodandwater,travelgreatdistances,manymiles,alongtheirownspecialtrailsorroads,manydaysorweekssometimespassingbeforetheycomethesamewayagain.AtcarefullyconsideredplacestheCorubasdigtheirpits,

coveringthemoverwithbranchesandleavesandgrassinsuchawaythatunlessoneknowsoftheirexistenceitisimpossibletodistinguishthemformthesurroundingearth.

8.Theidealcaptureisayoungelephantofaroundnineortenyearsofage,becauseitismucheasiertotrain.Bringingacaptivetothesurfaceisasurprisinglysimpleprocess.Afterithasbeentiedwithropetoacoupleofcampelephants[15](withathirdinreserve)standingclosetothepit,thetribesmenbegintofillthepitwithbranchescutfromthesurroundingjungle.Initsangerthecaptivetramples[16]allthisdown,withtheresultthatitisslowlyraisedtogroundlevel.

9.Althoughatfirstsightitwillprobablybeveryviolentanddifficulttohandle,afterthreeweeksitwillbetakingitsfirstlessons,andintimeitwillbeabletodoeverythingtheothercampelephantscando.Itisstrangethatthelargestandmostspectacularlandanimalshouldbesuchanobedientservanttoacreatureitcouldkillwithaslightmovementofitstrunk.

 Notes

[1]gestation[dVes5teiF[n]n.怀 孕,孕

育时期,酝酿

[2]cushioned[5kuF[nd]adj.有 软 垫 子

[3]squeal[skwi:l]v.长声尖叫

[4]charge[tFB:dV]v.冲锋

[5]trench[trentF]n.深沟,壕沟,战壕

[6]tusk[tQsk]n.象牙

[7]trunkn.象鼻

[8]domesticate[d[5mestikkeiit]vt.驯

养,使安于土地,教化

[9]Zaire[z[5i:r[]n.扎伊尔

[10]pittrapn.坑陷

[11]buffalo[5bQf[l[u]n.(印 度、非 洲 等

的)水牛

[12]Coorg[5ku[g]n.库格(印度一旧省)

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[13]Mysore[5maisR[]n.迈索尔(印度南

部一城市)[14]Coruba[5kR:r[b[]n.高鲁巴人

[15]campelephantn.象 园 里 训 练 有 素 的

[16]trample[5trAmpl]v.践踏,踩坏,轻

犈狊狊犪狔25 犔犻狏犻狀犵犜狅犵犲狋犺犲狉

1.Animalsocialsystemsrangefromthetemporarycoupling[1]ofearthwormstothecomplexstructuresofantsocieties,inwhichgroupinterestssoovershadow[2]individualitythattherelationshipofindividualtogroupislikethatbetweencellandorganism.

2.Amongvertebrates,somearemonogamous[3],otherspolygamous[4].Someparentscarefortheiryoung,othersleavethemtofendforthemselves.Someanimalsliveinwanderingherdsorflocksorschools,othersaresolitary[5].Someareterritorial[6],othersnomadic[7].

3.Incertainspecies,thesocialstructurechangeswiththeseason:manybirds,forexample,flocktogether[8]inthefallandwinterbutmaintainindividualterritoriesinthespringandsummer.Somespeciesadjusttheirsocialstructuredependingondifferencesinavailabilityoffoodorshelterandthebehaviorofpreyandpredators[9].Forexample,

anubisbaboons[10],ontheplain,marchinstricthierarchical[11]formation;intheforest,ontheotherhand,theymoveasadisorganizedrabble[12].

4.Animalsocialsystems,itisevident,adapttotheenvironment,asProfessorFrankMckinneyoftheUniversityofMinnesotahasfoundamongducksofthegenusAnas[13].Someducksbreedinpondsrichinfood,soasmallareasuppliesallthefamily’sneeds;

theirsocialsystemaccordinglyconsistsofsmall,exclusivelyheld,vigorouslydefendedterritoriesandmonogamouspairs.Pintails[14],ontheotherhand,livewherefoodiswidelyscattered;territoriallythereforebeinginappropriate,malesoftenstrayandmateatrandomwithanyfemale.

5.Knowledgeofhowananimallivesinnaturecanoftenhelpusunderstanditscommunicationbehavior.Forexample,whethertheanimalusesmainlyvisualorauditorysignalsdependsonhoweasyitistoseeorhearinitshabitat.Furthermore,communicationoperatesonlywithinasocialstructureandthelatterdependsonthenatureofthesignals,

whattheyareusedtoconveyandhowtheyarerespondedto.Forexample,onlyinsocialsystemsthatinvolvepermanentrelationshipsbetweenindividuals(suchasthoseofmatesorofparentsandtheiryoung)istheidentitypartoftheinformationconveyedbysignals.

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 Notes

[1]coupling[5kQpliN]n.交配

[2]overshadow[7[uv[5FAd[u]vt.遮蔽,使显得不重要

[3]monogamous[mR5nRg[m[s]adj.单

配偶的

[4]polygamous[pR5lig[m[s]adj.多配偶

[5]solitary[5sRlit[ri]adj.独处的

[6]territorial[7teri5tR:ri[l]adj.有 领

土的

[7]nomadic[n[u5mAtik]adj.游牧的

[8]flocktogether聚集在一起

[9]preyandpredator捕食者与猎物

[10]anubisbaboo[[5nju:bis5bB:bu:]n.狒

[11]hierarchical[7hai[5rB:kik[l]adj.分

等级的

[12]rabble[5rAbl]n.乌 合 之 众,下 层 社

会,拨火棍

[13]Anasn.鸭属

[14]Pintail[5pinteil]n.针尾鸭

犈狊狊犪狔26 犆狉犪狕狔犗狑狀犲狉狊犕犪犽犲犳狅狉犆狉犪狕狔犘犲狋狊

1.Thereseemstobeawidespreadbeliefthatifacompanionanimal[1]isbehavinginacrazymanner,thenitisbecausetheownersarecrazyandhavemadehimthatway.Asyoumightexpectthisbeliefismostlyheldbypeoplethatdon’thaveproblemanimals.Thisbeliefiswrongonatleasttwocounts.First,itisnotappropriatetousewordslikecrazy,psychotic[2]orneurotic[3]todescribethebehaviorofcompanionanimals.“Crazy”

doesnothaveascientificmeaningandisnotusedinhumanpsychology[4]ormedicine.Thewordspsychoticandneurotichaveveryspecificscientificmeaningsinhumanpsychology,butaren’tappropriatefordescribingproblemsinanimalsbecausetheyaredefinedintermsofhumancommunication.Therearesomesimilaritiesbetweensomehumanbehaviorproblemsandtheproblemsweseeinourpets,butwemustbecarefulnottoassumethatthecausesarethesame.Thesecondreasonthatthisbeliefiswrongisthatmostbehaviorproblemsofcompanionanimalsarenotcausedbytheirowners.Mostbehaviorproblemsthatpeoplecomplainabout,suchasdogsbarking,catsnotusingthelitterbox[5]orevenanimalsbitingpeople,arenormalbehaviorfortheanimal,

buttheyoccursattimesorinplacesthatarenotacceptabletopeople.Theseanimalsarenotcrazy,it’sjustthattheirnormalanimalbehaviorconflictswithourhumanneeds.Admittedly[6],therearesomebehaviorproblemsthatanimalsshowthataretrulyabnormal,butagainwehavelittleevidencethattheownershavecreatedtheabnormalbehavior.Mostoftheanimalsthatweseeinourbehaviorpracticeliveingoodhomeswithcaringandlovingowners.Mostareobediencetrained,getregularveterinary[7]careand

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arewellcaredfor.Despitethis,theanimalsdeveloptheirbehaviorproblemsanyway.Wedon’tknowwhysomeanimalsdevelopbehaviorproblemsandothersdon’t.Geneticpredispositions[8],earlyexperiencesorotherfactorsallmayplayarole.

2.Sometimesownersmayunknowinglycreatebehaviorproblemsoutofignorance.Apuppy[9]leftinthehouseforeighttotenhoursatatimewillsurelyhousesoil[10],andalongtermeliminationproblem maybecreated.Sometimespeopleunwittingly[11]encouragebehaviorproblems.Encouragingadogtobarkatorchaseadeliveryperson(“WhoisitRover?Gogethim!”)cancreateormakeworseabarkingoranaggressionproblem.Ownersthatcreateormakeworsebehaviorproblemsaretheexception,nottherule.

 Notes

[1]companionanimaln.同伴动物

[2]psychotic[sai5kRtik]adj.精 神 病 的

n.精神病患者

[3]neurotic[nju[5rRtik]n.神经病患者

adj.神经质的,神经病的

[4]psychology[sai5kRl[dVi]n.心理学,心理状态

[5]litterbox[5litEbRks]n.垃圾箱

[6]admittedly [[d5mitidli]adv.诚 然,无可否认

[7]abnormal[Ab5nC:m[l]adj.反常的

[8]veterinary[5vet[rin[ri]n.兽医adj.医牲畜的,兽医的

[9]predispositionn.易患病的体质

[10]puppy[5pQpi]n.(常指未满一岁的)小狗,小动物,自负的青年

[11]housesoil[5haussRil]vi.弄脏屋

[12]unwittingly[Qn5witiNli]adv.不知情

地,无意地

犈狊狊犪狔27 犉犻狊犺犪狀犱犛狅狌狀犱

1.Fishalsocommunicatewithsound.OnespeciesinparticularcausedastirinSausalito,

Californiainthe1980s.Asuccessfulantipollutioncampaign[1]hadclarifiedthewaters

ofthebay,andmadethehouseboats[2]thatlinetheshorenewlyfashionable.Butsud

denlyresidentsbeganlosingsleepbecauseofaloudhum[3]thatappearedtocomefrom

thewater.Someblamedanewlylaidpowerline.Othersthoughtthesewage[4]workshadsecretlyresumedpumpingatnight.Butthecausewas,inasense,theclearwater.

2.Cleaningupthebayhadproducedaperfectenvironmentfortoadfish[5],aslimy[6],bi

zarre[7]lookingrelativeofsearobins[8],sculpins[9]andmidshipman[10].Itturnsout

thatthetoadfishhumsalovesongtoattractmates.Andmaleshuminchorus[11]duringthebreedingseason,sometimescontinuingforanhour.Thischorusoflovesongshadsparkedtheconcernofhouseboatowners.

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3.Toadfishalsomaketwoothersounds.Grunts[12],warningsthatapparentlytellrivalmalestobackoff[13]orpotentialpredatorstostayaway,lastonlytwotenthsofasecond.Thesocalledboatwhistlelastsnearlyasecond,mayattractfemalesaswellashummingdoes,andmightidentifyindividuals.Inthedistantlyrelatedbicolordamselfish[14],femalescandistinguishindividualmalechirps[15]andmalescantellthechirpoftheirnearestneighborfromthevocalizations[16]ofmoredistantmales.Fishsoundsfunctionmainlyinmateattraction[17],butarealsousedinschoolcoordination[18],andtheytravelwellunderwater.Scientistshaveobservedfishrespondingtoasoundsignalfromhalfamileaway.

4.Fishproducesoundsinavarietyofways,oftenwithorgansmuchlessspecializedforthetaskthanthevocalapparatusofothervertebrates.Gruntsappeartocomefrom

grindingteeth[19],thesoundamplifiedbytheairfilledswimbladder[20].Andspecialmusclesinorneartheswimbladderitselfcancauseittovibratelikeadrumhead[21].

5.Neurobiologist[22]AndrewH.Bass,ofCornellUniversity,hasstudiedsoundproductioninthemidshipman,sometimescalledthesingingfish[23].Asetofspecialdrummingmuscles[24]attachtothewallsofthemidshipman’sheartshapedswimbladder.AsBassexpected,females— whodon’tsing—havesmallerswimbladdersandsmallerdrummingmuscles.ButBassfoundasurprise.Somemalessport[25]femalesizedswimbladdersandweakdrummingmuscles.Furthermore,thesemalesresemblefemalesinbodysizeandshape.These“midshipwimps[26],”whomakeuplessthan10percentofBass’sstudypopulation—don’tsingorbuildnests,andtheirsimilaritytofemalescontinuesallthewaytotheanatomyandcellularstructureoftheirbrains.Butdon’tlettheirnonmasculinebuild[27]foolyou.Theymateandpassongenesquitesuccessfully.

6.Thesmallmidshipmanmalesemployastrategyseeninmanyfishandinotheranimalsaswell.Theyaresocalledsatelliteorsneakermales[28].Themajorityofmalesfollowtheusualroute,eatandgrowtoalarge,attractivesize,competeforspace,buildand

guardanestandgruntyourheartout.Theyreaptherewardofanestfullofeggslaidbyseveralfemales.Butsneakermalesslinkaroundtheedgesofterritories,slippingintodepositsperm(sneakspawning[29])whilenormalmalesarebusyguardingandshowingoff.Theirspermdonotfertilizemanyeggsinasinglenest,buttheycansneakspawninseveral.Inasecondslystrategy,somesmallmalesreleasetheirmilt[30]intothewatersurroundinganestandfanthespermladenwatertowardthenestwiththeirfins.

7.Fishhear—orfeel—soundintwoways.Somehavesmallbonesconnectingtheinnerear[31]totheswimbladder,creatingineffectasinglelargeear.Fishhavenoouterears[32],andthereforenoneedforthemiddleearbones[33]thatconnecttheeardrum[34]

totheinnerear.Buttheydopossessaninnerearsimilartothoseofothervertebrates.8.Butfishalsodetectvibrationsinthewaterwithauniquelaterallinesystem[35]similarinmanywaystoourinnerears.Whereorganofhearinginourinnerearsformsacoil,thatoffishliesstretchedoutalongitsside.Thelaterallinetubestretchesthelengthofa

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fish,andsometimesbranchesarounditshead.Thetubeconnectstothewaterbywayofsmallporesintheskinandscales.Mucus[36]fillsthetube,justasinourcochlea[37].Whenapressurewavestrikesthefish,itjiggles[38]themucusandbendssmallhairsthatprojectintothemucusinbunches[39].Thehairstriggernerveimpulses[40],whichtraveltothebrain.Whilefishcannotdeterminethelocationofasounddetectedthroughthesingleswimbladder,theycanlocatesoundsdetectedbywayofthelateralline.

 Notes

[1]antipollutioncampaign[5Antip[5lju:

F[nkAm5pein]n.抗污染运动

[2]houseboat[5haJsbaJt]n.形如房子的

船,游艇

[3]hum [hQm]v.嗡 嗡 叫,哼n.嗡 嗡

声,嘈杂声

[4]sewage[5sju:idV]n.下水道,污水

[5]toadfish[5t[JdfiF]n.蟾鱼,豹蟾鱼

[6]slimy[5slaimi]adj.黏 糊 糊 的,(分

泌)黏液的,泥泞的

[7]bizarre[bi5zB:]adj.奇异的(指态度、

容貌、款式等)[8]robin[5rRbin]n.知更鸟

[9]sculpin[5skQlpin]n.大 头 鱼,杜 父

鱼(一种杜父鱼科的海生或淡水 鱼,具

有巨大的扁平头和突出的脊柱),饭桶

[10]midshipman[5midFipm[n]n.海军学

校 学 生,英 国 海 军 少 尉 之 候 补 军 官;

蟾鱼(一种 蟾 鱼 属 的 蟾 鱼,在 其 身 侧 有

几排发光器官)[11]chorus[5kC:r[s]n.合 唱,合 唱 队,

齐声

[12]grunt[grQnt]vi.(猪 等)作 呼 噜 声,(表示烦恼、反对、疲劳、轻蔑等)发哼声

vt.咕哝着说出n.呼噜声,咕哝

[13]backoffv.后退

[14] bicolor damselfish [5bai7kQl [

5dAmzel7fiF]n.双色小热带鱼

[15]chirp[tF[:p]n.喳 喳 声,唧 唧 声v.吱喳而鸣,尖声地说

[16]vocalization[9v[Jk[lai5zeiF[n]n.发

声法

[17]mateattractionn.伴侣吸引

[18]schoolcoordination [sku:lk[u7C:

di5neiF[n]n.群体协调

[19]grindingteethn.磨牙

[20]swimbladder[5blAd[]n.浮囊,鱼鳔

[21]drumhead[5drQmhed]n.耳鼓

[22]neurobiologist [9nju:[r[u5baiRl[dVist]n.神经生物学家

[23]singingfishn.唱歌鱼

[24]drummingmusclen.振动肌

[25]sportvt.炫耀,夸示

[26]midshipwimpn.懦弱蟾鱼 (此处是作

者造 的 一 个 词,与 midshipman相 关,

wimp意为“懦弱的”)[27]nonmasculinebuild[nJn5mB:skjulin

bild]n.非阳性身体

[28]satelliteorsneakermalen.卫星雄性,

偷偷摸摸的雄性

[29]sneakspawn[spR:n]n.偷偷产卵

[30]milt[milt]n.(充满精液的)雄鱼生殖

腺,(雄鱼的)精液,鱼白

[31]innerearn.内耳

[32]outerearn.外耳

[33]middleearbonen.中耳骨

[34]eardrum[5i[drQm]n.耳膜

[35]lateral[5lAt[r[l]linesystemn.侧线

系统

[36]mucus[5mju:k[s]n.黏液

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[37]cochlea[5kRkli[]n.耳蜗

[38]jiggle[5dVigl]v.(使)轻 摇,(使)微

动n.轻摇,微动

[39]bunch[bQntF]n.串,束v.捆成一束

[40]nerveimpulse[5impQls]n.神经脉冲

犈狊狊犪狔28 犃狀犻犿犪犾狊’犝狊犲狊狅犳犆狉狔犻狀犵犪狀犱犅犲犵犵犻狀犵

1.Throughouttheanimalkingdom,helplessoffspring[1]havewaysofdemandingattentionthatparentscan’tignore.Butalltheyelling[2]andscreaming[3]andpeeping[4]andbleating[5]maycommunicatemuchmorethanmerehungerandthirst.

2.Fromahatchling[6]magpie[7]’sfirsttentative[8]squawk[9]toanewbornbaby’scry,thecaresoliciting[10]signalsofdependentoffspringarethefirstformofcommunicationinmanyspecies.Theyarealsoamongthemostostentatious[11]formsofcommunicationaround.Writhing[12]broods[13]ofsongbirds[14],necksoutstretchedandbeaksagape[15],

confrontparentsatthenest.Chinstrappenguin[16]siblingschasetheirparentsthroughcrowdedrookeries[17]forameal.Robinchicks,jockeying[18]forpreferredfeedinglocationsinthenest,getintoshoving[19]matches.Evenbeforehatching,whenheatandnotfoodistheresourcechickscrave[20],embryonicwhitepelicans[21]vocalize[22]intheegg.Nor[23]arethesedisplayslimitedtobirdsandmammals.TadpolesofthepoisonousfrogDendrobatespumilio[24]performvigorousswimdisplayswhentheirmotherscheckonthem,andmotherfrogsoftenrespondbyleavingbehindunfertilizedeggsasfood.Eveninsectlarvaetrytogetadultattention.Immatureburyingbeetles[25]gesticulate[26]attheirparentstoearnahelpingofregurgitated[27],rottenmeat.

3.Indeed,mostoffspringdisplaysseemmuchmoreextravagantthanonewouldthinknecessarytoelicitattentionfromparentsalreadyeagertoprotectandfeedtheirown.Surelynaturalselectiondesignedmaternalbrainstoberesponsive.Theexcitedsquealsofhungrypiglets[28]andthebleatsofinsistentlambsseembetterdesignedforpestering[29]

reluctantmothersthanforconveyingasimplemessageofneed.Whyhasn’tevolutionprogrammedhumanbabiestoseekparentalfavorwithpleasantsoundsandgestures—anudge[30],forexample,orahushed[31]whimper[32]?

 Notes

[1]offspring[5RfspriN]n.(单 复 数 同

形)儿女,子孙,后代,产物

[2]yell[yel]vi.大叫,忍不住笑,呼喊

[3]screaming[5skri:miN]adj.尖叫的,令人惊愕的,引人捧腹大笑的

[4]peep[pi:p]vi.窥视,偷看

[5]bleat[bli:t]vi.羊叫声,咩咩,咩咩叫

[6]hatchling[5hAtFliN]n.人 工 孵 化 的

鱼苗或小鸟

[7]magpie[5mAgpai]n.鹊

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[8]tentative[5tent[tiv]adj.试验性的,试探的,尝试的,暂定的

[9]squawk[skwR:k]v.发 出 叫 声,诉

苦,抗议n.粗粝的叫声

[10]solicit[s[5lisit]v.恳求

[11]ostentatious[7Rsten5teiF[s]adj.卖

弄的,装饰表面的

[12]writhe[raiT]v.翻腾,局促不安

[13]brood[bru:d]n.(动 物 中 鸟 或 家 禽

的)一窝,(同种或同类的)一伙

[14]songbirdn.鸣禽,鸣鸟,女歌手

[15]agape[E5geip]adv.张口发呆地,目

瞪口呆地

[16] chinstrap penguin [5tFinstrAp5peNgwin]n.帽带企鹅

[17]rookery[5rukk[ri]n.群 居 地,穴,白

嘴鸦的群居地,海豹等之穴,破旧而拥

挤的住房群,贫民窟

[18]jockey[5dVRki]v.谋求n.职业赛马

骑师,(机器的)操作员

[19]shove[FQv]vt.[口]推挤,猛推,强

使vi.推

[20]crave[kreiv]v.恳求,渴望

[21]pelican[5pelik[n]n.鹈鹕

[22]vocalize[5v[uk[laiz]v.发声

[23]nor[nC:]conj.也不

[24]Dendrobatespumilion.草莓箭毒蛙

[25]buryingbeetle[5beriiN5bi:tl]n.埋

葬虫

[26]gesticulate[dVes5tikjUleit]v.做 姿

势表达,用手势谈话

[27]regurgitate[ri5g[:dViteit]v.(使)涌

回,(使)流回,(使)反刍

[28]piglet[5piglit]n.小猪

[29]pester[5pest[]vt.使烦恼,纠缠

[30]nudge[nQdV]n.用肘轻推,轻推为引

起注意

[31]hush[hQF]v.使安静或沉默n.安静

[32]whimper[5wimp[]vi.呜咽,哀诉,呜

咽的说

犈狊狊犪狔29 犉狉狅犵犆犪犾犾狊

1.Asduskfallsoveraswampy[1]pond,thechorusbegins.Firstonefrogcroaks[2],alittle

hesitantly.Soonanotherjoinsin.Suddenlythepondresonates[3]withthevoicesofdozensofmalefrogs,eachsignalinghisspecies,availabilityandqualificationsasafather.Twopopulationsofthesamespecies,separatedgeographically—ahighwayrunningthroughaswamp,forexample—developdialects,slightdifferencesintheircalls.Inmostspecies,onlymalescall,thoughthefemalemidwifetoad[4]outshouts[5]hermate.Asuddenforeignsoundsilencesthemoneandall.Butsoonasinglevoicestartsagain,

followedbyanotherandanother.2.Thesoundofapondfulloffrogscanreachdeafeninglevels,faroutofproportiontothetinybodiesproducingthesound.Anairsac[6]onthefloorofthefrog’smouthenablesit

todotworemarkablethings.First,whenit’sexpanded,thesacactsasaresonator[7],

likethehollowbodyofaviolin.Second,byforcingairintothesacfromthelungs,thenbackintothelungs,afrogcancroakcontinuously,evenunderwater.Theloudestfrogsbreedintemporaryponds.Whenthewater’savailable,themalesmuster[8] mates

quickly,forallfrogslayeggsonlyinwater,andthetadpolesmustgrowlegsbeforethe

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temporarypondsdryup.3.Butforsheercacophony[9],theyearroundsingingoftropicalfrogsbeatsall.Inthetropicalrainforest,oneoftherichestecosystemsonearth,aswamphousesmanyfrogspecies.Maleswouldgainnothingbyattractingandattemptingtomatewithfemalesofanotherspecies,sotheyhavetomaketheirsignalscutthroughthedin[10].

4.ThemaleLeptodactylusocellatus[11],whichlivesinSouthAmerica,callsatabout250to500Hz(roughlyanoctave[12],frommiddleC[13]toabovemiddleC[14]).Hisvolumeisnomatch,however,foraneighboringspecies,whichoverlapshisfrequencyrangeandcancroak40decibelslouder.That’slikethedifferencebetweenaconversationaltoneandthenoiseonafactoryfloor.L.ocellatus,however,hasevolvedawaytocircumvent[15]thispotentialproblem —bycroakingunderwater.

5.Becausesoundtravelswellunderwater,butdoesn’tcrosstheinterfaceintotheair,L.ocellatusavoidssoniccompetitionwithoutchanginghispreferredoctave.Inarichenvironment,speciesdividetheenvironmentupintotinierandtinierslices,eachbecomingaspecialist.Singingunderwaterrepresentsanextrememethodofdividingthe“airwaves[16]”.Mostfrogscroakdistinctivelybyvaryingthepitch[17]oftheircalls,orbyvar

yingthepatternofcroaksinasong.Evenwhentheycandistinguishthecallofmalesoftheirownspecies,though,femalefrogsmustdeterminethedirectionfrom whichitcomes.Thispresentsaproblem.

6.Humansandothermammalscandeterminethedirectionofasoundbecausetheirbrainsdetectdifferencesinloudnessandtimeofarrivalateachoftheirtwoears.Forthissystemtowork,thewavelengthofthesoundmustbemuchsmallerthanthedistancebetweenthetwoears.Thelongerthewavelength,theharderitistotellwherethesoundcamefrom.Thecrest[18]ofalongsoundwavemayhitthenearearonlyatinyfractionofasecondbeforeithitsthefarear.Acomparativelylongtimelater,thenextcrestreachestheears.Thisiswhysomestereosystemscontainonlyasinglelowfrequencywoofer[19],whichthelistenercanplaceanywhereintheroom.Bycontrast,thehighfrequencytweeters[20]andmidrangespeakers[21]mustbeseparatedandproperlyplacedtogivethestereoillusion[22]ofanorchestra[23]intheroom.

7.Humanshearonlyupto20000Hz,andthehighestnoteonthepianoisonlyalittleabove4000Hz.Butmanymammalshearextremelyhighfrequencies,upto60000Hz,

quitewell.Thesesoundwavesaremuchshorterthaneventhetiniestmammalheads.Frogs’highfrequencyhearingisnotassharp.Theytopoutat10,000Hz,makingthedistancebetweentheireardrumstooshorttolocalizethehighestpitchestheyhear.Sohowdofemalesfindtheirmate?Scientistsstudyingthecoquifrog[24]ofPuertoRico[25],

Eleutherodactyluscoqui[26],thinktheyhavealead.8.Onewayfrogscanlocalizesoundisbyhearingasoundtwiceinthesameear.Becauseofthefrog’sheadanatomy,soundcantravelfromthemiddleeardowntheEustachiantube[27],acrossthefrog’smouthcavity[28],uptheotherear’sEustachiantubeandintothemiddleear.Soundcanthenaffectthenearearofafrog,forexample,twice.First

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whenthesoundstrikestheeardrum,andsecondwhenitarrivesabitlaterbywayofthemouthandEustachiantubesfromthefarear.Thesetwosoundsmayarriveoutofphase[29],withpeaksandtroughs[30]interactinginawaythatgivesthefrog’sbrainaclueastowherethesoundcamefrom.Thispathwaydoesn’taffectmammalsbecauseourmouthandearanatomydifferfromthatoffrogs.

9.Bymappingvibrationinthefrog’sbodywithlasers,thescientistshavefoundthataparticularspotoverthelungsofsomespeciesvibratesaswellastheeardrum.Theyproposethatthebodywallhereactslikealargeeardrum,providingyetanotherpathwayforsoundtotraveltotheeardrum —fromlungtomouthtoEustachiantubetomiddleear.Thismayfurtherincreasetheprecisionwithwhichfemalefrogsfindtheirprinces.

 Notes

[1]swampy[5swRmpi]adj.沼 地 的,多

沼泽的,潮湿的

[2]croak[kr[uk]n.蛙或鸦的叫声

[3]resonate[5rez[neit]v.(使)共 鸣,(使)共振

[4]midwifetoadn.产 婆 蟾(雄 蟾 以 后 脚

带着卵的方式保护卵,故名)[5]outshout[7aUt5FaUt]vt.叫 得 比

……响

[6]airsac[sAk]n.气囊

[7]resonator[5rez[neit[]n.共振器,共

鸣器

[8]muster[5mQst[]v.集 合,召 集,征

召,鼓起(勇气等),集聚

[9]cacophony[kA5kCf[ni]n.刺 耳 的 音

调,不谐和音,杂音

[10]dinn.喧嚣

[11]Leptodactylusocellatusn.眼 斑 细 趾

[12]octave[5Ckteiv]n.八个一组的物品,八度音阶

[13]middleCn.(音)中央C,中央C音

[14]abovemiddleC高中央C音,超高音

[15]circumvent[7s[:k[m5vent]vt.围绕,包围,智取

[16]airwaven.电视,广播的频道

[17]pitch[pitF]n.音调

[18]crest[krest]n.波峰

[19]woofer[5wUf[]n.低音用扩音器

[20]tweeter[5twi:t[]n.高音喇叭

[21]midrangespeakern.中音喇叭

[22]stereoillusion[5sti[ri[Ui5lU:V[n]

n.立体感觉

[23]orchestra[5C:kistr[]n.管 弦 乐 队,乐队演奏处

[24]coqui[5k[Ukwi]frogn.科奎蛙

[25]PuertoRico[5pw[:tou5ri:k[n]n.波多黎各(拉丁美洲)

[26]Eleutherodactyluscoqui多米尼加树蛙

[27]Eustachian[ju:s5teiFi[n]tuben.耳

咽管

[28]mouthcavityn.口腔

[29]outofphaseadv.异相地,不协调地

[30]trough[5trC:f]n.波谷

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犈狊狊犪狔30 犇狅犾狆犺犻狀狊

1.Amongnonhumananimals,birdstakefirstplaceinimitating[1]sounds,includinghumanwords.Butperhapssurprisingly,marinemammalsplacearespectablesecond[2].Certainharborseals[3]havelearnedtobarkout(barely)recognizablewords,andwhalesimitateeachotherduringthedevelopmentoflong,complexsongs.Butthemostwidelystudiedmarinemammalvocalizersaredolphins[4].

2.Dolphinscommunicatewithagreatnumberofdifferentsounds,fromtherepetitiveclicks[5]usedforecholocation[6](andpossiblytocommunicate)towhistlesandgrunts;

incaptivity,theycanimitatehumanwordstosomeextent.Theirecholocationappearstrulyremarkable.Ablindfoldeddolphincanfindanobjectthesizeofapennyonthebottomofaswimmingpoolandcandistinguishsmallobjectsbasedontheirshapeandthematerialthey’remadeof.Butmoreremarkable,perhaps,arethevocalizationsmoreobviouslyusedforcommunication.

3.Whistlesatfirstappeartosayonesimplething:“Hi!I’mFlipper.”Researchsincethe1960shasindicatedthatdolphinseachhaveauniquewhistle,calledasignaturewhistle[7].Thisimpliesdolphinscanproduceseveraldifferentwhistles—atleast10to25,

thenumberofindividualsinanaveragesizedgroup.Furthermore,theymustlearnthesignaturewhistlesofeveryotherdolphininthegroup.Reviewsofthewhistlesofmorethan100dolphinssuggesttheydonotchooseasignaturefromafixedsetofwhistles,

butdevelopanindividualwhistle.Asthedolphinmatures,itssignaturebecomessomewhatstereotyped[8].Toidentifyindividualsbytheirwhistles,dolphinsmustalsohavethementalabilitytolinktheindividualwhistlewithanindividualdolphin.Thisseemslikely,judgingfromexperimentsteachingdolphinstolinkhumanhandsignals,humanwhistlesandevenelectronicallygeneratedsoundstoparticularobjects(forexample,

imitatingthetuneto“MaryHadaLittleLamb”whenshownaFrisbee[9]).4.Behaviorists[10]PeterTyackofStanfordUniversityandLaelaSayighoftheUniversityofNorthCarolinaatWilmingtonstudiedapopulationofwilddolphinsnearSarasota,Florida.Thesedolphins,agroupstudiedfordecadesbyRandalWellsoftheChicagoZoologicalSociety,remaininonearea,soresearcherscanrepeatedlyfindindividuals,

whichtheyrecognizebythedolphins’individualmarkings.Becausetheycan’ttellwhichdolphinismakingaparticularsoundinagroup,theyrecordthedolphinsindividuallyaftercorralling[11]themwithanet.Thetechniqueprovidesonlyaseminatural[12]

environment,buthasyieldedintriguinginformation.5.First,Sayighconfirmedthatindividualdolphinshaverecognizablesignaturewhistles,

andthatthosewhistlesremainstableforatleastadecade.Shealsofoundthatmothersandcalves[13]remaininvocalcontactwhenoneisinthecorralandtheotherswimmingnearby.WhenSayighbeganrecordingnewborncalfwhistles,shefoundafaint,quaver

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y[14]soundthatvariedfromwhistletowhistle,likethewrittensignatureofayoungchild.Bytheageofone,thecalfhadfirmedupanindividualwhistlethatthenremainedmoreorlessconstantforadecade.

6.Sayighalsofoundmaleandfemalecalvesdevelopwhistlesdifferently.Afemalecalflearnsawhistledistinctlydifferentfromhermother’s.Abrother’swhistle,ontheotherhand,developsfromavariablebabywhistletoanadultformcloselyresemblinghismother’s.Inthispopulationofdolphins,atleast,femaleswithnewborncalveshangoutwiththeirmothers,grandmothersandotherfemales,formingalonglastinggroup.Similarsignaturewhistlesamongayoungfemale,hermother,grandmotherandevenotherfemalescouldleadtoconfusion,likehavingafamilywithtwomemberswiththesamename;thewrongpersonisalwaystakingthetelephonecall.Malecalvesleavethegroupwhentheymature,sotheystandlittlechanceofbeingmisidentified[15].

7.Whilethismodificationofsignaturecallsappearstorelyonlearning,Sayighhasnotruledoutageneticbasis.Forexample,ifthesignaturecallweregenetic,itmightresideonintheXchromosome.AfemalewouldinherittwoXchromosomes,onefromherfatherandonefromhermother.Hersignaturewouldthendifferfromeither.Amale,ontheotherhand,inheritsonlyoneX,fromhismother,andhiscallwouldresemblehers.

8.Studyingsignaturewhistlescanposeproblemsforresearchers.Althoughhumanscanheardolphinwhistlesunderwater,theycannotlocatethesourceofthewhistles.Norcantheylocatethesourceofthewhistlespickedupbyunderwatermicrophonesandbroadcasttopside.Isolatingthedolphinssolvestheproblemofidentifyingwhoissqueaking[16].Butevenwhentwodolphinscancommunicatebywayofasortofunderwaterwalkietalkie[17]—astheycouldinoneexperiment—isolationseverelydisruptssocialcommunication.

9.PeterTyackinventedonesolutiontotheproblem,allowinghimtoreliablyrecordthewhistlesoftwoormoreindividualdolphins.Hecallshisinventionthevocalight[18].ThethreeandahalfinchlongdevicelookslikeacrossbetweenasmallflashlightandamodelofStarTrek’sU.S.S.Enterprise[19].Asuctioncupholdsthedevicetotheslickdolphinskininfrontoftheblowhole.Arowoflightemittingdiodes[20]pointstothefrontandabatterycasetotheback.Inside,amicrophonepicksupthedolphin’ssoundsandelectronicsilluminatethediodesinresponsetothesounds.Thelouderthesounds,themorediodeslightup.

10.Tyackfirststudiedtwodolphins,ScottyandSpray,wholivedinanaquarium[21]calledSealandinBrewster,Massachusetts.Tyacksetupthetwowithvocalights,onewithreddiodesandonewithgreen.Heandotherobserverscalledoutthecolorandnumberofdiodeswhenevertheyheardawhistlepickedupbyanunderwatermicrophone.Ataperecordercapturedboththewhistlesandtheobservers’voices.

11.Bydisplayingthewhistlesassonograms[22],Tyackfoundmorethanthreequartersfellintotwoeasytorecognizecategories.TheType1whistlerises,swoopsdowntoalow

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erpitchedhalfsecondlongwhistle,andthenrisesslightly.TheType2whistlealsorises,fallsandlevelsout,butthenrisesabruptlyattheend.Althoughbothdolphins

producedbothkindsofwhistles,Tyacknoticedindividualvariations.Spray’sType1wasnotidenticaltoScotty’sType1,andtheirType2whistlesdifferedevenmore.Interestingly,thetwodolphinssplittheirwhistlesbetweenthetwotypesdifferently.TwothirdsofSpray’swhistlesfellintotheType1category,whilealmostthreequartersofScotty’swereType2.TyackinterpretstheseresultstomeanthatType1wasSpray’ssignatureandType2Scotty’s.Eachdolphinimitatedtheother’ssignaturewhistlesomeofthetime,Tyackcontends,perhapsusingtheotherdolphin’ssignaturewhistleasalabelorname.

12.Thedolphinsalsowhistledvariationsonthosetwothemes—theyleftpartsout,variedthedurationofthewhistle,changedthepitchslightlyandvariedtheshapeofthesoundsasseenonasonogram.Tyackmaintainsthedolphinscoulddetectthesevariationsandthemanywhistlesthatfellintoneithercategory.

13.Sprayunfortunatelydied,leavingScottyinisolation.Tyackreturnedaftertwoyears,

curioustoseeifScotty’svocalizationshadchanged.ScottynolongerusedSpray’sfavoritewhistleatall.Andhiswhistlesingeneralhadbecomequieterandbriefer,lendingweighttotheideathatdolphinwhistlesfunctionassocialcommunication.

14.Giventhisevidentcomplexity,dolphins’vocabulariesmaywellencompassmuchmorethan“Hi!I’mScotty.”and“Hi!I’mSpray.”

15.Althoughdolphinvocalizationsinthewildmaystretchbeyondmeresignaturewhistles,

pastattemptstoreadimitationofhumansoundsintotheirsqueakyvoicesstandonshak

yground.Eventoday,rapidevaluationoftheirhighpitchedsoundsprovesdifficult.Furthermore,theirsleek,fingerlessflippers[23]makeitdifficultforthemtoproducethekindsofartificialcommunication— handgesturesandkeyboarduse—thatapescanmuster.Butresearchhasmovedaheadontheothersideofcommunication,dolphins’abilitytounderstandlanguage.

16.LouisM.HermanandhiscolleaguesattheKewaloBasinMarineMammalLaboratory,

UniversityofHawaiiatManoa,havetaughtfourwildcaughtdolphinsartificiallangua

ges.Onelanguageconsistsofcomputergenerated,highpitched“words.”Inthesecond,atrainerconveyswordswithhandandarmgestures.Neitherlanguagebearsanyresemblancetohumanlanguageexceptinthatbothcontaingrammaticalrules.Eachlan

guagecomprisesabout40words,nounssuchas“channel,gate,person”and“ball;”

verbssuchas“under”(thegoimplied)and“fetch;”andmodifierssuchas“surface,

bottom,right”and“left.”

17.Usingtheselanguages,Hermancanaskanumberofquestionsaboutdolphins’abilitytocomprehendwordsasreferentstospecificobjectsandtounderstandthattheorderofthewordsmakesadifference.Unlikehumangradeschoolers,thedolphinsneverreceivedanygrammarlessons.Insteadtheylearnedtherulesbyexample.“PhoenixAkeunder,”forexample,meansthetrainerwantsPhoenixtoswimunderAkeakamai(Ake

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forshort).ThegesturallanguagelearnedbyAkeincludedareversegrammar,topreventwordbywordresponses.Thedolphinreceivingagesturalcommandmustunderstandthefulltwoorthreewordsentencebeforebeginningtorespond.

18.Hermanfoundthatthedolphinslearnedbothwhateachwordreferredtoandhowtointerprettheorderofthewords.Forexample,Akedistinguishedbetweengesturalsentencessuchas“righthoopleftFrisbeefetch”and“lefthooprightFrisbeefetch.”Thefirstsentencemeans“TaketheFrisbeeonyourlefttothehooponyourright.”Successwithsuchsentencesdemonstratesthedolphins’abilitytounderstandboththeseman

tic[24](wordmeaning)andsyntactic[25](sentencepattern)componentsofthelanguage,

Hermanwrites.19.Ake,however,hasgonebeyondmerelyrespondingastrained.Sheeveninventsher

ownlogicalresponsestounusualsituations.Ifatrainercommands“Frisbeehoopin,”atwogesturesequenceaskingAketoputthehoopontopoftheFrisbee,Akenormallycomplies.ButAkehasalsolearnedtouseyesandnopaddles.ForexampleifeithertheFrisbeeorthehoopwereunavailable,thetrainerswouldexpecthertopressthenopaddle.Sometimes,askedtheabovequestionwithbothobjectsinthetank,Akewouldputthehoop—theobjectthecommandaskshertomanipulate—ontheyespaddle,abehaviorsheinvented.IftheFrisbeeisnotinthetank,Akewillputthehoopontheno

paddle.If,ontheotherhand,thehoopismissing,shewillnotmovetheFrisbee—thetrainerdidn’taskherto—butwillpressthenopaddle,meaningshecan’tcomplywiththecommand.

20.Akerespondstonovelcombinationsofwordscorrectly,showingunderstandingofboththewordsandthesequence.Butwhatdoesshedowithaconstructionthatmakesnosense?Akewillmoveanobjecttomakeitpossibletocomplywithacommand.Shewillliftahoopthat’slyingonthebottomofthetanksoshecanswimthroughit,forexam

ple.Ifinsteadsheseesasentencethatgivesanimpossiblecommand,suchas“personwaterfetch,”Akedoesnothing.Shecan’tmovethewatertotheperson.Amorecom

plexkindof“impossible”command,“personwaterhoopfetch,”containstoomanynouns.InthisinstanceAkesensiblyignoresthenounwaterandinterpretsthesentenceas“takethehooptotheperson.”Shehasinterpretedtheimpossible“water”asamistake,muchlikeahumanwillassumeaduplicatedwordrepresentsatypographical[26]error.Hermanseestheseuntaughtresponsesasindicationsthatdolphinsmakeamentalrepresentationofthegrammaticalrulesoftheirartificiallanguage.Byreferringtothismemoryofthestructure,theycanmakesenseofnovelorevennonsensicalsentences.

21.Apictureisworthathousandwords,thesayinggoes.Inthisdigitalage,isapicturecomposedononlyeveryotherpixel[27]worthonlyfivehundred?Onthecontrary,wecanstill“read”apicturewithalargepartofthedigitaldetailmissing,animageofAbrahamLincolnmadeofonlyafewdozenblocksofcolor,forexample.HermanwonderedwhetherPhoenixandAkecould“read”gesturalcommunicationwithreduceddetail.FirsthepresentedavideotapeofatrainertothedolphinsonanunderwaterTV

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monitor.Theyrespondedalmostaswellastotherealtrainer.Nextheblankedouttheheadandtorso[28],leavingonlythearms,thenremovedthearms,andfinallypresentedonlytwomovingwhitespotstorepresentthehands.Thedolphinsrespondedtoallofthesepresentations,theircorrectresponsesfallingoffonlywiththelast,mostabstractpresentation.Eventhisminimalist[29]communicationelicitedmorecorrectresponsesthanchancewouldpredict.Humantrainers(collegestudents)withfourmonthsofexperienceinthegesturallanguagedidaboutaswell.

22.Fromtheseandotherstudies,Hermanconcludesthatdolphinsusewordsoftheartificiallanguagetorefertoobjectsinanabstractway,andcanmakesenseoftheartificialgrammaraswell.

 Notes

[1]imitate[5imiteit]vt.模仿,仿效,仿

制,仿造v.模仿

[2]marinemammalsplacearespectablesecond.海洋 哺 乳 动 物 处 于 可 敬 的 第

二位

[3]harborseal[5hB:b[si:l]n.斑海豹

[4]dolphin[5dClfin]n.海豚

[5]click[klik]v.发出滴答声n.滴 答 声

发出滴答声

[6]echolocation[ek[Jl[J5keiF[n]n.回

声定位能力,回声定位法

[7]signaturewhistle[5signitF[hwisl]n.签名哨

[8]stereotyped[5steri[Jtaipt]adj.套用

老调的

[9]frisbee[5frizbi:]n.飞盘(塑料投掷玩

具)[10]behaviorist[bi5heiv[rist]n.行为主义

[11]corral[kR:5rB:l]n.畜栏vt.关进畜

[12]seminatural[9semi5nAtF[r[l]adj.半自然的

[13]calf[kB:f]n.小海豚

[14]quavery[5kweiv[ri]adj.震音的,颤

声的

[15]misidentify[9misai5dentifai]vt.识别

[16]squeak[skwi:k]n.尖 叫 声,吱 吱 声

v.发出尖叫声

[17]walkietalkie[5wR:ki5tC:ki]n.无线

电话机

[18]vocalight[5v[uk[5lait]n.红 外 线 声

场系统

[19]StarTrek’sU.S.S.Enterprise星 际

旅行的美国“企业”号船模。[20]diode[5dai[Ud]n.二极管

[21]aquarium [[5kwZ[ri[m]n.养 鱼 池,玻璃缸,水族馆

[22]sonogram[5sCn[7grAm]n.语图

[23]flipper[5flip[]n.鳍状肢

[24]semantic[si5mmAntik]adj.词法的,语义的

[25]syntactic[sin5tAktik]adj.句法的

[26]typographical[7taip[5^rAfik[l]adj.印刷上的,排字上的

[27]pixel[5piks[l]n.像素

[28]torso[5tC:s[u]n.未完成的(不完整

的)作品,残缺不全的东西;躯干

[29]minimalist[5minim[list]n.最低限要

求者,最低纲领主义者

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犝犖犐犜09 犉犗犗犇,犖犝犜犚犐犜犐犗犖犃犖犇犎犈犃犔犜犎

犈狊狊犪狔31 犉狅狅犱

1.Ithasbeensaidthat“wearewhatweeat”[1],andfromaphysiologicalpointofviewitisthefoodweeatthatbuildsourbodiesandinfluencesourgeneralhealthanddisposition[2].

2.Oneofthesaddestfeaturesofthemodernworldisthatmillionsofpeopleroundthe

globedonothaveenoughtoeatandmanymoredonothavetherightkindsoffoodre

quiredforgoodhealth.Weareconstantlyfacedwith,thestarkcontrast[3]betweennationsinthedevelopedcountrieswhohavemorefoodthantheyneed,andthemillionsinmanydevelopingcountrieswhoarehungryandoftenstarving.

3.Inordertobehealthy,manneedsabalanceddiet[4]containingprotein,fat,carbohydrate[5],vitaminsandminerals[6].Thecarbohydrateinbread,rice,potatoesandsugar

y[7]foodsprovideenergyforthebody.Toomuchcarbohydrate,however,resultsinobesity[8],whichcanendangerhealth.Thefatsandoilsinmilk,cream,butter,cheeseandfatmeat[9]providethebody’smainstoredfoodandcontaintwiceasmuchenergyascarbohydrates.Theproteinincheese,eggs,meat,fishandmilkpromotegrowthandrepairdamagetothebody’stissues.Thebodyalsoneedssmallamountsofvitaminsandminerals.Providedaperson’sdietconsistsofavarietyoffoodssuchasmeat,fish,

eggs,milk,greenvegetablesandfruit,therequiredamountsofvitaminsandmineralsaretakenin.

4.Foodisadailynecessity[10]forlife,butthewayinwhichitispreparedandservedisanintegralpartofeveryculture.Comparethewayinwhichmeat,fish,andvegetablesare

preparedinCantonesecooking[11]withthewaytheyarepreparedinIndian,FrenchofSpanishcooking[12]anditisimmediatelyapparenthowdifferentfoodpreparationisinthevariouscultures.

5.Historically,thedietsofdifferentsocietieshavebeendictatedbysuchfactorsasclimate,soilandtheeaseordifficultyoftransportingfoodsfromoneplacetoanother.ThesimpledietoftheBedouinArab[13],consistingofdates[14],grainandoccasionallymeatandvegetablesresultedfromanaridenvironmentwhichonlyallowedafewfoodstobeproduced.Ontheotherhand,acountry,suchasFranceendowed[15]asitiswithagoodclimateandrichsoil,hasalwayshadanabundanceandgreatvarietyoffoods.Consequently,Frenchcuisine[16]hasdevelopedintooneofthegreatcomplexityandva

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riety.6.Thekindsoffoodspeoplebecomeaccustomedtointheearlyformativeyears[17]becomeanintegralpartoftheirpsychologicalmakeup.Iftheymovetoanothercountryandculture,theytendtotaketheireatinghabitswiththemandtoclingtothestyleoffoodtowhichtheyareaccustomed.Itispsychologicallyreassuring[18]toeatthefoodsoneisusedto:thebestwaytomakeaforeignvisitorfeel‘athome’istoofferthemthekindoffoodtheywouldeatintheirowncountry.

7.Whendiscussingfoodanddiet,itisalwaysnecessarytotreattheworld’spopulationastwodistinctsections:thosewhohavefoodinrelativeabundanceandthosewhosuffershortagesofeventhemostbasicfoods.Theinhabitantsofdevelopedcountriesbenefitfromtheirwealthandtheadvancesinfoodtechnology.Refrigeration,foodpreservationandrapidtransportsystemsallowpeopleinBritain,forexample,toenjoyfoodsfromallpartsoftheworld.Unabletogrowsufficientfoodfortheirneeds,theBritishimportawidevarietyoffoods,fromthehumble[19]potatotoexotic[20]tropicalfruits.Foodprocessinghasmeantthattheseasonsnonlongerdictatediet:vegetablessuchaspeasandbeansarecannedorfrozenandareavailablethewholeyearround;softfruitssuchasstrawberries[21]whichareonlyproducedlocallyforashortseason,canbeimportedfromotherpartsoftheworld;citrusfruitsandbananas,whichdonotgrowatallintemperate[22]Britain,arebroughtinfrom Mediterranean[23]andthetropics[24]andarecontinuouslyavailable.

8.Thedevelopedcountriesdo,however,payapenaltyforhavingsuchanabundanceoffood:obesityandtheconcomitant[25]diseasessuchasheartdiseasearemoreprevalent.IthasbeensaidthattheFrench,forexample,whoconsumeaparticularlyrichdiet,

commitsuicidewithaknifeandfork.Butevenintherichcountries,aneconomicrecessioncanaltereatinghabits.Althoughsomedevelopednationshavebecomeslightpoorer,theresulthasnotbeendamagingandmayevenprovetobeagoodthinginthatthepeopleinthesecountrieswilleatalittleless.Theeffectsofeconomicrecessiononmanydevelopingcountries,however,havebeendisastrous,withfamine[26]anddeathsweepingthroughvastareasofAfrica.Althoughdroughtisaprincipalcauseofthisfamine,

theeconomicpressuretoproducecashcrops,suchascotton,forexporthasreducedtheabilityofthesecountriestoproducefoodcropsfortheirownpeople.Alreadysaddled[27]

withhugeforeigndebts,manydevelopingcountriescannotbuythefoodtheyneedfromabroad.Fortunately,thedevelopedcountrieshavereactedtothefaminecrisisandareprovidingfoodaidfromtheirembarrassinglyhighfoodsurpluses.Meanwhile,overlargepartsoftheglobe,hungrypeoplearewonderingnotwhattoeat,butiftheywilleat.

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 Notes

[1]wearewhatweeat食色,性也

[2]disposition[disp[5ziF[n]n.性情

[3]starkcontrastn.鲜明对比

[4]balanceddiet[5dai[t]n.平衡膳食

[5]carbohydrate[5kB:b[U5haidreit]n.碳水化合物

[6]mineral[5min[r[l]n.矿物质

[7]sugary[5FUg[ri]adj.含糖的,甜的

[8]obesity[[u5bisiti]n.肥胖

[9]fatmeatn.肥肉

[10]dailynecessityn.每日必需品

[11]Cantonesecooking[7kAnt[5ni:zkukiN]

n.广东烹饪

[12]Spanishcookingn.西班牙烹饪

[13]Bedouin[5bedUin]Arabn.贝多因人

(一个居无定所的阿拉伯游牧民族)[14]daten.枣子

[15]endow[in5daU]v.捐赠,赋予

[16]cuisine[kwi5zi:n]n.厨房烹调法,烹

饪,烹调风格

[17]formativeyearsn.形成时期

[18]reassuring[9ri:[5FJ[riN]adj.安 心

的,可靠的

[19]humble[5hQmbl]adj.卑下的,微贱

的,谦逊的,粗陋的

[20]exotic[ig5zCtik]adj.异 国 情 调 的,外来的,奇异的

[21]strawberry[5strR:b[ri]n.草莓

[22]temperate[5temp[rit]adj.有 节 制

的,适度的,戒酒的,温带的

[23]Mediterranean[7medit[5reinj[n]n.地中海

[24]tropics[5trRpiiks]n.热带地区

[25]concomitant[k[n5kCmit[nt]adj.随

之而来的

[26]famine[5fAmin]n.饥 荒,[古]饥 饿,严重的缺乏

[27]saddle[5sAdl]v.承受

犈狊狊犪狔32 犞犻狋犪犿犻狀狊

1.Intheearlydaysofseatravel,seamenonlongvoyageslivedexclusively[1]onmeatand

biscuits.Manyofthemdiedofscurvy[2],adiseaseofthebloodwhichcauseswollen

gums[3],livid[4]whitespotsonthefleshandgeneralexhaustion[5],Ononeoccasion,in

1535,anEnglishshiparrivedinNewfoundland[6]withitscrew[7]desperatelyill.The

men’slivesweresavedbyIroquoisIndians[8]whogavethemvegetableleavestoeat.Graduallyitcametoberealizedthatscurvywascausedbysomelackinthesailors’dietandCaptainCook,onhislongvoyagesofdiscoverytoAustraliaandNewZealand,establishedthefactthatscurvycouldbewardedoff[9]bytheprovisionoffreshfruitforthesailors.

2.Nowadaysitisunderstoodthatadietwhichcontainsnothingharmfulmayyetresultinseriousdiseaseifcertainimportantelementsaremissing.Theseelementsarecalled‘vitamins’.Quiteanumberofsuchsubstancesareknownandtheyaregivenletterstoi

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dentifythem,A,B,C,D,andsoon.Differentdiseasesareassociatedwithdeficienciesofparticularvitamins.EvenaslightlackofVitaminC,forexample,thevitaminmostplentifulinfreshfruitandvegetables,isthoughttoincreasesignificantlyoursusceptibilitytocoldsandinfluenza.

3.Thevitaminsnecessaryforhealthybodyarenormallysuppliedbyagoodmixeddiet,includingavarietyoffruitandgreenvegetables.Itisonlywhenpeopletrytoliveonaveryrestricteddiet,sayduringextendedperiodsofreligiousfasting,orwhentryingtoloseweight,thatitisnecessarytomakespecialprovisiontosupplythemissingvitamins.

4.Anotherexampleofthedangersofarestricteddietmaybeseeninthediseaseknownas“beriberi”[10]whichusedtoafflictlargenumbersofEasternpeopleswholivedmainlyonrice.Intheearlyyearsofthiscentury,aDutch[11]scientistcalledEijkmanwastryingtodiscoverthecauseofberiberi.Atfirsthethoughtthatitwastransmittedbyagerm.HewasworkinginaJapanesehospital,wherethepatientswerefedonricewhichhadhadtheouterhuskremovedfromthegrain.Itwasthoughtthiswouldbeeasierforweak,sickpeopletodigest.Eijikmanthoughthisgermtheorywasconfirmedwhenhenoticedthechickensinthehospitalyard,whichwerefedonscraps[12]fromthepatients’plates,werealsoshowingsignsofthedisease.Hethentriedtoisolatethegermhethoughtwascausingthedisease,buthisexperimentswereinterruptedbyahospitalofficial,whomdecreedthatthehusklesspolishedrice[13],eventhoughleftoverbythepatientswastoogoodforchickens.Itshouldberecookedandthechickensfedoncheap,coarserice[14]withtheoutercoveringstillonthegain.

5.Eijikmannoticedthatthechickensbegantorecoveronthenewdiet.Hebegantoconsiderthepossibilitythateatingunmilledricesomehowpreventedorcuredberiberi,

whilethatalackofsomethinginthepolishedriceorsomeingredientinthehuskmightbethecauseofthedisease.Indeedthiswasthecase.TheelementneededtopreventberiberiwasshortlyafterwardsisolatedfromricehusksandisnowknownasvitaminB1.Themilledrice,thoughmoreexpensive,wasinfactperpetuating[15]thediseasethehospitalwastryingtocure.Nowadays,thisterriblediseaseismuchlesscommonthankstoourknowledgeofvitamins.

 Notes

[1]exclusively[ik5sklU:sivli]adv.排外

地,专有地

[2]scurvy[5sk[:vi]adj.下 流 的,卑 鄙

的,无礼的n.[医]坏血病

[3]gum[gQm]n.齿龈

[4]livid[5livid]adj.铅 色 的,(被 打 得)

青紫色的

[5]exhaustion[ig5zR:stF[n]n.耗 尽 枯

竭,疲惫,筋疲力尽,竭尽,详尽无遗

的论述

[6]Newfoundland[7njU:f[nd5lAnd]n.纽芬兰(岛)(加拿大一省)

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[7]crew[kru:]n.全体船员,(工作)队[8]IroquoisIndian[5ir[kwRi5indj[n]

adj.易洛魁族印第安人

[9]ward[wR:d]offv.避开,挡住

[10]beriberi[5beri5beri]n.脚气病

[11]Dutch[5dQtF]n.荷 兰 人,荷 兰 语

adj.荷兰的

[12]scrap[skrAp]n.碎片,废品堆放场

[13]polished[5pRliFt]ricen.精白米,上

白米

[14]coarsericen.糙米

[15]perpetuate[p[:5petjueit]vt.使永存,使不朽

犈狊狊犪狔33 犉狅狅犱狊犜犺犪狋犉犻犵犺狋犆犪狀犮犲狉

1.Preventionisalwayspreferabletoacure,andwhilemuchofthedataarestillpreliminary[1],agrowingbodyofevidencesuggeststhatthelocalgreenmarket[2]maybearichsourceofanticancer[3]agents.Inparticular,certainfruitsandvegetablesseemtohavepowerfultumorfightingpropertiesthatresearchersarejustbeginningtoappreciate[4]andtostudy.Asamplingofthecurrentcrop[5]offindings:

2.Tomatoes:scientistshavelongknownthatmenwhoeatcookedtomatoproductssuchaspastasauces[6]tendtohavelowerratesofprostatecancer.Untillastweek,however,

thedatawereanythingbutconclusive.Astudyreportedatlastweek’smeetingoftheAmericanAssociationforCancerResearchshowsthatdailydosesoflycopene[7],anantioxidant[8]thatripenstomatoesandgivesthemtheirredcolor,maynotonlypreventprostatecancerbutshrinkexistingtumorsaswell.Menwhotook30mgofthesupplement[9](thequantityfoundin2lbsoftomatoes)hadlowerlevelsofprostatespecificantigen—anindicatorofcellgrowth—andsmallertumors.

3.Soy:previousstudiesshowedthatwomenwhoeatsoyproductssuchastofu[10]andsoymilk[11]arelesslikelytodevelopbreastcancer.Butitwasneverclearwhy.Nowasmallstudyoftwodozenwomenmaypointtoananswer:soyseemstokeepcirculatinglevelsofestrogenlow,whichinturninhibitsbreastcellsfromproliferating.Womeninthestudydrankmorethanfourglassesofsoymilkadayforonemonth,andtheirpeakbloodlevelsofestrogendropped40%.

4.Broccoli[12]:amongallthecancerfightingvegetables,broccoli,cauliflower[13]andcabbagestandsout,especiallyincancersofthebladder[14].Regardlessofhowmanyfruitsandvegetablesagroupof48000menate,onlythoseconsumingbroccoliandrelatedcruciferousveggies[15]reducedtheirriskofbladdercancer,accordingtoareportintheJournaloftheNationalcancerInstitute.Broccolianditskinmayfightcancerbydetoxifyingorganismsinthegutthatwouldotherwisetriggermalignanciesinbladdertissues.

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 Notes

[1]preliminary[pri5limin[ri]adj.预 备

的,初步的

[2]greenmarketn.蔬菜市场

[3]anticancer[5Anti5kAns[]adj.抗 癌

[4]appreciate[[5pri:Fieit]vt.赏识,鉴

赏,感激vi.增值,涨价

[5]crop[krRp]n.一 些,大 量;农 作 物,产量,平头,短发vt.收割,修剪,种

植vi.收获

[6]pastasauce[5pB:st[sR:s]n.意大利面

[7]lycopene[5laik[7pi:n]n.番茄红素

[8]antioxidant[5Anti5Rksid[nt]n.抗氧化

[9]supplement[5sQplim[nnt]n.补充品

[10]tofu[t[UfU:]n.[日]豆腐

[11]soymilk[sRimilk]n.豆奶

[12]broccoli[5brRk[li]n.花茎甘蓝

[13]cauliflower[5kR:liflau[]n.花椰菜

[14]bladder[5blAd[]n.膀胱,气泡

[15]cruciferousveggie[krU:5sif[r[svedVi]n.十字花科蔬菜

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犝犖犐犜10 犕犗犔犈犆犝犔犃犚犅犐犗犔犗犌犢犃犖犇犜犚犃犖犛犌犈犖犐犆犛

犈狊狊犪狔34 犜犺犲犘狅犾狔犿犲狉犪狊犲犆犺犪犻狀犚犲犪犮狋犻狅狀(犘犆犚),狋犺犲犅犪狊犻犮狊

1.PolymeraseChainReaction(PCR)[1]isatechniqueforreproducingspecificDNAse

quencesinvitro.Thisprocess,inventedbyKaryMllisin1987,hasbeenautomatedforroutineuseinlaboratoriesworldwide.Theprocessiscarriedoutwithinamachinecalledthermocycler[2],anditcanproducemillionsorbillionsofcopiesofapieceofDNAinafewhours.

2.ThesequenceofPCRinvolvesthefollowingsteps:

A:TheDNAtobereproducedisheatedtoseparatethetwotemplate[3]strands.B:Twoprimers[4]whicharecomplimentarytotheregiontobeamplifiedareadded.C:AheatstableDNApolymeraseenzymeisalsoadded.Theenzymecatalysestheextensionoftheprimers,usingtheDNAstrandastemplate.

D:Thecycleisrepeated,withthenewlysynthesizeddoublestrandedDNAbeingheatdenatured[5]andtheenzymesextendingtheprimersattachedtotheliberatedsingleDNAstrands.

Thechainreaction,oncesetup,resultsintheexponentialamplification[6]oftheoriginalDNA,wherethenumberofcycles(n)determineshowmanycopiesoftheDNA(2n)areproduced.TheamountofamplifiedtargetY=X (1+efficiency)n,whereXistheinputcopynumber[7]andnthenumberofcycles.

3.APCRreactioniscomprisedof:(1)adoublestrandedDNA molecule:thisisthe“template”whichcontainsthese

quencetobeamplified.(2)primer(s):thisisasinglestrandedDNAmoleculewhichcananneal(bind)toaDNAsequenceinthetemplateDNAwhichhasthecomplementarysequence.

(3)dNTPs:amixturewithequalamountsofdATP,dTTP,dGTP,anddCTPwhicharethenucleotidesubunitswhichwillbeputtogethertoformnewDNAmoleculesinthePCRamplificationprocedure.

(4)TaqDNApolymerase[8]:theenzymewhichsynthesizesthenewDNAmoleculesusingthedNTPs.

4.HowPCRcanbeusedtodistinguishbetweentwodifferentDNAsequences?EachPCR

primeranneals[9]onlytoasequenceintheDNAtemplatewhichiscomplementarytoits

own.Ifprimer#1andprimer#2canannealtoGenomeA,thenPCRcanoccuranda

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DNAproductwillbesynthesizedinthePCRreaction.However,ifGenomeBdiffersfromGenomeAinthesequencetowhichprimer#2annealstotheDNA,thenPCRcannotoccursuccessfullyusingGenomeBDNAasatemplate,andnoDNAproductissynthesized.Thus,thispairofprimers(#1and#2)allowsustodistinguishbetweenGenomeAandGenomeB.GenomeAandGenomeBcanrepresentgenomicDNAfromtwoindividualsinthesamespeciesorpossiblyfromtwodifferentspecies.CertainportionsofgenomicDNAtendtoveryconserved[10](verylittlevariation)whileotherportionstendtovarygreatlyamongindividualswithinaspeciesoramongdifferentspecies.

5.ThetrickinsuchPCRanalysisisto:(1)findthosesequenceswhichhavejustenoughvariationtoallowustodetectdifferencesamongtheorganismsthatwearestudying;(2)findtherightPCRprimerswhichwillallowustodetectsequencedifferences.

6.TheapplicationsofPCRareextensive,someare:(1)AmplificationofsmallamountsofDNAforfurtheranalysisbyDNAfingerprinting[11].(2)TheanalysisofancientDNAfromfossils.(3)Mappingthehuman(andotherspecies)genome.(4)Isolationofa

particulargeneofinterest[12]fromatissuesample.(5)Detectionofmicroorganisms

presentinlownumbersinsoil,foodorwater.

 Notes

[1]Polymerase[5pRlim[7reis]ChainRe

action(PCR)n.聚 合 酶 链 式 反 应

(PCR)

[2]thermocycler[W[:m[U5saikl[]n.热

循环仪

[3]template[5templit]n.模板

[4]primer[5praim[]n.引物,初级读本,

雷管

[5]denature[di:5neitF[]vt.变性

[6] exponential amplification [7eksp[U5nenF[l7Amplifi5keiF[n]n.指数性

扩增

[7]inputcopynumbern.输入拷贝数

[8]TaqDNApolymerasen.TaqDNA聚

合酶。它是从一种水生栖热菌 (Ther

musaquaticus[W[:m[s[5kwAtik[s])

yT1株中 分 离 提 取 的。yT是 一 种 嗜

热真菌,能在70℃~75℃生长。该菌

是1969年从美国黄石国家森林公园火

山温泉中分离的。

[9]anneal[[5ni:l]n.退火,焖火,锻炼,

磨炼(意志)

[10]conserved[k[n5s[:vd]adj.保守的

[11]fingerprinting[5fiNg[5printiN]n.指

纹作图

[12]geneofinterestn.目的基因

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99   

犈狊狊犪狔35 犕犲狋犺狅犱狊狅犳犘犾犪狀狋犌犲狀犲犜狉犪狀狊犳犲狉

1.TheDNA(deoxyribonucleicacid)fromdifferentorganismsisessentiallythesame—

simplyasetofinstructionsthatdirectscellstomaketheproteinsthatarethebasisoflife.WhethertheDNAisfromamicroorganism,aplant,ananimalorahuman,itismadefromthesamematerials.

2.Throughouttheyears,researchershavediscoveredhowtotransferaspecificpieceofDNAfromoneorganismtoanother.

3.Aresearcher’sfirststepintransferringDNAisto“cut”orremoveagenesegmentfromachainofDNAusingenzyme“scissors”tocutataspecificsitealongtheDNAstrand.

4.Theresearcherthenusesthese“scissors”tocutanopeningintotheplasmid—theringofDNAoftenfoundinbacteriaoutsideofacell.Next,theresearcher“pastes”orplacesthegenesegment[1]intotheplasmid.Becausethecutendsofboththeplasmidandthegenesegmentarechemically“sticky”[2]theyattachtoeachother,formingaplasmidcontainingthenewgene.Tocompletetheprocess,researchersuseanotherenzymetopasteorsecurethenewgeneinplace.

5.Ourresearcherscontinuetoworkcarefullytoensurethatimprovedcropsarethesameascurrentcrops,exceptfortheadditionofonebeneficialtrait[3]which,forexample,

protectsthemfromaparticularinsectorvirus.6.AtMonsanto,researchersusetwomethodstointroducenewgenes,ortraits,intocrops.

Agrobacteriummethod7.Agrobacteriumisusedinbroadleafed(dicots)cropssuchastomatoes,potatoes,cottonandcanola[4]tointroduceanewgeneintoaplant.Agrobacteriumtumefaciensisasoilmicroorganismthatactsasanaturalgeneticengineer[5].ItcaninsertapieceofitsDNAintothechromosomeofaplantcell.Monsantoresearchersdiscoveredthatforsomekindsofplants,Agrobacteriumwastheperfectmethodforintroducingnewtraitsintotheplant.WhenpiecesofplanttissuewereaddedtoculturewiththeAgrobacteriumcontainingthenewgene,thegenecouldbetransferredintotheplantcells.Thesecellsgrowintoplantswiththenewtrait.

ParticleGun[6]

8.Forsomegrasslike(monocots[7])crops,suchascornandwheat,theAgrobacteriummethoddoesn’twork.Inthesecrops,researchersuseaparticleguntotransfergenes.Inthismethodmicroscopicpellets[8]ofgoldortungsten[9]arebathedintheDNAwiththenewtrait.Thepelletsarefiredfromthegunintotheplantcells.Astheparticlespassthroughthecell,someoftheDNAisleftbehind.TheDNAfromthepelletmixes

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withtheDNAofthecell,addingthenewtrait.

 Notes

[1]genesegment[5segm[nt]n.基因节段

[2]sticky[5stiki]adj.黏的,黏性的

[3]beneficialtrait[beni5fiF[ltreit]n.有

益性状

[4]canola[kA5n[Ul[]n.双低(低芥酸、低硫甙)油菜

[5]geneticengineern.遗传工程师

[6]particlegunn.粒子枪

[7]monocot[5mRn[Uk[Ut]n.单 子 叶 植

[8]pellet[5pelit]n.小球

[9]tungsten[5tQNst[n]n.[化]钨

犈狊狊犪狔36 犌犲狀犲狊犪狀犱犕狅狀犲狔—犘犪狋犲狉狀犻狋狔犜犲狊狋[1]

1.ThegrowingsensitivityandfallingcostofDNAtechnologycreatesaboom[2]marketfor

paternitytests.Notlongafterher19yearoldsonwasmurderedtwoyearsago,JoyceMcFieldofBroadview,Ill.(Illinoise),wascontactedbyawomanwhosaidshewas

pregnantwithhischild.McFieldwasinclinedtobelieveher,andwhenthebabygirlwasborn,shebecameadottinggrandmother.Nowandthen,however,shewonderedifthegirlwasreallyhergranddaughter.Soonedayshetookasampleofhisdeadson’

sbloodthatthepolicehadkeptasevidenceandhiredaHoustoncompanycalledIdenti

genetoconductaDNApaternitytest.“Ijustwantedtheretobenoquestionmarks,”

saysMcField.Thetestsshowedthatthelittlegirlwasnotherson’s;McFieldhassinceseveredrelationswithboththewomanandthechild.McFieldisoneofarapidlygrowingnumberofpeoplewho,inthepostO.J.[3],postMonica[4]world,aretakingadvantageoftherapidlyfallingcostsofDNAtestingtechnologytosettlelingering[5]paternityquestions.Andwherethere’sanewscienceandagrowingneed,there’ssuretobeacompanythatcomesalongtofillit.IntheDNAtestingindustry,Identigeneisit.

2.Thoughanestimated200000DNAprofiles[6]areruneachyearbystatestryingtodocument[7]childsupportorwelfarepayments,folks[8]withpaternityissuesrarelyhavethewherewithal[9]toorderupatestontheirown.Aboutfiveyearsago,however,thatstartedtochange.ItwasthenthatCarolineCaskey,32,aFrenchliteraturemajorturnedbusinessstudent,thoughttocombinecuttingedge[10]DNAanalysiswithold

fashioned,tohawk[11]theproductmarketing.Afewyearsearlier,alabheadedbyherfatherThomascaskeypatentedsomethingcalledthe“shorttandemrepeat”[12],ashortcutmethodofsamplingDNA.Caskeysawthenewtechniqueforthecashcow[13]itcouldbeandfoundedIdentigene,advertisingherfather’stechniqueasasimpleand—

at$475atestaffordablewaytoestablishpaternity,launchinganadblitz[14]thatin

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cludeddirectmail,TVtalkshowsandbillboards[15]in30U.S.cities,Caskeymadesureshegothercompanyinfrontoftheconsumers.

3.Consumersresponded.Identigene’sbusinesshasdoubledineachofthepastfiveyears.Thisyearthecompanyexpectstofield[16]67000telephoneinquiriesandconduct10,

000DNAtests,comparedwith650testsin1995.ItnowhasofficesinJapan,Korea,

BrazilandtheCzechRepublic.4.Thebusinessisnotwithoutcontroversy,however,mostofitcenteredontrickyquestionsofprivacy.ShorttandemtechnologyissosensitivethatitcanidentifyDNAfromlittlemorethanthesalivaresidueonasodacan.“Amoralprincipleingenetictestingisthatitshouldalwaysbedonewiththeconsentoftheindividual,”saysArthorCaplan,

directoroftheCenterforBioethics[17]attheUniversityofPennsylvania.“noonewantsotherssnooping[18]intohisDNA.”

5.Butsuchniceties[19]carrylittleweight[20]forpeopledesperatetoestablishsomethingasconsequential[21]aspaternity;andCaskeyplanstokeepcashingin[22]onthatneed.Identigeneispreparingtoofferanevencheaper,$150testthatwillprofile[23]newborns’DNAtoreassureanxiousparentsthatthey’releavingthehospitalwiththeirownchild.“It’spotentiallyamuchbiggermarketthanpaternitytesting,”saysCaskey.Anditisabiggerpayoff[24]too.

 Notes

[1]boom[bu:m]n.繁荣,隆隆声

[2]paternity[p[5t[:niti]testn.亲 子 鉴

[3]O.J.即OrenthalJamesSimpson美国

超级橄榄球星。1994年6月12日晚,

O.J.辛普森的前妻妮科尔和她的男朋

友罗 恩·戈 德 曼 被 杀,辛 普 森 成 为 唯

一的嫌疑犯被捕受 审。这 一 事 件 轰 动

了美国。1995年10月 美 国 洛 杉 矶 刑

事陪审 团 裁 定 辛 普 森 谋 杀 案 不 成 立,致使辛普森在长达1年多的 刑 事 官 司

中 胜 诉。这 一 事 件 再 一 次 轰 动 了 美

国。美 国 舆 论 将 此 称 为“世 纪 审 判”,当时使用了DNA检验。

[4]Monica即 MonicaSamilleLewinsky(莫妮卡·萨米勒·莱温斯 基)。由 于

20世纪90年 代 她 在 美 国 白 宫 实 习 时

和当时 美 国 总 统 比 尔·克 林 顿 发 生

性行为 造 成 绯 闻,从 而 引 起 公 众 的 注

意。起初克 林 顿 不 承 认,但 莫 妮 卡 衣

物上精子的DNA与克林顿的相同,克

林顿不得不承认。[5]lingering[5liNg[riN]adj.拖 延 的,

依依不舍的

[6]profile[5prEufail]n.剖面,侧面,外

形,轮廓

[7]document[5dCkjum[nt]vt.为……提

供证明,提供文件

[8]folks[f[uks]n.[口]父母

[9]wherewithal[5wZ[wi:5TR:l]n.(常

做thewherewithal)必要的资金

[10]cuttingedgeadj.有高度竞争力的

[11]hawk[hC:k]vt.捕 捉,咳 出,兜 售,(沿街)叫卖,散播

[12]shorttandem [5tAnd[m]repeatn.(生化)短的串联重复

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[13]cashcown.财源

[14]adblitz[blitz]n.广告闪电战

[15]billboard[5bilbC:d]n.广告牌

[16]field[fi:ld]vt.圆满答复

[17]bioethics[5bai[ueWiks]n.生 物 伦 理

[18]snoop[snu:p]vi.探 听,调 查,偷 窃

n.到 处 窥 视,爱 管 闲 事 的 人,私 家 侦

[19]nicety[5naisiti]n.准确,精密,细微

[20]carrylittleweight无足轻重

[21]consequential[7kRnsi5kwenF[l]adj.重大的

[22]cashinv.收到……货款,赚钱

[23]profile[5pr[Ufail]vt.给……画侧面

[24]payoff[5peiR:f]n.发工资,付清,盈

利,回报(=payback)

犈狊狊犪狔37 犌犲狀犲犌狌狀[1]犛狆犲犲犱狊犛犲犪狉犮犺犳狅狉犖犲狑犗狉犮犺犻犱[2]犆狅犾狅狉狊

1.AcorngeneisgivingUSDepartmentofAgriculture(USDA[3])researchersajumpstart[4]inverifyingwhatthecolorofanewflowerwillbe.

2.“Iforchidplantsarebredforanewcolor,it’sanyone’sguessabouttheoutcome.Usually,theplantindustrynowwaitsthreeyearsuntilabloomappears.”saidRobertJ.Griesbach,aplantgeneticistwithUSDA’sAgriculturalResearchService.

3.“Wefoundacorngenethatwillgiveusresultsonthecolorofnewhybridsinjustthreedays,”hesaid.Thatgeneregulatesthepigmentincornplants.

4.Griesbachsaidthegenetictechnique—coatingthecornDNAonmicroscopicgoldpelletsthatarepropelled,byaparticlegun,intoorchidflowerpetals—screenforgeneticflaws[5]intheparentplantscrossedtobreednewhybrids.

5.“Thatshouldgiveplantbreedersahigherdegreeofcertainty[6]incrossingvariousorchidcolorslikepurpleandyellowbycuttingdownonthenumberofunwantedcolormutations,”hesaid.Aboutoneinathousandorchidplantslacksadequatepigments,

causingwhiteornearwhiteflowers.Othermutationsresultinflowerswithvaryingde

greesofpurplepigment,rangingtoabout25percentoftruepurplecolor.6.“Wehavetestedthetechniquesuccessfullyonbulbplantslikegladiolas[7]andotherornamentals[8]likepetunias[9],aswellasonorchids,”saidGriesbach,anexpertonflowerpigmentation.“Geneticscreeningcouldresultinabroaderrangeofcolorsinorchidsandotherornamentalplants.”

7.Griesbachsaidthetechniquecouldbe“aboon[10]tobreedersoforchidsbecauseoftheflower’slonggenerationtime— uptosixyearsinsomecommercialtypes.”Orchidflowersarehighlyprized[11],headded,notingthatpottedphalaenopsisorchids[12]are“fastbecomingamajoreconomiccrop[13].”Griesbachtriedthefastergenetictechniqueafterremovingwhitepetalsfromorchidflowers.Hebombardedthepetalswithmicoscopic(1mmindiameter)goldpelletscoatedwithDNAtakenfromcornplants.

8.“ScreeningplantsforcolormutationsisanewusefortheparticlegunthatBobGries

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bachdemonstratedforthefirsttime”saidRogerLawson,NationalArboretum[14],

Washington,DC.“Thegoldpelletsweremorethan10timessmallerthanthedotattheendofthissentence.”Hesaid.Overmorethantwoyearsoftests,Griesbachfoundthattheintroducedcorngenescausenearwhiteflowerstogainpigmentswithin48hours.Onfullycoloredwildtypeflowers,thepurplecontinuedtodevelopforthenext24hours.“Eventually,theorchidcellswithcorngeneslookedthesameasthepurplecellsfoundinwildplants,withoutlossofpigment,”Griesbachsaid.

 Notes

[1]GeneGunn.基因枪

[2]orchid[5R:kid]n.[植]兰,兰花,淡

紫色

[3]USDAn.美 国 农 业 部(USDepartmentofAgriculture)

[4]jumpstartn.大起步

[5]geneticflaw[flR:]n.遗传瑕疵

[6]certainty[5s[:t[nti]n.确定,确实的

事情

[7]gladiola[glAdi5[ul[]n.剑 兰,唐 菖

[8]ornamental[7R:n[5mentl]n.装饰植

[9]petunia[pi5tju:nj[]n.牵牛

[10]boon[bu:n]n.恩惠,实惠,福利

[11]prized[praizd]adj.珍贵的,价高的

[12]phalaenopsisorchid[fAlA5n[upsisC:

kid]n.蝴蝶兰

[13]economiccropn.经济作物

[14]NationalArboretum[7B:b[:5ri:t[m]

n.国家植物园

犈狊狊犪狔38 犘犪狋犲狀狋犻狀犵犌犲狀犲犛犲狇狌犲狀犮犲狊:犖狅狋犻狀狋犺犲犅犲狊狋犐狀狋犲狉犲狊狋狊狅犳犛犮犻犲狀犮犲狅狉犛狅犮犻犲狋狔

1.TheAmericanbiotechnologyindustrywasshockedwhensocialactivist[1]JeremyRifkin

organisedapetitiondrive[2]lastyeartostirreligiousoppositiontoanypatentson“therichgeneticresourcesoftheEarth’sbiologicalcommons[3],”includingmostespeciallyhumangenes.BySeptemberhehadsecured[4]thesignaturesof186RomanCatholic,

Protestant[5],Jewish,Buddhist,Hindu[6],andMuslimAmericanreligiousleadersona

petitioncallingforabanonbiologicalpatents.Theindustryrespondedwithastronglyworded[7]whitepaperontheimportanceofallowingpatentsforhumangenes,whichisnowbeingcirculatedwidelyamongAmericanreligiousscholars.

2.Butdespitethereligiousbattleground,America’sdiscussionofpatents,outsidetheo

logical[8]circles,isnotablysecular[9].Itisconductedprimarilyintermsofpriorlegal

precedents[10]andtheimportanceofpatentprotectiontofurtherprivatesectorfundingandresearch.Thisisreflectedinthefightthathaseruptedbetweentwobehemoths[11]

inthepharmaceutical[12]community.

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3.SmithKlineBeechamhasformedaconsortium[13]withanAmericancompany,Human

GenomeSciences,tomap,sequence,andpatentasmuchofthehumangenomeaspossible.Theconsortiumhassequencedabout850000fragmentsofDNAdrawnfromalmost85%ofthehumangenome.Roughly200ofthe450applicationsforhumangene

patentsfiled[14]intheUnitedStatescomefromtheconsortium.

4.ButofficialsatthepharmaceuticalgiantMerckdonotbelievethatthebasicsequencein

formationofthehumangenomeoughttobepatentable[15].Somesuggestthatthecom

pany’soppositionisinspiredbythefactthat,unlikeSmithKline,ithasnotformedanalliancewithanotherfirmthatheldpatentspendingonalargenumberofgenese

quences.Whateverthecompany’smotives[16]theyhavearguedpersuasivelythatloc

kingupthebasicstructuralanddescriptiveelements[17]ofthegenomebynarrowlyheld

patentprotectionswillnotensurethatthehumangenomeismaximallyexploitedforthe

publicgood[18].

5.MerckisnowsponsoringagroupatWashingtonUniversityinStLouistosequencethehumangenomeandmaketheinformationfreelyavailable.Currently4000newse

quencesarebeingidentifiedeachweek.Asof[19]lastmonth,355000sequenceshad

beenidentifiedandplacedinadatabaseinthepublicdomain.Thishascreatedaremarkablesituationinwhichtwocorporategiantsareengagedinacompetitioninwhichoneseekstogiveawaywhattheotherwishestosell.

6.EventheUnitedStatesgovernmentcannotquitemakeupitsmindaboutpatentinghu

mangenes.In1991theNationalInstitutesofHealth(NIH)[20]filedapplicationsfor

2375partialDNAsequences.Uproarensued[21],includingunfavourablereactionsfrom

othergovernments,andinFebruary1994theinstitutes’director,HaroldVarmus,announcedthewithdrawalofapplicationsfortheseandothersequencepatents.

7.Meanwhilethegovernmentfiledandreceivedapatentonthegenesofamemberofthe

Hagahaitribe[22]inPapuaNewGuinea[23],someofwhomhaveanunusualresistanceto

leukaemia[24].Thissetoffaninternationalcontretemps[25],withThirdWorldnations

protestingagainstexploitationoftheirnationalgenomicresourcesbyavaricious[26]sci

entistsfromeconomicallyprivilegednations.8.Theargumentthatitisimmoraltopatenthumangeneticsequencesseemsunlikelyto

prevailfortworeasons.Firstly,whilestrongtheologicalreservationsexist,itishardtoequateassigningapatenttoaDNAstripwithownershipofahumanbody.Sellingbodiesintoslaveryisexploitative,becauseourpersonalidentityissointimatelytiedtoourbodies.Itisnotsoobviouslyaviolationofthehumanspirittoassignrightstoexclusiveuseanddevelopmentoverasegmentofchromosome13toagovernmentagencyorabiotechnologyconcern.Secondly,thegeneticspatenttrainhaslongsinceleftthestation.ItisalreadywidelyacceptedinAmericaandinmanyEuropeancountriesthat

genesofknownfunction,betheyhumanorotherwise,arepatentable.Sequencingofindividualgenesisseenasbeingakintodiscovering“nonnaturallyoccurringcomposi

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tionsofmatter,”andthereforemeetsthecriteriaforissuance[27]ofapatent— beingnew,useful,andnotobvious.

9.Ifthereisnopersuasivereasontoforbidthepatentingofhumangenes,theargumentmustturntoconsequences.Theissueisnolongerwhethergenescanbepatentedon

principle,butwhatsortofpatentsonwhatsortofgeneticinformationwillmostencouragethedevelopmentofusefulinventionsandproductsforpromotinghumanhealthandwellbeing.Whileaconvincingcasecanbemadeforthevalueofpatentsinsecuringinvestmentandattentionfromthosewhoholdthem,limitingaccesstoportionsofthehumangenometoasmallsetofscientistssimplybecausetheyidentifiedthesequencesfirstisunlikelytoleadtothemaximalintellectualexploitationofthisresource.Nordoesitmakemoralsense.Ifgovernmentfundshavebeenusedtomapandsequencethehumangenome,whyshouldthefruitsofthateffortbeturnedovertoasingleowner?

Permittingpatentsofsimplesegmentsofthegenome,ratherthanforproductsandinventions,wouldseemtobecontrarytothepublicinterest[28].

 Notes

[1]activist[5Aktivist]n.活动家

[2]petitiondrive[pi5tiF[ndraiv]n.请愿

运动

[3]biologicalcommonsn.生 物 学 共 有 资

[4]secure[si5kju[]vt.获得

[5]Protestant[5prRtist[nt]n.新教徒

[6]Hindu[5hindu:]n.印度教教徒

[7]stronglywordedadj.措辞强硬的

[8]theological[Wi[5lCddVik[l]adj.神

学的,神学上的

[9]secular[5sekjUl[]adj.世 俗 的,平 凡

[10]priorlegalprecedent优先的法律先例

[11]behemoth[bi5hi:mCW]n.(圣经)河

马,巨兽,庞然大物

[12]pharmaceutical[7fB:m[5sju:tik[l]n.药物adj.制药(学)上的

[13]consortiumn.社团,协会,联盟,(国

际)财团,[律]配偶的权利,(美)大学

联盟协定

[14]file[fail]vt.把……归档,提 出(申 请

等)[15]patentable[5peit[nteibl]adj.可 专 利

化的,可取得专利的

[16]motive[5m[utiv]n.动机,目的

[17]descriptive[dis5kriptiv]elementsn.描述性成分

[18]publicgoodn.公众利益

[19]asof:在……时,到……时为止从……

时起

[20]NIHn.(美国)国家卫生研究所(NationalInstituteofHealth)

[21]ensue[in5sju:]vi.跟着发生,继起

[22]Hagahaitribe:巴 布 亚 新 几 内 亚 的 一

个微小部族,该 部 族 最 早 于1983年 才

与外界有所接触。不久,美国的科学家

发现,他们的血液含有一种毒素。这些

科学家认为,此毒素可用来发展治疗白

血病的新方法。[23]PapuaNewGuinea:巴布亚新几内亚独

立国(TheIndependentStateofPapua

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NewGuinea)为 英 联 邦 国 家。位 于 太

平洋西南 部。西 与 印 度 尼 西 亚 的 伊 里

安查亚省接壤,南隔托雷斯海峡与澳大

利亚相 望。属 美 拉 尼 西 亚 群 岛。是 印

度洋和太 平 洋 上 最 后 一 片 未 被 污 染 的

净土。[24]leukaemia[ljU:5ki:mi[]n.白血病

[25]contretemps[5kC:ntr[t[:N]n.意外

事故,不合时宜,令人尴尬的事,不幸的

[26]avaricious[7Av[5riF[s]adj.贪财的,

贪婪的

[27]issuance[5iFu:[ns]n.发行,发布

[28]publicinterest公共利益

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犝犖犐犜11 犅犐犗犜犈犆犎犖犗犔犗犌犢

犈狊狊犪狔39 犘犾犪狀狋犜犻狊狊狌犲犆狌犾狋狌狉犲[1]

Introduction1.Planttissuecultureinvolvesthegrowingofplanttissuefromplantmaterialtakenfromasourceplant.Ithasbeenfoundthatplantscanreproducewholeplantsfromfragmentsofplantmaterialwhengivenanutrientmedia[2]capableofsupportinggrowthandappropriatehormonecontrol.

2.Thenutrientmediausedinplanttissuecultureisanagar[3]mediawithmacroandmicronutrients[4]dissolvedinit.Unlikeplantsgrowingfromaseed,tissueculturesrequireasupplyofcarboninanorganicformsuchassugars.Theyalsorequireaminoacids,Bvitaminsandgrowthhormones.Theconstituentsofthemediawillvarywiththeplantmaterialbeingcultured.

3.Planttissueculturecanbeusedtocloneplantsandproducemanyidenticalplantsforaparticularmarket.Thiscanbeusedwhenanewvarietyisgrownandothermethodsofcultivationaretooslowforthedesiredmarket.Itcanalsobeusedifastockplant[5]hasbeeninfectedandmaterialtakenfromtheplantthatisnotinfected.Theexcisedplantmaterialcanbegrownonandanydiseasefreeplantsgrownonforpropagation[6].Planttissuecultureisalsoofuseinresearchforbiochemists,geniticists,plantbreedersandplantpathologists[7].Planttissueculturehasalsoprovedmoreefficientintheproductionofsecondarymetabolites[8]thantheuseoftheparentplantsinvariousinstancesandhasbeenusedinthecommercialproductionofthenapthoquinonepigmentShikonin[9].Planttissueculturehasalsobeenusedintheproductionofflavours,sweeteners,naturalcolourantsandpharmaceuticals.Withtheadvent[10]ofgeneinsertion,plantcellswithgenematerialinsertedcanberegeneratedusingtissueculturetoproduceawholenewplant.Forexample,sugarbeetexplants[11]canbemicropropagated[12]toproducewholeplants.

4.Someplantsarebettersuitedtoplanttissueculturethanothersbutmostplantscanbecultivatedwithtimeandpractise.

MaterialsandMethods5.Whentakingplantmaterialtogrowonusingplanttissuecultureitisimportanttoget

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themostappropriatematerialfortheendproductyouareaimingfor.Planttissuehasbeenshowntobetotipotent[13],butdifferenttissueswillrequiredifferenttreatmentto

producewholeplantsifthatistheaim.Tissuethatisdividingsuchasatthenodesandleafaxils[14],leafpetiole[15]materialareoftenused.

6.Sharpcutswilldecreasetheamountofdecayingmaterialpresent,anddecreasethepossibilityofinfection.Theuseofasharpscalpel[16]isadvised.Forceps[17]arenecessarytomovetheplantmaterialtothegrowingmedia.Thecuttingshouldtakeplaceinasterileenvironmentandthegrowingmediaonlyexposedwhentheplantmaterialisplacedinit,afterwhichitshouldbesealed.

ForcepsScalpelDisinfectants[18]—forsurfaces,implementsandplantmaterial.LaminarFlowCabinet[19]

Bunsenburner[20]

Containerspetridishes,smallclearplasticcontainers,glassjars[21].GrowthmediaappropriatetoplantmaterialbeingculturedMurashigeSkoog[22]

Constituents                    Mediamg/LitreInorganicAmmoniumNitrate(NH4NO3) 1650PotassiumNitrate(KNO3) 1900CalciumChloride(CaCl2·2H2O) 440MagnesiumSulphate(MgSO4·7H2O) 370KH2PO4 170PotassiumIodide 0.83H3BO3 6.2ManganeseSulphate(MnSO4·4H2O) 22.3ZincSulphate(ZnSO4·7H2O) 8.6Na2MO4·H2O 0.25CopperSulphate(CuSO4·5H2O) 0.025IronSulphate(FeSO4·7H2O) 27.8Na2EDTA·2H2O 37.3Organic Inositol[23] 100

 NicotinicAcid[24] 0.5 Pyridoxine[25]HCl 0.5 ThiamineHCl 0.1 Glycine 2 Sucrose 3%BVitamins

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 Nicotinicacid ThiamineHCl PyridoxineHClGrowthHormones Auxins[26]

  BenzylAminoPurine[27]

  Indoleaceticacid[28]

  InositolCytokinins[29]

 Kinetin[30]

Forgrowing,planttissueculturesonasuitablesiteisrequiredwhichisclean,warm(20℃)andthereisadequatelight.

7.Thesourceoftheplantmaterialisimportantassomeplanttissueisbettersuitedtotissueculturethanothers,theabilityofplantmaterialtogrowanddivideinvitroisknownastotipotency[31],butdifferentplantmaterialwillneeddifferentcontroltoformnewplantmaterial.Theplantmaterialmayformanewembryo,callus[32]tissueorawholeplantdependingonhowitislookedafter.

HistoryofPlantTissueCulture8.Thisabilityhasbeenknownformanyyearsandmuchinformationhasbeengatheredonthebestwaystolookafterplantmaterialofdifferentspeciesandsourcesfordifferentusesusingplanttissueculture.Vochtungin1878observedthatcellsalongastemslengthwerecapableofgeneratingrootsorshoots.GottliebHaberlandt,aGermanbotanist,wasthefirsttogeneratenewtissuefromfullydifferentiatedtissue.

9.Hanniggrewnearlymatureembryosofcrucifersandgrewthemtomaturityonmineralsaltsandsugarsolution.Theembryoswouldnotgrowtoformplantshoweverwithouttheadditionofgrowthcompounds.Laterworkwassuccessfulingrowingonembryoswiththeadditionofcoconutmilk[33].Nutrientmediathenincludedmineralsalts,vitamins,aminoacids,andsugar.Laibachsuccessfullyrearedembryosthatwereotherwiseunviable[34]usingtissueculture.Severalnewhybridshavesince‘evolved’usingtissueculturethatwouldotherwisehavebeenunviableattheembryostage.

10.WhitesuccesfullyrearedtomatorootculturesusingamediumcontainingthreeBvitamins,pyrodoxine,thiamineandnicotinicacid,alsoinorganicsaltsandsucrose.Inthe1030’sidentificationofauxinasanaturalgrowthregulatorandtherecognitionoftheimportanceoftheBvitaminsledtoimprovementsintissueculturepractices.Proliferationofcellswasachievedusingasolutioncontainingglucoseandcysteinehydrochloride[35].Thefirstcontinuallygrowingcultureswereachievedusingcarrotrootcambium[36].

11.Celldivisionintissuehadtoawaitthediscoveryofkinetin.Thiswasfirstdiscoveredbyautoclaving[37]freshlyisolatedslurriesofDNAfromHerring[38]sperm.Thediscoveryof

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cytokininsgavemuchimpetus[39]totissueculture.12.Techniquesdevelopedtostimulatecelldivisioninliquidculture.In1965wholeplants

wereraisedfromisolatedsinglecellsbyfilteringsuspensionculturesandgrowingontheisolatedcellsonsolidmediacontaining0.6%agar.Thesetechniquesarenowwidelyusedforcloningtissues.

13.Hormonalcontroloftissueculturewasachievedusingtheregulationofcytokinin:auxinratio,thuscontrollingrootandshootdevelopmentintobacco.Itthenbecamepossibletomanipulatetissuesandtodevelopwholeplantlets[40]viashootandrootdevelopment.Cellscouldalsobecontrolledtoproducesomaticembryos[41]whichcanthenbeusedtoproducewholeplants.Rapidpropagation[42]oftissuesfromcalluswasusedthoughgeneticvariationintissueculturetendedtooccur.Productionfromshoottip[43]andleafprimordia[44]provedamoresuccessfultechnique.Thetechniquewasusedtoproducevirusfreeplants[45]frominfectedDahlias[46].Orchidswerealsoclonedonawidescaleandthetechniquewasadaptedforferns,foliageplants[47]andfruitplants.

14.Growingoncytokininrichmediacanreduceapicaldominance[48]leadingtomoreshootsandtoquickerregenerationofnumbers.Invitrofertilization[49]madeitpossibletocrossvarietiesunabletocrossinnature.Haploidplantsoftobaccowereraisedfrompollengrains.Amorerecentdevelopmentintissuecultureisprotoplast[50]culture.Thistechniquehasallowedthecrossingofplantsbyprotoplastfusion[51],somatichybrids[52]

havethusbeenproducedofNicotianaglauca× Nicotianalangsdorfii.15.Tissuecultureisthusprovingtobeusefulinavarietyofwaysincludingplantpropagation,raisingandmaintenaceofhighhealthstatusplants,germplasm[53]storage,andavaluabletechniqueinplantimprovement.Inplantimprovementtissueculturemaybeusedinthetechniqueofgeneinsertiontoimproveplantstocks.

16.Planttissueculturehasalsobeenusedintheproductionofsecondarymetabolitesinplants.Theproductionofflavours,sweeteners,naturalcolourants,aswellaspharmaceuticalshasallachievedusingtissueculture.

 Notes

[1]planttissueculturen.植物组织培养

[2]nutrientmedia[5nju:tri[nt5mi:dj[]

n.营养基

[3]agar[5eigB:]n.琼脂

[4]macroandmicronutrients大量和微量

营养

[5]stockplantn.母株

[6]propagation[7prRp[5geiF[n]n.(动

植物)繁殖,(声波,电磁辐射等)传播

[7]pathologist[p[5WRl[dVist]n.病理

学家

[8]secondarymetabolite[mi5tAb[lait]

n.次生代谢物

[9]napthoquinone[nApW[kwi5n[un]n.萘醌(即Shikonin:紫草素)

[10]advent[5Adv[nt]n.到来

[11]explant[eks5plAnt]n.外植体

[12] micropropagate [maikr[u 5prRp

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[5geit]v.微繁殖

[13]totipotent[t[u5tip[t[nt]adj.(细胞)全能的

[14]axil[5Aksil]n.叶腋

[15]petiole[5peti[ul]n.叶柄,柄部

[16]scalpel[5skAlp[l]n.解剖刀

[17]forceps[5fR:seps]n.镊子,钳子

[18]disinfectant[disin5fekt[nt]n.消毒剂

[19]LaminarFlowCabinet[5lAmin[fl[U5kAbinit]n.层流橱柜

[20]Bunsenburner[5bQnsn5b[:n[]n.本生灯(即煤气灯)

[21]glassjar(实验室用)玻璃缸,玻璃瓶

[22]MurashigeSkoogn.MS培养基

[23]inositol[i5n[Usit[Ul]n.肌醇

[24]nicotinicacid[7nik[5tinik5Asid]n.烟酸,尼克酸

[25]pyridoxine[7pi[ri5dRksin]n.吡哆醇

(维生素B6)[26]auxin[5C:ksin]n.生长素类

[27]6benzyl[5benzil]aminopurine6苄

氨基嘌呤

[28]indoleacetic[5ind[ul[5si:tik]acid吲

哚乙酸

[29]cytokinin[5sait[u5kinin]n.细胞分裂素

[30]kinetin[5kain[tin]n.激动素

[31]totipotency[t[J5tip[t[nsi]n.全能性

[32]callus[5kAl[s]n.愈伤组织,皮肤的

硬结组织,胼胝,老茧

[33]coconut[5k[Uk[nQt]milkn.椰奶

[34]unviable[Qn5vai[bl]adj.不能独立生

存的

[35]cysteinehydrochloride[5sistin7haidr[u5klR:raid]n.盐酸半胱氨酸

[36]cambium[5kAmbi[m]n.[植]形成层

[37]autoclave[5R:t[ukleiv]n.(烹 调 用)高压锅,高压灭菌器

[38]herring[5heriN]n.青鱼,鲱

[39]impetus[5impit[s]n.推动力,促进

[40]plantlet[5plB:ntlit]n.小植物,苗

[41]somaticembryo[s[U5mAtik5embri[u]n.体细胞胚胎

[42]rapidpropagation快繁

[43]shoottip茎尖

[44]leafprimordia[prai5mC:dj[]n.叶原

[45]virusfreeplant无病毒植株

[46]dahlia[5deilj[]n.[植]大丽花

[47]foliage[5f[uliidV]plantn.观叶植物

[48]apical[5Apik[l]dominancen.顶端优

[49]invitro [in5vi:tr[u]fertilizationn.体外受精

[50]protoplastn.原生质体

[51]protoplastfusion原生质体融合

[52]somatichybrid体细胞杂种

[53]germplasm [plAzm]n.[生]种 质,生

殖细胞的细胞质

犈狊狊犪狔40 犆犾狅狀犻狀犵犜犲犮犺狀犻狇狌犲狊

1.Whatiscloning?Whatarecloningtechniques?Cloningreferstothedevelopmentofoff

springthataregeneticallyidenticaltotheirparent.Animalswhichreproduceasexual

ly[1]areexamplesofclonesthatareproducednaturally.

2.Thankstoadvancesingenetics[2]however,cloningcanalsooccurartificiallybyusingcertaincloningtechniques.Cloningtechniquesarelaboratoryprocessesusedtoproduceoffspringthataregeneticallyidenticaltothedonorparent.

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3.Clonesofadultanimalsarecreatedbyaprocesscalledsomaticcellnucleartransfer[3].Therearetwovariationsofthismethod.TheyaretheRoslinTechniqueandtheHonoluluTechnique.Itisimportanttonotethatinallofthesetechniquestheresultingoffspringwillbegeneticallyidenticaltothedonorandnotthesurrogate[4],unlessthedonatednucleusistakenfromasomaticcellofthesurrogate.

CloningTechniquesSomaticCellNuclearTransfer4.Thetermsomaticcellnucleartransferreferstothetransferofthenucleusfromasomaticcelltoaneggcell.Asomaticcellisanycellofthebodyotherthanagermcell[5].Anexampleofasomaticcellwouldbeabloodcell,heartcell,skincell,etc.

5.Inthisprocess,thenucleusofasomaticcellisremovedandinsertedintoanunfertilizedeggthathashaditsnucleusremoved.Theeggwithitsdonatednucleusisthennurtured[6]anddividesuntilitbecomesanembryo.Theembryoisthenplacedinsideasurrogatemotheranddevelopsinsidethesurrogate.

TheRoslinTechnique6.TheRoslinTechniqueisavariationofsomaticcellnucleartransferthatwasdevelopedbyresearchersattheRoslinInstitute.TheresearchersusedthismethodtocreateDolly[7].

7.Inthisprocess,somaticcells(withnucleiintact)areallowedtogrowanddivideandarethendeprivedofnutrientstoinducethecellsintoasuspendedordormantstage.Aneggcellthathashaditsnucleusremovedisthenplacedincloseproximity[8]toasomaticcellandbothcellsareshockedwithanelectricalpulse.Thecellsfuseandtheeggisallowedtodevelopintoanembryo.Theembryoisthenimplanted[9]intoasurrogate.

TheHonoluluTechnique8.TheHonoluluTechniquewasdevelopedbyDr.TeruhikoWakayamaattheUniversityofHawaii.Inthismethod,thenucleusfromasomaticcellisremovedandinjectedintoaneggthathashaditsnucleusremoved.Theeggisbathedinachemicalsolutionandcultured.Thedevelopingembryoisthenimplantedintoasurrogateandallowedtodevelop.

WhyUseTheseTechniques?

9.Researchershopethatthesetechniquescanbeusedinresearchingandtreatinghumandiseasesandgeneticallyalteringanimalsfortheproductionofhumantransplantorgans.

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 Notes

[1]asexually[A5seksju[li]adv.无 性 地,无性生殖地

[2]geneticsn.遗传学

[3]somaticcellnucleartransfer体 细 胞 核

转移

[4]surrogate[5sQr[git]n.代理,代用品,代理人vt.使代理,使代替

[5]germcell生殖细胞

[6]nurture[5n[:tF[]n.养 育,教 育,教

养,营养品vt.养育,给予营养物,教养

[7]Dolly[5dCli]n.多莉(克隆羊)[8]proximity[prRk5simiti]n.接近,亲近

[9]implant[im5plB:nt]v.移植,植入

犈狊狊犪狔41 犎狅狑狋狅犆犾狅狀犲犪犎犲狉犱?

1.FirsttherewasDollytheScottishsheep.ThenlastJuly,cameseverallittersofclonedmice[1].NowscientistsatJapan’sKinkiUniversityhaveproducedsomethingevenbiggerandagooddealtastier:eightidenticalcalvesclonedfromasinglecow.

2.Writinginlastweek’sissueofScience,TheJapaneseresearchersreportthattheyachievedthisfeatofbovinephotocopyingusingtwodifferenttypesofcells,takenfromasinglecow’sovariesandfallopiantubes[2].Thosecells—allcarryingthesamegeneticpayload— wereintroducedintocowova[3]whosegeneshadbeenscoopedaway.Tensuchidenticalembryoswerethenimplantedinthewombsofsurrogatecowmothers,

andallbuttwocametoterm.3.NooneknowswhytheKinkiteammanagedtobat[4]8outoften(whileDolly’screatorsneeded29embryostogetonehit).Japanesescientistshopetolearnmorewhenothercalves—clonedfromliver,kidney,andheartcells—arebornnextspring.Thebeefindustryisanxiouslyawaitingtheanswer:theclonescomefromalineofprize[5]cowswhosemeatsellsfor$100apound.

 Notes

[1]mice[mais]n.小鼠(pl)[2]fallopian[fR:5l[UpjB:n]tuben.输卵

[3]ova[5[Uv[]n.卵(ovum的复数)[4]batvt.命中

[5]prizeadj.第一流的

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犈狊狊犪狔42 犆犾狅狀犲狊:犃狊犕犪狀狔犜狑犻狀狊犪狊犢狅狌犔犻犽犲

1.Whenagardener[1]wantstogrowanewplant,hecanoftentakeacutting[2]fromasingleparentplant.Fromonestemorleafhecangrowanentireplant.Intheanimalkingdom[3],ofcourse,weneedtwoparentsfortheproductionofaneworganism:wecannotcutoffatoe[4]andgrowababyfromit.ButinJune1966ateamofOxfordbiologistsannouncedinthemagazineNaturethattheyhadgrownsevenfrogsfromtheintestinalcellsofotherfrogs.Inotherwords,theyhadmanagedtousethegardener’stechniquewithananimal.

2.Basically,whattheydidwastoexchangethegenesinthefrog’scells.Theystartedoffwithafrog’segg.Theyremovedthenucleus,whichcontainsallthegenes,andreplaceditwiththenucleusfromabodycellofanotherfrog.Theythenimplantedtheeggwithitsnewnucleusinafemalefrogandcausedittostartdeveloping.Theeventualresultwasanormalfrog.Butbecausetheneweggnucleuscamefromanotherfrog’sbodycell,whichcontainsthecompletedoublesetofgeneticinstructionsofitsowner,thenewfrogwasgeneticallyidenticaltothatoriginalfrog.Itcontainednoneofitsmothers’genesatall,andnoneofthegenesfromtheoriginalegg.Ifonedoesthisseveraltimesusingthesamedonor,takingthenucleusfromthesame‘parent’,theresultisawholesetor‘clone’ofidenticaltwins.Theyarenotonlyidenticaltoeachother.Theyarealsoidenticaltotheirparent.

3.Thenextstepwastoclonelandanimalssuchassheepandcows.Thesurgeryinvolvedwasmoredelicate[5],fortheseanimalshavesmallereggswithtougherouterskins,butthetechniqueistechnicallyfeasible[6]inhumans.Sointheory,itispossibleforustoreproduceexactcopiesofourselves.Possible,perhaps,butisitlikely?

4.Agreatdealofnonsensehasbeenwrittenaboutthedangersofcloning.Wickedrulerscouldturnoutunlimitednumbersofidenticalpeopleandcreatearmiesofsoldiersorslaves.Butforfivethousandyearsithasbeenperfectlypossibleforpowermadrulerstopickoutcertainhumanbeingsandbreedthemselectively,creatingspecializedtypes,

justashumanshavebredcowsanddogs.Norulerhaseversucceededindoingso,becausenoneoftheirsubjects[7]wouldstandfor[8]it.Besides,ifonewantsaspecializedarmyofmen,itisfareasierandquickertotrainthem.Whatruler,howevermad,

wouldbewillingtowaittwentyyearsforhisarmytogrowup?

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 Notes

[1]gardenern.园丁

[2]cuttingn.切段

[3]animalkingdom 动物界

[4]toen.趾,脚趾,足尖

[5]delicateadj.脆弱的,微妙的,棘手的

[6]feasibleadj.可行的,切实可行的

[7]subject[5sQbdVikt]n.国民

[8]standfor忍 受;代 表;象 征,倡 导 或 者

支持

犈狊狊犪狔43 犛狋犲犿犆犲犾犾狊犪狀犱犜犺犲犻狉犝狊犲狊

Whatarestemcells?

1.Stemcells[1]areunspecialized[2]cellsthathavetwoimportantcharacteristicsthatdistin

guishthemfromothercellsinthebody.First,theycanreplenish[3]theirnumbersforlongperiodsthroughcelldivision.Second,afterreceivingcertainchemicalsignals,theycandifferentiate[4],ortransformintospecializedcellswithspecificfunctions,suchasaheartcellornervecell.

2.Stemcellscanbeclassifiedbytheextenttowhichtheycandifferentiateintodifferentcelltypes:Totipotentstemcells[5]candifferentiateintoanycelltypeinthebodyplustheplacenta[6],whichnourishestheembryo.Afertilizedeggisatypeoftotipotentstemcell.Cellsproducedinthefirstfewdivisionsofthefertilizedeggarealsototipotent.Pluripotentstemcells[7]aredescendantsofthetotipotentstemcellsoftheembryo.Thesecells,whichdevelopaboutfourdaysafterfertilization,candifferentiateintoanycelltype,exceptfortotipotentstemcellsandthecellsoftheplacenta.Multipotentstemcells[8]aredescendentsofpluripotentstemcellsandantecedentsofspecializedcellsinparticulartissues.Forexample,hematopoieticstemcells[9],whicharefoundprimarilyinthebonemarrow[10],giverisetoallofthecellsfoundintheblood,includingredbloodcells,whitebloodcells,andplatelets.Anotherexampleisneuralstemcells[11],

whichcandifferentiateintonervecellsandneuralsupportcellscalledglia[12].3.Progenitorcells[13](orunipotentstemcells[14])canproduceonlyonecelltype.Forexample,erythroidprogenitorcells[15]differentiateintoonlyredbloodcells.

4.Attheendofthelongchainofcelldivisionsare“terminallydifferentiated”[16]cells,

suchasalivercellorlungcell,whicharepermanentlycommittedtospecificfunctions.Thesecellsstaycommittedtotheirfunctionsforthelifeoftheorganismoruntilatumordevelops.Inthecaseofatumor,thecellsdedifferentiate[17],orreturntoalessmaturestate.

5.Researchisnowbeingconductedonbothadultandembryonicstemcellstodetermine

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thecharacteristicsandpotentialofbothtocuredisease.

Whatarethesourcesofstemcells?

6.Therearethreesourcesofstemcells:

Embryonicstemcells(ESCs)[18]arederivedfrom4to5dayoldembryos.Atthisstage,theembryosaresphericalandareknownasblastocysts[19].Eachblastocystconsistsof50to150cellsandincludesthreestructures:anouterlayerofcells,afluidfilledcavity,andagroupofabout30pluripotentcellsatoneendofthecavity.Thislattergroupofcells,calledtheinnercellmass[20],formallthecellsofthebody.

7.ESCculturesarecreatedinthelaboratorybytransferringtheinnercellmassfromablastocystintoaspeciallytreatedplasticculturedish.Thecellsdivideand,afterseveraldays,begintocrowdtheculturedish.Whenthishappens,thecellsareremovedand

plated[21]intoseveralfreshculturedishes.Thisprocessisrepeatedmanytimes,eventuallyyieldingmillionsofESCs.If,aftersixmonths,thecellskeepdividingwithoutdifferentiating,arestillpluripotent,andaregeneticallynormal,theyarereferredtoasanESCline[22].

8.TheblastocystsusedforcreatingESClinesarederivedfromeggsthatwerefertilizedininvitrofertilizationclinicsbutneverimplantedinawoman’suterus.Theresultingembryoswerefrozenandlaterdonatedforresearchpurposeswiththeinformedconsentofthedonors.Currently,thereareover400000unusedfrozenembryosinU.S.fertilityclinics.

9.BecauseESCsarepluripotentandrelativelyeasytogrowincellculture,theyareattractivecandidatesforuseinstemcelltherapies[23].However,justinjectingESCsintoasiteofinjurywouldprobablyresultinatumorgrowinginthatspot.ESCsmustfirstbedirectedtodifferentiateintothedesiredcells,suchasheartmusclecells,bloodcells,ornervecells.TocontrolESCdifferentiationincellcultures,scientiststrydifferenttechniques,suchaschangingthechemicalcompositionoftheculturemedium,alteringthesurfaceoftheculturedish,orinsertingspecificgenesintothecells.

10.OnepossibledrawbacktousingdifferentiatedESClinesinstemcelltherapiesisthatESCsfromonepersonmightillicitanimmuneresponsewhenplacedintoanotherperson,becausetheproteinsontheESCsurfacesmightbeviewedasforeignbytherecipient’simmunesystem.However,thisisfarfromcertain.ESCderivativeshavebeentransplantedbetweenspecies(forexample,pigstorats)withoutbeingrejected,sothepossibilityexiststhatESCderivativesfromonepersonmightbesafelytransplantedintoanotherperson.Studiesinvestigatingthishaveyettobedone.

11.Adultstemcellsareundifferentiatedcellsthatarefoundinsmallnumbersinmostadulttissues.However,theyarealsofoundinchildrenandcanbeextractedfromumbilicalcord[24]blood.Amoreaccuratephraseis“somaticstemcells[25],”althoughthisphrasehasyettobegenerallyadopted.

12.Theprimaryrolesofadultstemcellsinthebodyaretomaintainandrepairthetissuesin

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whichtheyarefound.Theyareusuallythoughtofasmultipotentcells,givingrisetoacloselyrelatedfamilyofcellswithinthetissue.Anexampleishematopoieticstemcells,

whichformallthevariouscellsintheblood.13.Recentevidence,however,indicatesthatsomeadultstemcelltypesmaybepluripotent,

oratleastabletodifferentiateintomultiplecelltypes.Forexample,hematopoieticstemcellscandifferentiateintoneurons,glia,skeletalmusclecells,heartmusclecells,

andlivercells.Whethertheyactuallydothisordinarilywithinthebodyisunknown.14.Bloodfromtheplacentaandumbilicalcordthatareleftoverafterbirthisarichsource

ofhematopoieticstemcells.Thesesocalledumbilicalcordstemcellshavebeenshowntobeabletodifferentiateintobonecellsandneurons,aswellasthecellsliningtheinsideofbloodvessels.

15.Apotentialadvantageofusingadultstemcellsfromapatientisthatthepatient’sowncellscouldbeexpandedinculture,treatedtodifferentiateintothedesiredcells,andthenreintroduced[26]intothepatient.Theuseofthepatient’sowncellswouldeliminateanypossibilitythattheymightberejectedbytheimmunesystem.Disadvantagesofusingadultstemcellsarethattheyarerareinmaturetissuesanditismoredifficulttoexpandtheirnumbersincellculture,comparedwithESCs.Embryonic(orfetal)germcellsarepluripotentstemcellsderivedfromsocalledprimordialgermcells[27],whicharethecellsthatgiverisetothegametes(spermandeggs)inadults.Scientistsobtain

primordialgermcellsfromtheareaina5to9weekoldembryo/fetusdestinedtobecomeeitherthetesticles[28]ortheovaries(thedividinglinebetweenembryoandfetusistheendofthe8thweek).LikeESCs,theprimordialgermcellsaretransferredintoaspeciallytreatedplasticculturedish,wheretheyformgermcellcolonies[29].

16.Lessresearchhasbeenperformedusingembryonicgerm(EG)cellsthanESCs,mostlybecausetheembryosusedforderivingEGcellsaredeliberatelyaborted[30],whiletheblastocystsusedforderivingESCsareproducedthroughinvitrofertilizationinafertilityclinic.EGcellsarealsodifficulttomaintainincellculturebecausetheyhaveatendencytodifferentiatespontaneously.

UsesofStemcells17.Upto128millionAmericansareaffectedbydiseasesforwhichresearcherslooktostemcelltechnologyforpromiseoftreatment.Whattheycurrentlyknowindicatesthatadultstemcellshavealimitedabilitytodifferentiateintousefultissues,fetalstemcellshaveagreatercapacitytodoso,andEScellsarethoughttobeabletodifferentiateintoanyotherkindofcell.Thedifferenttypesofcellsallhavepromisingapplications;hereisanoverview:

ChildhoodOnsetDiabetes[31]

18.InType1Diabetes,thecellsinthepancreasthatproduceinsulinareattackedbytheimmunesystem.Therehavebeenattemptstotreatitbytransplantingpancreaticcells,

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buttheimmunosuppressivedrugs[32]requiredtoperformthetransplantarehardforthebodytohandle,andthenumberoftransplantsavailableisverysmall.Stemcellscouldbeengineeredtodifferentiateintothebetacellsresponsibleforinsulinproduction,andtheycouldbemanipulatedtominimizethepossibilityofanimmuneresponsethatusuallyimpairs[33]transplants.

NervousSystemDiseases19.Therearecertaincellsinthebodythatreachmaturationandnolongeractivelydivide.

Nervecellsareanexampleofsuchcells.Therefore,ifthesecellsaredamagedordestroyed,thereisnorepairorreplenishmentoccurring.Thisisonedeterrentfromusingdrugs;theyareknowntodamageandkillcellsofthenervoussystem.Unfortunately,

peopleafflicted[34]withcertaintraumas[35]ordiseasestoofthenervoussystemsuchasmultiplesclerosis,Alzheimer’sdisease[36],Parkinson’sdisease[37],donothaveachoice.

20.Researchersseestemcellsasapotentialtreatmenttosuchdiseases.Forexample,participantsinParkinson’sstudieshaveshownsomeprogressafterfetalcellimplantationinpreliminarytrials.Studiesonrodents[38]havealsoproduceddesirableresultswhensubjectedtosimilarconditions.Perhapsatreatmentforsuchdebilitating[39]diseasesandinjuriesisinourfuture.

21.Evenincaseswhereactivelydividingcellsaredamaged,stemcelltreatmentisdesired.Indiseasesandinjuriesofthebonesandcartilage[40],ifdifferentiatedstemcellscouldbetransplantedintopatients,perhapslongtermdamagecouldbealleviated[41].Examplesarearthritis,bonefractures[42],andchondrodysplasia[43].

ImmunodeficiencyDiseases22.Notonlyhavestemcellsshownpromiseinnervoussystemtraumasanddiseases,buttheycouldpotentiallybeusedintreatmentofprimary(congenital)andsecondary(acquired)immunodeficiencydiseases[44].Thesediseasesarisewhenanimmunefunctionisunderdeveloped,suppressed,orabsent.ExamplesofsuchdiseasesareThymicaplasia(DiGeorgesyndrome)[45],WiskottAldrichsyndrome[46],andAIDS.Ifpluripotentstemcellscouldbetransplantedtopatientswithautoimmunediseases[47],theymaybeabletodirecttheimmunesystemtofunctionnormally.

Cancer23.Finally,stemcellscanbemanipulatedintobecomingbonemarrowstemcells.Suchcellsarecurrentlyusedintreatingpatientswithdeficiencies,suchaspostchemotherapy[48]

cancerpatientswithsomeeffectiveness.Futurestudiesareaimedatdevelopingtreatments,whicharemoresuccessfulinhopesofloweringsideaffectsfromchemotherapy.

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 Notes

[1]stemcell干细胞

[2]unspecialized[5Qn5speF[laizd]adj.未特化的

[3]replenish[ri5pleniF]v.补充

[4]differentiate[7dif[5renFieit]v.分化

[5]totipotentstemcelln.全能干细胞

[6]placenta[pl[5sent[]n.胎盘,胎座

[7]pluripotent[plJ[5rip[t[nt]stemcelln.多能(性)的干细胞

[8]multipotentstemcelln.多 效(性)的

干细胞

[9]hematopoietic [7hem[toU5pRitik]

stemcelln.造血的干细胞

[10]bonemarrow[5mAr[u]n.骨髓

[11]neuralstemcelln.神经干细胞

[12]glia[5gli:[]n.神经胶质

[13]progenitorcelln.起源细胞

[14]unipotent[ju5nip[t[nt]stemn.单能

性干细胞

[15]erythroid[5eriWrCid]progenitorcelln.红系造血祖细胞

[16]terminallydifferentiated终 极 分 化 了

[17]dedifferentiatevi.去分化

[18]embryonicstemcell(ESC)n.胚 胎 干

细胞

[19]blastocyst[5blAst[usist]n.胚泡

[20]innercellmassn.内细胞群

[21]platev.铺板

[22]ESClinen.胚胎干细胞系

[23]stemcelltherapy[5Wer[pi]n.干 细

胞治疗

[24]umbilical[7Qmbi5laik[l]cordn.脐带

[25]somaticstemcell体细胞干细胞

[26]reintroduce[5ri:7intr[5dju:s]vt.再

导入

[27]primordialgermcell原始生殖细胞

[28]testicle[5tesikl]n.睾丸

[29]colony[5kCl[ni]n.[生]群体

[30]deliberatelyaborted故意流产的

[31]ChildhoodOnsetDiabetesn.儿童期发

作糖尿病

[32]immunosuppressive[7imjun[us[5presiv]

drugn.免疫抑制药物

[33]impair[im5pZ[]v.削弱

[34]afflict[[5flikt]vt.使痛苦,折磨

[35]trauma[5trR:mE]n.外伤,损伤

[36]Alzheimer’sdiseasen.阿 尔 茨 海 默 病

(即老年痴呆)[37]Parkinson’sdiseasen.帕 金 森 氏 症,

震颤性麻痹

[38]rodent[5r[ud[nt]n.啮齿动物

[39]debilitate[di5biliteit]vt.使 衰 弱,使

虚弱

[40]cartilage[5kB:tilidV]n.软骨

[41]alleviate[[5li:vieit]vt.使(痛苦等)易于忍受,减轻

[42]bonefracture骨折

[43]chondrodysplasia[7kCndr[udis5pleizi[]n.软骨发育异常,软骨发育不良

[44]immunodeficiencydisease免疫缺陷病

[45]thymicaplasia[5Waimik [5pleizi[](DiGeorgesyndrome)胸腺发育不全,胸腺成形 不 完 全,胸 腺 先 天 萎 缩;DiGeorge综合症

[46]WiskottAldrichsyndrome WiskottAldrich综合症

[47]autoimmune[C:t[ui5mju:n]disease自体免疫疾病

[48]postchemotherapy [p[Jst 7kem[U5Wer[pi]adj.化疗后的

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犈狊狊犪狔44 犠犺犪狋犐犳犕狔犜犲狊狋犜狌犫犲犅犪犫犻犲狊犠犲狉犲犛狑犪狆狆犲犱[1]

犻狀狋犺犲犔犪犫?

1.MyheartgoesouttoDonnaFasano.She’stheNewYorkCitywomanwhowasreluctantlythrustintotheheadlines[2]lastweekbecauseofaninfertilitytreatment[3]mixedupthatimpregnated[4]herwithtwoembryos:onecreatedbyhereggandherhusband’

ssperm,theotherbyanAfricanAmericancouplewhohadbeenseeingthesamespecialistatthesametime.Shecarriedbothembryostoterm[5],givingbirthtotwobeautifulbutnoticeablydifferentboysandraisingthemforthreemonths,duringwhichtimetheysharedthesamecrib[6],thesameswing[7]andthesameparents.Thenwhenablackcouplecameforthclaimingtobethebiologicalparents[8]ofoneoftheirtwins,shefacedatrulySolomonic[9]testoflove.

2.Themindreels.Likethousandsofwomenmyage,I’mintimatelyfamiliarwiththeemotionalrollercoaster[10]ridethatisinvitrofertilization.Fouryearsago,myhusbandandIwereblessedwithourowntesttubebabies[11]beautifulgirltwinswhoareequallydelightfulbuttotallydifferent.Onelooksjustlikeme;theotherbearslittleresemblance.Aretheybothmine?Weremyeggsplacedintherightdrawer?IntherightPetridish?Fertilizedbytherightsperm?Issomeoneelseraisingoneofmychildren?Isignorancebliss?

3.Reproductivemedicinehascomealongwayinaveryshorttime.Itisnowa$1billionayearindustrythataccountsforsome23000livebirthsayearintheU.S.Butitswellpublicizedmishapshavemoralovertones[12].Areweinterferingwiththenaturalorderofthings,allowingdoctorstoplayGod?

4.Forthosewhochoosetoplayitsroulettewheel[13],babymakingtechnologyisbothheartwrenching[14]andexpensive(asmuchas$18000foraprocedure[15]).Itinvolvessophisticateddrugsthatyoumustinjectintoyourselfdailyandwhoselongtermtoll(cost)maybeyetunknown.Butthepossiblereturn?Amiracle!

5.LastweekFasanoannouncedshehadagreedtosurrender[16]custody[17]ofherblacksontotheblackcouple,pendingthefinalresultsofaDNAtest.Amotherwasgivingupasonwhomshehadborneandwhomsheloves;anotherwomanwasreceivingthegiftoflife.Twocoupleswhohadseparatelymadethedecisiontoundergotheinvasive[18]proceduresofmodernreproductivemedicineandplacetheirfaithinthehandsofalltoofallible[19]infertilityexpertsarenowpermanentlyjointogether,theirprivatelivespublic,

theirsonsforeverbrothers.

 Notes

[1]swap[swCp]n.v.交换 [2]headline[5hedlain]n.大字标题

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[3]infertilitytreatment[inf[5tiliti5tri:

tm[nt]n.不育治疗

[4]impregnate[5impregneit]vt.使怀孕,使受精,使充满,注入,灌输

[5]carry……toterm足月分娩

[6]crib[krib]n.婴儿床

[7]swing[swiN]n.秋千

[8]biologicalparents生物学父母

[9]Solomonic[5sCl[m[nik]adj.像Solomon那 样 需 要 智 慧 的。Solomon(?

~932BC)所 罗 门,以 色 列 国 王,在 位

期间,发 展 贸 易,以 武 力 维 持 其 统 治,使犹太达到鼎盛,以智慧著称。

[10]rollercoaster[5r[ul[5k[ust[]n.旋

转木马车;翻滚过山车,云霄飞车(一

种上有敞篷 的 小 型 车 厢 且 快 速 行 驶 的

有急转弯的大坡度高架轨道,尤指游乐

园中的乘坐装置)[11]testtubebabyn.试管婴儿

[12]overtone[5[uv[t[un]n.[音]泛 音,暗示,折光的色彩

[13]roulettewheel[ru:letwi:l]n.轮盘赌

[14]heartwrenching[5rentFiN]adj.绞

心般的

[15]procedure[pr[5si:dV[]n.疗 程,程

序,手续

[16]surrender[s[5rend[]vt.交出,放弃,使投降,听任

[17]custody[5kQst[di]n.保管,监护权

[18]invasive[in5veisiv]adj.入侵性的

[19]alltoofallible[5fAl[bl]adj.太 易 出

错的

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犝犖犐犜12 犌犈犖犗犕犐犆犛犃犖犇犘犚犗犜犈犗犕犐犆犛

犈狊狊犪狔45 犌犲狀狅犿犻犮狊

1.Genomicsisthestudyofanorganism’sgenomeandtheuseofthegenes.Itdealswiththesystematicuseofgenomeinformation,associatedwithotherdata,toprovideanswersinbiology,medicine,andindustry.

2.Genomicshasthepotentialofofferingnewtherapeutic[1]methodsforthetreatmentofsomediseases,aswellasnewdiagnosticmethods.Otherapplicationsareinthefoodandagriculturesectors.Themajortoolsandmethodsrelatedtogenomicsarebioinformatics[2],geneticanalysis,measurementofgeneexpression,anddeterminationofgenefunction.

History3.Genomicsappearedinthe1980sandtookoff[3]inthe1990swiththeinitiation[4]ofgenomeprojectsforseveralspecies.Therelatedfieldofgeneticsisthestudyofgenesandtheirroleininheritance.

4.Thefirstgenometobesequencedinitsentirety[5]wasthatofbacteriophageFX174(5,

368kb)in1980.ThefirstfreelivingorganismtobesequencedwasthatofHaemophilusinfluenzae[6](1.8Mb)in1995;andsincethengenomesarebeingsequencedatarapidpace.Aroughdraft[7]ofthehumangenomewascompletedbytheHumanGenomeProject[8]inearly2001amidmuchfanfare[9].

Thegrowthofthe“omics”

5.Theoriginaluseofthesuffix“ome”(fromtheGreekfor‘all’,‘every’or‘complete’)

was“genome”,whichreferstothecompletegeneticmakeupofanorganism.Becauseofthesuccessoflargescalequantitativebiologyprojectssuchasgenomesequencing,thesuffix“ome”hasbeenextendedtoahostofothercontexts.Theonlyother“ome”toshakeitsoriginasabuzzword[10]isproteome[11],thetotality[12]ofproteins(expressedgenesthataretranslated)inanorganism,tissuetypeorcell,andproteomics[13]isnowwellestablished.

Comparativegenomics[14]

6.Comparisonofgenomeshasresultedinsomesurprisingbiologicaldiscoveries.Ifaparti

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cularDNAsequenceorpatternispresentamongmanymembersofaclade[15],thatsequenceissaidtohavebeenconservedamongthespecies.EvolutionaryconservationofaDNAsequencemayimplythatitconfers[16]arelativeselectiveadvantagetotheorganismsthatpossessit.Conservationalsosuggeststhatsequencehasfunctionalsignificance[17].Itmaybeaproteincodingsequenceorregulatoryregion.ExperimentalinvestigationofsomeofthesesequenceshasshownthatsomearetranscribedintosmallRNAmolecules,althoughthefunctionsoftheseRNAswerenotimmediatelyapparent.

7.Theidentificationofsimilarsequences(includingmanygenes)intwodistantlyrelatedorganisms,butnotinothermembersofoneoftheclades,hasledtothetheorythatthesesequenceswereacquiredbyhorizontalgenetransfer[18].Thisphenomenonismostprominentinthermophilicbacteria[19],whereitseemsthatgenesweretransferredfromArchaea[20]toEubacteria[21].Ithasalsobeennoticedthatbacterialgenesexistineukaryoticnucleargenomesandthatthesegenesgenerallyencodemitochondrialandplastidproteins,givingsupporttotheendosymbiotictheoryoftheoriginoftheseorganelles.

Geneticsimilarity[22]

8.ItisoftenstatedthataparticularorganismsharesXpercentofitsDNAwithhumans.Thisnumberindicatesthepercentageofbasepairsthatareidenticalbetweenthetwospecies.Hereisalistofgeneticsimilaritytohumans,withsources,whereknown.Whilethesenumberscomefromvarioussecondarysources,thedatamayhaveoriginatedfrommeasuresofDNADNAhybridizationorfromdirectsequencecomparisons.

Species Similarity Source

Human

Chimpanzee[23]

Bonobo[25]

Gorilla

Mouse

Dog

C.elegans

Banana

Daffodil

99.9%quotedbyPresidentClinton,Jan2000,StateoftheUnionaddress;

alsoHumanGenomeProject

100% identicaltwins

98.4%sources:AmericansforMedicalProgress;JonEntineintheSan

FranciscoExaminer

98.7% RichardMuralofCeleraGenomics,quotedonMSNBC[24]

equaltochimpanzee

98.38%basedonstudyofintergenicnonrepetitiveDNAinAmJHumGen

et.(2001)Feb;682:444~456

98% source:AmericansforMedicalProgress

85% comparingallproteincodingsequences,NHGRI[26]

95% JonEntineintheSanFranciscoExaminer

74% JonEntineintheSanFranciscoExaminer

50% source:AmericansforMedicalProgress

35% StevenRoseinTheGuardian22Jan2004

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 Notes

[1]therapeutic[Wer[5pju:tik]adj.治疗

的,治疗学的

[2]bioinformatics[bai[u5infR:5mAtiks]

n.生物信息学

[3]takeoffv.起飞

[4]initiation[i7niFi5eiF[n]n.开始

[5]entirety[in5tai[ti]n.全部,完全

[6]Haemophilusinfluenzae[hem[5filEsinfljU:enzB:]流感嗜血杆菌

[7]roughdraftn.框架图

[8]HumanGenomeProject人类基因组计

划 (HGP)[9]fanfaren.喇 叭 或 号 角 嘹 亮 的 吹 奏 声,

吹牛

[10]buzzword[bQzw[:d]n.时髦词汇

[11]proteome[5pr[uti[um]n.蛋白组

[12]totality[t[u5tAliti]n.全体,总数

[13]proteomics[5pr[uti5[umiks]n.蛋 白

组学

[14]comparative[k[m5pAr[tiv]genomicsn.比较基因组学

[15]clade[kleid]n.[生]进化支,分化支

[16]confer[k[n5f[:]vt.授予(称号、学 位

等),赠与,把……赠与,协议

[17]functionalsignificance功能意义

[18]horizontalgenetransfer水平基因转移

[19]thermophilic[7W[m[5filik]adj.嗜

热的

[20]archaea[B:5ki:[]n.古细菌

[21]eubacteria[5jU:bAk5ti[ri[]n.真 细

菌(即bacteria细菌)[22]geneticsimilarity遗传相似性

[23]chimpanzee[5tFimp[n5zi:]n.黑猩猩

[24]MSNBC:是 一 个 综 合 性 的24小 时 新

闻频道以及在线新闻服务供应商,创立

于1996年7月15日,是 由 微 软(MS)与NBC(国家广播公司)联合创立的。

[25]bonobo[5b[un[7b[u]n.(产于非洲刚

果河以南的)倭 黑 猩 猩[源 自 非 洲 当 地

语][26]NHGRI:美 国 人 类 基 因 组 计 划 研 究 所

(The NationalHuman GenomeResearchInstitute,NHGRI)

犈狊狊犪狔46 犚犻犮犲犌犲狀狅犿犲犠狅狉犽犆狉犲犪狋犲狊犎狅狆犲

1.Accordingtocolumnist[1]SmithfromCNNEWS[2]Science,thesequencingoftherice

genomewhichmayturnouttobeevenmoreimportantthanthesequencingofthehumangenomeinsomewaysaspassedalmostunnoticedSmithsaysthatbecauseofgeneticsimilarities,discoveriesmadeusingthericegenomewilltranslatewitheasetowheat,

barley,sorghum[3],millet[4]andahostofothers.Wemight,infact,begintospeakof

acerealgraingenome.Intheshortterm,though,itisricethatwillbeimportant,be

causericefeedsaninordinate[5]numberofus.Since1965,infact,theworld’sricepro

ductionhasbeengrowingat2.5percentayearenoughtokeeppacewithhumanity’s

hungrybellies[6].

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2.Thatmiracle,saysSmith,hasbeenwrought[7]usingstandardbreedingtechniquestoproducehighyieldvarieties.(Betterirrigationandincreasedaccesstocreditalsoplayedarole,accordingtotheInternationalRiceResearchInstitute,IRRI[8]).

3.Butstandardbreedingisyourclassicalblackbox.Youcrosssomeplants,observetheircharacteristicsandthencrosssomemore,hopingtocomeupwithanimprovement.Youdon’tknowwhat’sgoingoninsidetheplant.

4.Intheshortterm,saysSteveBriggs,knowingthericegenomewillletstandardbreederspeepinsidetheblackbox[9]andguidetheireffortsmoreefficiently.

5.BriggsisheadoftheTorreyMesaResearchInstitute[10]inLaJolla,Calif.,which,fortherecord,sequencedthericegenome.Alsofortherecord,theTorreyMesaResearchInstituteisthegenomicsresearchcenterforacompanycalledSyngenta,whichwasformedlastNovemberwhenNovartisAgribusinessandZenecaAgrochemicalsmerged.

6.SoSmithsayshecanhearthisnow.Onemorebiginternationalbiotechcompanyhasaproprietorial[11]interestinsomethingofvitalinteresttosmallfarmersinAsia.Timetobreakouttheplacards[12]andthetomatofish[13]suit.ButSyngentahaslearnedalessonortwofromthepastfewyears.Thericegenomewillbeavailablewithoutfeesorroyalty[14]paymentstoresearchcentersintheThirdWorld.Itwillalsobeavailablefreetoacademicscientists.

7.Now,ricebreedersintheThirdWorldwillhaveapowerfulnewtoolattheirdisposal.Forthefirsttime,Briggssaid,theywillknowatthelevelandwhat’sgoingonwhentheymakeacross.And,withanyluck,theymaybeabletocomeupwithvarietiesthatwillcontinuetofillthebillionsofstomachs.

8.BriggsaddsthatSyngentaalsohopesthatthenewknowledgewillallowitsownplantbreederstoimprovecerealcropseithernutritionallyorintermsofyieldandthoseimprovementswouldbeforsale.Inthelongrun,Briggswascitedassaying,Syngentahopestomatchgenetotraitsinaprocesscalledgenomicswithsufficientaccuracythatbiotechtoolscantakeoverfromtraditionalplantbreeding.Soinsteadofcrossingplantsandintheprocessmixingupthegenes,thebiotechnicians[15]wouldmanipulatethegenesdirectly.

 Notes

[1]columnist[5kRl[mnist]n.专栏作家

[2]CNNEWSn.美国有线电视新闻

[3]sorghum[5sR:g[m]n.高粱

[4]millet[5milit]n.小米

[5]inordinate[in5R:dinit]adj.过 多 紊

乱的

[6]humanity’shungrybelly人 类 饥 饿 的

肚皮

[7]wrought[rR:t]adj.work的 过 去 式

和过 去 分 词;做 成 的,形 成 的,精 炼

的,[冶](金属)锻造的

[8]InternationalRiceResearchInstitute.IRRI国际水稻研究所

[9]blackboxn.黑箱

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[10]TorreyMesaResearchInstituten.美

国托雷梅萨研究院

[11]proprietorial[prRprai[5tR:ri[l]adj.所有权的

[12]placard[5plAkB:d]n.布告,张贴

[13]tomatofishn.番茄鱼

[14]biotechnician[bai[5tekniF[n]n.生物

工程学家

犈狊狊犪狔47 犛犮犻犲狀狋犻狊狋狊犆狉犪犮犽犌犲狀犲犆狅犱犲狅犳犚犻犮犲

1.Scientistshavedecodedthegeneticblueprintofrice,astaple[1]forhalftheworld’spop

ulation,inabreakthroughthatcouldleadtohardiervarietiesandeasemalnutrition[2],

researcherssaidFriday.Italsocouldspeedresearchonmorecomplexgrainssuchascornandwheat.Riceisthefirstplantimportanttoagriculturetohaveitsgenomemapped.Itsmodelissimple,butitalsoissosimilartoothergrainsthatscientistscanusethericemaptolocategenesinthosecrops.Thatwouldmakeiteasiertoaddnutrientstocropsormakethemmoreresistanttodroughtandpeststhroughconventionalbreedingorgeneticengineering.“Identifyingnotonlythegenes,butalsotheirfunctionsandhowtheywork,willprovideresearcherswithcrucialnewknowledgetoim

provefoodcrops”,saidSteveBriggs,presidentoftheTorreyMesaResearchInstitute,

asubsidiary[3]ofSwitzerlandbasedSyngenta.2.TheprojectwasajointeffortofSyngentaandMyriadGeneticsInc.ofSaltLakeCity.ThebiotechcompaniesarefinishingaheadofaninternationalricegenomeprojectbasedinJapanthatisusingdifferentmappingtechniquesandresearchfunddonatedbySyn

gentarivalMonsantoCo.Thetwoprojectshavefollowedsimilartrackstorivalpublicandprivateeffortstodecodethehumangenome.Theinternationalriceproject,tobefinishedin2003,issupposedtobemoreaccurateandcomplete.Syngenta’sprojectmayraisequestionsaboutcorporatecontrolofgeneticmaterial,particularlybecauseitinvolvesacropthatisvitaltomanypoornations.

3.Thetwocompaniessaidtheywouldmakethericedataavailabletootherresearchersthroughresearchcontracts.Syngentasaiditalsowouldworkwithresearchinstitutesin

poorcountriestohelpfarmers.Thecompany’spolicyistoprovidedata,suchasthe

geneticcodeforrice,withoutroyalties[4]orfeeswhenitisusedforresearchbenefitingpoorfarmers.“IfSyngentafulfillsthatpolicy,poorfarmersmayreapsubstantialbenefits,”saidPerterPinstrupAndersen,directoroftheInternationalFoodPolicyResearchInstitute.Hecautioned[5],however,that“itwilltakemanyyearsofscientificstudybeforetheseadvancesreachthefieldsofsmallscalefarmers.Thesoonertheseeffortsareunderway,thebetter”.

4.Datafromtheinternationalprojectwillbefreelyavailabletoscientistsworldwide.Riceisarelativelypoorsourceofmanyessentialnutrients,butscientistsaredevelopingvarietiesenhancedwithvitaminAtopreventblindnessinAsianchildren.Hardiervarieties

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alsoareneeded.Riceproductionhasdoubledinthepast30yearsbutisnotexpandingenoughtokeeppacewithmanycountries’populationgrowth.

5.Lastyear,scientistscompletedthemappingofanotherplant,arabidopsis[6],butthericegenomeismoresimilartoothergrasses,includingwheat,cornandbarley,thattogetherwithricearetheworld’smainsourcesoffoodandanimalfeed.Riceplantshave12chromosomescontainingabout50,000differentgenes,whichinturnmakeupabout430millionbasepairsofDNA.Thewheatgenomeis37timeslarger,butrecentresearchhasfoundthatgrassgenomeshavesimilargeneticmapsoverlargeblocksofthechromosomes.Awheatbreedercouldusethericemaptofindasimilargeneinwhichtomakethatcropresistanttofungus,amajorpesttofarmers,saidBenjaminBurr,aplantgeneticistattheBrookhavenNationalLaboratoryinNewYork.

 Notes

[1]staple[5steipl]n.主粮作物

[2]malnutrition[5mAlnju:5triF[n]n.营

养不良

[3]subsidiary[s[b5sidj[ri]adj.辅 助 的,补充的n.分支机构

[4]royalty[5rRi[lti]n.使用费,版税 ,专利权税

[5]caution[5kR:F[n]n.小心,谨慎,警

告vt.警告

[6]arabidopsis[[5rAbi5d[Upsis]n.拟南芥

犈狊狊犪狔48 犌狉犪犻狀狊狅犳犎狅狆犲

1.Atfirst,thegrainsofricethatIngoPotrykussiftedthroughhisfingersdidnotseemat

allspecial.Butoncetheirdark,crinklyhusks[1]werestrippedawayandtheinteriors

polishedtoaglossysheen,Potrykuscouldbehold[2]theseeds’goldensecret.Attheir

core,thesegrainswerenotthepearlywhiteofordinaryricebutaverypaleyellowcour

tesy[3]ofbetacarotene[4],thenutrientthatserves,asabuildingblockforvitaminA.

Potrykuswaselated.Formorethanadecadehehaddreamedofcreatinggoldenrice[5]

thatwouldimprovethelivesofmillionsoftheworld’spoorestpeople.Atleast1millionchildren,weakenedbyvitaminA deficiency,dieeveryyearandanadditional350,000goblind.Potrykussawhisriceasthemodeststartofanewgreenrevolution:

bananasthatwouldn’trotonthewaytomarket,cornthatcouldsupplyitsownfertilizer,wheatthatcouldthriveindroughtriddensoil.Butimaginingagoldenricewasonething,Potrykusfound,andbringingoneintoexistencequiteanother.Yearafteryear,

heandhiscolleaguesranintounexpectedobstacles,beginningwiththefinicky[6]grow

inghabitsofthericetheyhadtransplantedtoagreenhouse[7]nearthefoothillsoftheSwissAlps.Andwhensuccessfinallycameinearly1999,Potrykus,65andaboutto

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retireasaprofessorattheSwissFederalInstituteofTechnologyinZurich,facedevenmoreformidablechallenges.Thegoldenricethatheandhiscolleaguesdevelopedisa

productofgeneticengineering,whatopponents[8]callFrankenfood[9].Assuch,itwasentangled[10]inawebofhopesandfearsandpoliticalbaggage[11],nottomentionafistfulofironclad[12]patents.

2.ForaboutayearnoweversincePotrykusandhischiefcollaborator,PeterBeyeroftheUniversityofFreiburginGermany,announcedtheirachievement,theirgoldengrainhasilluminatedanincreasinglypolarized[13]publicdebateovergeneticallyengineeredcrops.LastmonthPotrykusandBeyerarrivedinthePhilippinescarryinggoldenriceseedsandgeneticmaterialboundforIRRI.ThegoalofIRRIscientistswillbetodevelopgoldentropicalrice,basedonthetechniquesPotrykushasusedforhistemperatericevariety.Andthisisonlythefirststep.Twoprivatecompanies,SwissbasedSyngentaandMyriadGeneticsofSaltLakeCityintheU.S.revealedlastweekthattheyhavemappedtheentirericegenome,pavingthewayforotherdramaticbreakthroughs.Yearsoflabworkonaviablegeneticallymodified(GM)ricevarietyarestillneeded,

butscientistsinAsiawillundoubtedlyfindtheirricesubjectedtothesamekindofhostilesuspicionandscrutiny[14]thathasalreadyledtocurbs[15]onthecommercializationofthesecropsinBritain,Germany,SwitzerlandandBrazil.

3.Theincreasinglyacrimonious[16]debateovergeneticallyengineeredcropseruptedthemomenttheymadetheircommercialdebut[17]inthemid1990s.Europeanenvironmentalists[18]andconsumeradvocacygroups[19]werethefirsttolaunchmajorproteststhathavesincespreadworldwide.EnvironmentalistsinIndiahavefiledsuitagainstMonsantotopreventitfromtestinggeneticallymodifiedcotton.InthePhilippines,farmershavedemonstratedagainstseedgiantsMonsantoandDupont’sfieldtestsofBtcorn.AndactiviststherepointtoMiracleRiceproductoftheGreenRevolutioninthe’60sisacautionarylesson.ItswholesaleadoptioninSoutheastAsialedtoaricemonoculture[20],makingcropsmorevulnerabletoinsectpestsanddisease,andmoredependentonpesticides.Publichostilityisunderstandable.Mostofthegeneticallyengineeredcropsintroducedsofarrepresentminorvariationsonthesametwothemes:resistancetoinsectpestsandtoherbicidesusedtocontrolthegrowthofweeds.Andtheyareoftenmarketedbylarge,multinationalcorporationsthatproduceandselltheveryagriculturalchemicalsfarmersaresprayingontheirfields.SowhilemanyfarmershaveembracedsuchcropsasMonsanto’sRoundupReadysoybeans,withtheirgeneticallyengineeredresistancetoMonsanto’sRoundupbrandherbicide,thatletthemsprayweedkillerwithoutharmingcrops,consumershavecometoregardsuchthingswithmountingsuspicion.Whyresorttoastrangenewtechnologythatmightharmthebiosphere,

theyask,whenthebenefitsofdoingsoseemsmall?Indeed,thebenefitshaveseemedsmalluntilgoldenricecamealong.Goldenriceisthefirstcompelling[21]exampleofa

geneticallyengineeredcropthatmaybenefitnotjustthefarmerswhogrowitbutalsotheconsumerswhoeatit.Nowondersomanyofthoseconcernedaboutpovertyand

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hungerareconvincedthatsuchcropshaveacriticalroletoplayinfeedingtheworld.China,oneofthefirstcountriestogrowgeneticallyengineeredtobaccoandcottoncommercially,isinvestingheavilyinthetechnologyasawaytocombatitschronicdomesticfoodproblems.C.S.Prakash,ascientistattheCenterforPlantBiotechnologyResearchatTuskegeeUniversityinAlabama,recentlyaccusedantiGMactivistsofbeing“wellfedfolk[22]”who“jet[23]aroundtheworld”todisrupttechnologythatwillbenefitthepoor.AccordingtoPrakash“Biotechnologyisoneofthebesthopesforsolvingfoodneedwhenwehave6billionpeopleandcertainlyinthenext30to50yearswhentherewillbe9billionontheglobe”.

4.Indeed,bytheyear2020,thedemandforgrain,bothforhumanconsumptionandforanimalfeed,isprojectedtogoupbynearlyhalf.Addtothattheneedtoconserveoverstressedwaterresourcesandreducetheuseofpollutingchemicals,andtheenormityofthechallengeisapparent.

GoingFortheGold5.Inthelate1980s,afterhebecameafullprofessor[24]ofplantscienceattheSwissFederalInstituteofTechnology,IngoPotrykusstartedtothinkaboutusinggeneticengineeringtoimprovethenutritionalqualitiesofrice.Ofsome3billionpeoplewhodependonriceastheirmajorstaple,around10%risksomedegreeofvitaminAdeficiencyandthehealthproblemsthatresult.TheprobleminterestedPotrykusforanumberofreasons.Forstarters,hewasattractedbythescientificchallengeoftransferringnotjustasingle

gene,asmanyhadalreadydone,butagroupofgenesthatrepresentedakeypartofabiochemicalpathway.Hewasalsomotivatedbyempathy[25].AsachildgrowingupinwarravagedGermany,Potrykusandhisbrotherswereoftensodesperatelyhungrythattheyatewhattheycouldsteal.

6.Around1990,PotrykushookedupwithGaryToenniessen,directoroffoodsecurityfortheRockefellerFoundation.ToenniessenhadidentifiedthelackofbetacaroteneinpolishedricegrainsasanappropriatetargetforgenescientistslikePotrykustotacklebecauseitlaybeyondtheabilityoftraditionalplantbreedingtoaddress.Forwhilerice,

likeothergreenplants,containslighttrappingbetacaroteneinexternaltissues,itdoesnotproducebetacaroteneinitsendosperm (thestarchyinteriorpartofthericegrainthatmostpeopleeat).

7.AtaRockefellersponsoredmeeting,PotrykusmettheUniversityofFreiburg’sPeterBeyer,anexpertonthebetacarotenepathwayindaffodils.Theydecidedtocombinetheirexpertise.In1993,withsome$100,000inseedmoneyfromtheRockefellerFoundation,PotrykusandBeyerlaunchedwhatturnedintoasevenyear,$2.6millionproject,backedbytheSwissgovernmentandtheEuropeanUnion.“Iwasinaprivilegedsituation,”reflectsPotrykus,“becauseIwasabletooperatewithoutindustrialsupport.Onlyinthatsituationcanyouthinkofgivingawayyourworkforfree.”Thetwoscientistssoondiscovered,however,thatgivingawaygoldenricewasnotgoingto

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beeasy.Thegenestheytransferredandthebacteriatheyusedtotransferthosegeneswereencumberedbypatentsandproprietaryrights.OnlyafterextensivenegotiationshavethetwoscientistsmanagedtostrikeadealwithSyngenta,MonsantoandthefourothercompaniesthatheldexclusivelicensestothetechnologiesusedbyPotrykusandBeyertocreategoldenrice.InexchangeforcommercialmarketingrightsintheU.S.andotheraffluentmarkets,thecompaniesrecentlyagreedtodonatethetechnologyfreetodevelopingcountries.

8.Still,criticsofagriculturalbiotechnologyerupted.“Aripoff[26]ofthepublictrust,”

grumbledtheRuralAdvancementFoundationInternational,anadvocacygroupbasedinWinnipeg,Canada.Potrykuswasdismayedbysuchnegativereaction.“Itwouldbeirresponsible,”heexclaimed,“nottosayimmoral,nottousebiotechnologytotrytosolvethisproblem!”

Weighing[27]thePerils9.Beneaththehyperbolic[28]talkofFrankenfoods,evenproponentsofagriculturalbiotechnologyagree,liesomerealconcerns.Tobeginwith,allfoods,includingthetrans

genicfoodscreatedthroughgeneticengineering,arepotentialsourcesofallergens.That’sbecausethetransferredgenescontaininstructionsformakingproteinsandsome

proteinsthoseinpeanuts,forexamplecauseallergicreactions.Thenthereistheproblemof“geneticpollution,”[29]asopponentsofbiotechnologytermit.Pollengrainsfromsuchwindpollinated[30]plantsascorn,forinstance,arecarriedfarandwide.Thecontinuingflapover[31]Btcornandcotton.Thegeneofacommonsoilbacteria(Bacillusthuringiensis),anaturalinsecticide,istransferredtotheplantsasprovidedmorefodder[32]forthedebate.Ecologistsareconcernedthatwidespreadplantingofthesecropswillspur[33]Btresistanceamongcroppests,andBtispopularwithorganicfarmers[34].Evenmoreworrisomeareecologicalconcerns.In1999CornellUniversityentomologistJohnLoseyperformedaprovocative,“seatofthepants”[35]laboratoryexperiment.HedustedBtcornpollenonplantspopulatedbymonarchbutterfly[36]caterpillars.Manyofthecaterpillarsdied.LoseyhimselfisnotyetconvincedthatBtcornposesagravedangertoNorthAmerica’smonarchbutterflypopulation,buthedoesthinktheissuedeservesattention.Othersagree.“Theproblemwithtransgenicsistherisksandhazardsinvolved,”saysAshishKothariofKalpavriskh,anIndianenvironmentalgroupworkingtopreservethecountry’sbiodiversity.“Westilldon’tknowwhatthiscandotootherplantsandorganisms.”

10.Therearemorepotentialpitfalls.Amongotherthings,thepossibilityexiststhatastransgenesinpollendrift[37],theywillfertilizewildplants,andweedswillemergethatarehardierandevenmoredifficulttocontrol.Nooneknowshowcommontheexchangeofgenesbetweendomesticplantsandtheirwildrelativesreallyis,butMargaretMellon,directoroftheUnionofConcernedScientists’agricultureandbiotechnologyprogram,isnotaloneinthinkingthatit’shightimewefindout.Saysshe:“Peopleshould

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berespondingtotheseconcernswithexperiments,notassurances[38].”

11.Thatisbeginningtohappen,althoughcontrarytoexpectations.Thereportscominginarenotthatscary.Forthreeyearsnow,UniversityofArizonaentomologistBruceTabashnikhasbeenmonitoringfieldsofBtcottonthatfarmershaveplantedinhisstate.Andinthisinstanceatleast,hesays,“theenvironmentalrisksseemminimal,andthebenefitsseemgreat.”Firstofall,cottonisselfpollinated[39]ratherthanwindpollinated,sothatthespreadoftheBtgeneisoflessconcern.AndbecausetheBtgeneissoeffective,henotes,Arizonafarmersreducedtheiruseofchemicalinsecticides75%.Sofar,thepinkbollworm[40]populationhasnotrebounded[41],indicatingthatthefearedresistancetoBthasnotyetdeveloped.

AssessingthePromise12.Arethecriticsofagriculturalbiotechnologyright?Isbiotech’spromisenothingmorethanoverblown[42]corporatehype[43]?Thepapaya[44]growersinHawaii’sPunadistrictclamortodisagree.In1992anepidemic[45]ofpapayaringspotvirus[46]threatenedtodestroythestate’spapayaindustry;by1994,nearlyhalfthestate’spapayaacreagehadbeeninfected,theirownersforcedtoseekoutsideemployment.Butthenhelparrived,

intheformofavirusresistanttransgenicpapayadevelopedbyCornellUniversityplantpathologistDennisGonsalves.

13.In1995ateamofscientistssetupafieldtrialoftwotransgeniclinesUHSunUPandUHRainbow.Thenontransgenicplantsinthefieldtrialwereastunted[47]messandthetransgenicplantswerehealthy.In1998,afternegotiationswithfourpatentholders,

thepapayagrowersswitchedenmasse[48]tothetransgenicseedsandreclaimedtheirorchards.“Consumeracceptancehasbeengreat,”reportsRustyPerry,whorunsapapayafarmnearPuna.“We’vefoundthatcustomersaremoreconcernedwithhowthefruitslookandtastethanwithwhethertheyaretransgenicornot.”Thewidespreadperceptionthatagriculturalbiotechnologyisintrinsicallyinimical[49]totheenvironmentperplexesGordonConway,theagriculturalecologistwhoheadstheRockefellerFoundation.Heviewsgeneticengineeringasanimportanttoolforachievingwhathehastermeda“doublygreenrevolution.”[50]Ifthetechnologycanmarshal[51]aplant’snaturaldefensesagainstweedsandviruses,ifitcaninducecropstoflourishwithminimalapplicationofchemicalfertilizers,ifitcanmakedrylandagriculturemoreproductivewithoutstraininglocalwatersupplies,thenwhat’swrongwithit?Ofcourse,thesebreakthroughshavenothappenedyet.ButasPotrykusseesit,thereisnoquestionthatagriculturalbiotechnologycanbeharnessedforthegoodofhumankind.Theonlyquestioniswhetherthereisthecollectivework.

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 Notes

[1]husk[hQsk]n.(果类或谷物的)外壳

(通常用复数),皮,无价值之物vt.剥

……的壳,削

[2]behold[bi5h[uld]vt.把……视为vi.看

[3]courtesy[5k[:tisi]n.谦恭,允许,礼

[4]carotene[5kAr[ti:n]n.[生 化]胡 萝

卜素

[5]goldenricen.金稻米

[6]finicky[5finiki]adj.过分注意的,过

分讲究的,过分周到的

[7]greenhouse[5gri:nhaUs]n.温室

[8]opponent[[5p[un[nt]n.反对者

[9]Frankenfood[5frAnkenfu:d]n.基因

工程食品

[10]entangle[in5tANgl]vt.使 缠 上,纠

缠,卷入,连累,使混乱

[11]politicalbaggagen.政治包袱

[12]ironclad[ai[n5klAd]adj.装甲的,打

不破的

[13]polarize[5p[Jl[raiz]v.(使)偏 振,(使)极化,(使)两极分化

[14]scrutiny[5skru:tini]n.详细审查

[15]curb[k[:b]n.抑制

[16]acrimonious[7Akri5m[unj[s]adj.严

厉的,辛辣的

[17]debut[5debjU:]n.v.初 次 登 场,开

[18]environmentalist[in9vai[r[n5mentlist]

n.环保论者

[19]consumeradvocacygroup消费者觉悟

团体

[20]monoculture [5mRn[UkQltF[]n.[农]单一栽培,单作

[21]compelling [k[m5peliN]adj.强 制

的,强迫的,引人注目的

[22]wellfedfolk吃饱了的国民

[23]jetv.乘喷气机

[24]fullprofessorn.正教授

[25]empathy[5emp[Wi]n.移 情 作 用,[心]神入

[26]ripoffn.偷窃

[27]weighvt.称……重量,称,掂量vi.重

(若干)[28]hyperbolic[7haip[:5bClik]adj.双曲

线的,夸张的

[29]geneticpollutionn.遗传污染

[30]windpollinated[5pRlineit]adj.风媒

传粉的

[31]flapovern.争议不决

[32]foddern.饲料,草料,(创作的)素材,

弹药

[33]spur[sp[:]v.鞭策,刺激,疾驰,驱

[34]organicfarmer有机农民

[35]seatofthepantsadj.经验性的,基于

直觉和经验而不是推理的

[36]monarchbutterfly帝王蝶

[37]pollendrift花粉飘逸

[38]assurance[[5Fu[r[ns]n.断言

[39]selfpollinatedadj.自花授粉的

[40]bollworm[5b[Jlw…m]n.一 种 蛾 的

幼虫,螟蛉

[41]rebound[ri5baund]n.回弹v.回弹

[42]overblown[[uv[5bl[un]adj.停 息

的,盛开过的

[43]hype[haip]n.(美 俚)皮 下 注 射,骗

局,大肆宣传,大做广告,瘾君子

[44]papaya[p[5pai[]n.番 木 瓜 树,番 木

瓜果

[45]epidemic[7epi5demik]adj.流 行 的,

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133  

传染的,流 行 性n.时 疫,疫 疾 流 行,(风尚等的)流行,流行病

[46]ringspot[riNspRt]virusn.环斑病毒

[47]stunted[5sQntid]adj.成 长 受 妨 碍

的,矮小的

[48]enmasse [enmAs]adv.全 体 地,一

同地

[49]inimical[i5nimikl]adj.敌意的,有害

[50]doublygreenrevolutionn.双 重 绿 色

革命

[51]marshal[5mB:F[l]n.元帅,典礼官,执行官,司仪官vt.整顿,配置,汇集

vi.排列,集合

犈狊狊犪狔49 犘狉狅狋犲狅犿犻犮狊

1.Proteomics[1]isthelargescalestudyofproteins,particularlytheirstructuresandfunctions.Thistermwascoinedtomakeananalogy[2]withgenomics,andisoftenviewedasthe“nextstep”,butproteomicsismuchmorecomplicatedthangenomics.Mostim

portantly,whilethegenomeisaratherconstantentity[3],theproteomeisconstantlychangingthroughitsbiochemicalinteractionswiththegenomeandtheenvironment.Oneorganismwillhaveradically[4]differentproteinexpressionindifferentpartsofitsbody,indifferentstagesofitslifecycleandindifferentenvironmentalconditions.

2.Theentiretyofproteinsinexistenceinanorganismthroughoutitslifecycle,oronasmallerscaletheentiretyofproteinsfoundinaparticularcelltypeunderaparticulartypeofstimulation,arereferredtoastheproteomeoftheorganismorcelltyperespectively.

3.Withcompletionofaroughdraftofthehumangenome,manyresearchersarenowlookingathowgenesandproteinsinteracttoformotherproteins.AsurprisingfindingoftheHumanGenomeProjectisthattherearefarfewergenesthatcodeforproteinsinthehumangenomethanthereareproteinsinthehumanproteome(~22,000genesvs~200000proteins).Thelargeincreaseinproteindiversityisthoughttobeduetoalternativesplicing[5]andposttranslationalmodificationofproteins[6].

4.Tocatalogue[7]allhumanproteinsandascertain[8]theirfunctionsandinteractionspresentsadauntingchallengeforscientists.Aninternationalcollaborationtoachievethese

goalsisbeingcoordinatedbytheHumanProteomeOrganization.

Branchesofproteomics5.Proteinseparation.Basictoallproteomictechnologiesareproteinseparation,theseparationofacomplexmixturesothatindividualproteinsaremoreeasilyprocessedwithothertechniques.

6.Proteinidentification.Wellknownmethodsincludethelowthroughput[9]sequencingthroughEdmandegradation[10].Moretruehighthroughputproteomictechniquesarebasedonmassspectrometry[11],commonlypeptidemassfingerprinting[12]onsimplerin

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struments,ordenovo[13]sequencingoninstrumentscapableofmorethanoneroundofmassspectrometry.Antibodybasedassayscanalsobeused,butareuniquetooneprotein.

7.Proteinquantification.Gelbasedmethodsareused,includingdifferentialstainingofgelswithfluorescentdyes[14](differencegelelectrophoresis).Gelfreemethodsincludevarioustaggingorchemicalmodificationmethods,suchasisotopecodedaffinitytags(ICATs)[15]orcombinedfractionaldiagnoalchromatography(COFRADIC)[16].

8.Proteinsequenceanalysis.Thisismoreofabioinformaticbranch,dedicatedtosearchingdatabasesforpossibleproteinorpeptidematches,butalsofunctionalassignmentofdomains[17],predictionoffunctionfromsequence,andevolutionaryrelationshipsofproteins.

9.Structuralproteomics.Thisconcernsthehighthroughputdeterminationofproteinstructuresinthreedimensionalspace.Commonmethodsarexraycrystallography[18]

andNMRspectroscopy[19].10.Interactionproteomics.Thisconcernstheinvestigationofproteininteractionsontheatomic,molecularandcellularlevels

11.Proteinmodification.Almostallproteinsaremodifiedfromtheirpuretranslatedaminoacidsequence,socalledposttranslationalmodification[20].Specializedmethodshavebeendevelopedtostudyphosporylation(phosphoproteomics[21])andglycosylation(glycoproteomics[22]).

Keytechnologiesusedinproteomics12.Oneandtwodimensionalgelelectrophoresisareusedtoidentifytherelativemassofa

proteinanditsisoelectricpoint[23].13.Xraycrystallographyandnuclearmagneticresonanceareusedtocharacterizethethree

dimensionalstructureofpeptidesandproteins.14.Tandemmassspectrometry[24]combinedwithreversephasechromatography[25]or2Delectrophoresis[26]isusedtoidentifyandquantifyallthelevelsofproteinsfoundincells.

15.Affinitychromatography[27],yeasttwohybridtechniques[28],fluorescenceresonanceenergytransfer(FRET)[29],andSurfacePlasmonResonance[30](SPR)areusedtoidentifyproteinproteinandproteinDNAbindingreactions.

ProteindatabasesPIR,SwissProt,Pfam,ProteinDataBank

 Notes

[1]proteomics[pr[uti5[umiks]n.蛋 白

组学

[2]analogy[[5nAl[dVi]n.类似,类推

[3]entity[5entiti]n.实体

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[4]radically[5rAdik[li]adv.根本上,以

激进的方式

[5]alternativesplicing[5splaisiN]n.选

择性剪切

[6]posttranslationalmodificationofprotein翻译后蛋白质修饰

[7]catalogue[5kAt[lCg]vt.编制目录

[8]ascertain[7AsE5tein]vt.确定,探知

[9]lowthroughputadj.低通量的

[10]Edmandegradationn.艾德曼降解法

[11]massspectrometry[spek5trRmitri]n.质谱

[12]peptidemassfingerprinting肽 质 量 指

纹图谱

[13]denovo[di:n[Uv[u]adj.从头的

[14]fluorescent[flU[5res[nt]dyen.荧光

染料

[15]isotopecodedaffinitytags(ICATs)[5ais[ut[up5k[Udid[5finititAgs]同

位素被编码的亲和力标记

[16]combinedfractionaldiagnoalchromatography[7kr[Um[5tRgr[fi](COFRADIC)联 合 分 数 对 角 色 谱 法。用

分选标记 肽 段 来 达 到 鉴 定 的 目 的。用

于蛋白质后翻译后修饰分析,已经被应

用于 甲 硫 氨 酸肽 段、半 胱 氨 酸肽 段、蛋白质 N末 端 肽 段、18O标 记 的 C末

端分选。[17]functionalassignmentofdomainn.结

构域功能指派

[18]xraycrystallography[krist[5lRgr[fi]

n.X射线晶体学

[19]NMRspectroscopyn.核 磁 共 振(NuclearMagneticResonance)谱

[20]posttranslationalmodificationn.翻译

后修饰

[21]phosphoproteomics [fRsf[pr[uti5[umiks]n.磷酸蛋白组学

[22]glycoproteomics [glaik[Upr[uti5[umiks]n.糖蛋白组学

[23]isoelectric point [7ais[Ui5lektrikpRint]n.等电点

[24]Tandemmassspectrometryn.串联质

[25]reversephasechromatographyn.反相

层析

[26]2Delectrophoresis[i9lektr[f[5ri:sis]

n.双向电泳

[27]affinitychromatographyn.亲和层析

[28]yeasttwohybridtechniquen.酵母双

杂交技术

[29]fluorescenceresonanceenergytransfer(FRET)n.荧光共振能量转移

[30]SurfacePlasmon[5plAz7m[n]Resonance(SPR)表 面 等 离 谐 振。一 种 基

于物理光学原理的新型生化分析系统,

SPR技术作为一种表在反应 的 生 物 传

感技术,具 有 很 重 要 的 生 化 分 析 能 力,可用于无 标 记 实 时 监 测 许 多 种 类 生 物

分子之间的反应。

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犝犖犐犜14 犅犐犗犐犖犉犗犚犕犃犜犐犆犛

犈狊狊犪狔50 犅犻狅犻狀犳狅狉犿犪狋犻犮狊,狋犺犲犅犪狊犻犮狊

1.Bioinformatics[1]andcomputationalbiology[2]involvetheuseoftechniquesincludingap

pliedmathematics,informatics[3],statistics,computerscience,artificialintelligence,

chemistryandbiochemistrytosolvebiologicalproblemsusuallyonthemolecularlevel.Researchincomputationalbiologyoftenoverlapswithsystembiology[4].Majorresearcheffortsinthefieldincludesequencealignment[5],genefinding[6],genomeassembly[7],proteinstructurealignment[8],proteinstructureprediction,predictionofgeneexpressionandproteinproteininteractions,andthemodelingofevolution[9].

2.Thetermsbioinformaticsandcomputationalbiologyareoftenusedinterchangeably.Howeverbioinformaticsmoreproperlyreferstothecreationandadvancementofalgorithms[10],computationalandstatisticaltechniques,andtheorytosolveformaland

practicalproblemsposedbyorinspiredfromthemanagementandanalysisofbiologicaldata.Computationalbiology,ontheotherhand,referstohypothesisdriveninvestigationofaspecificbiologicalproblemusingcomputers,carriedoutwithexperimentalandsimulateddata,withtheprimarygoalofdiscoveryandtheadvancementofbiologicalknowledge.AsimilardistinctionismadebyNationalInstitutesofHealthintheirworkingdefinitions[11]ofBioinformaticsandComputationalBiology,whereitisfurtherem

phasizedthatthereisatightcouplingofdevelopmentsandknowledgebetweenthemorehypothesisdrivenresearchincomputationalbiologyandtechniquedrivenresearchinbioinformatics.Computationalbiologyalsoincludeslesserknownbutequallyimportantsubdisciplines[12]suchascomputationalbiochemistryandcomputationalbiophysics.

3.Acommonthreadinprojectsinbioinformaticsandcomputationalbiologyistheuseofmathematicaltoolstoextractusefulinformationfromdataproducedbyhighthroughputbiologicaltechniquessuchasgenomesequencing.Arepresentativeprobleminbioinformaticsistheassemblyofhighqualitygenomesequencesfromfragmentary“shotgun”

DNAsequencing[13].Othercommonproblemsincludethestudyofgeneregulationusingdatafrommicroarrays[14]ormassspectrometry.

MajorResearchAreasofBioinformaticsSequenceanalysis4.SincethePhageΦX174wassequencedin1977,theDNAsequencesofhundredsofor

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ganismshavebeendecodedandstoredindatabases.Thesedataareanalyzedtodeterminegenesthatcodeforproteins,aswellasregulatorysequences.Acomparisonof

geneswithinaspeciesorbetweendifferentspeciescanshowsimilaritiesbetweenproteinfunctions,orrelationsbetweenspecies(theuseofmolecularsystematicstoconstruct

phylogenetictrees).Withthegrowingamountofdata,itlongagobecameimpracticaltoanalyzeDNAsequencesmanually.Today,computerprogramsareusedtosearchthe

genomeofthousandsoforganisms,containingbillionsofnucleotides.Theseprogramscancompensateformutations(exchanged,deletedorinsertedbases)intheDNAse

quence,inordertoidentifysequencesthatarerelated,butnotidentical.Avariantofthissequencealignmentisusedinthesequencingprocessitself.Thesocalledshotgunsequencingtechnique(whichwasused,forexample,byTheInstituteforGenomicResearchtosequencethefirstbacterialgenome,Haemophilusinfluenza)doesnotgiveasequentiallistofnucleotides,butinsteadthesequencesofthousandsofsmallDNAfragments(eachabout600~800nucleotideslong).Theendsofthesefragmentsoverlapand,whenalignedintherightway,makeupthecompletegenome.Shotgunse

quencingyieldssequencedataquickly,butthetaskofassemblingthefragmentscanbe

quitecomplicatedforlargergenomes.InthecaseoftheHumanGenomeProject,ittookseveralmonthsofCPUtime[15]toassemblethefragments.Shotgunsequencingisthemethodofchoiceforvirtuallyallgenomessequencedtoday,andgenomeassemblyalgorithmsareacriticalareaofbioinformaticsresearch.

5.Anotheraspectofbioinformaticsinsequenceanalysisistheautomaticsearchforgenesandregulatorysequenceswithinagenome.Notallofthenucleotideswithinagenomearegenes.Withinthegenomeofhigherorganisms,largepartsoftheDNAdonotserveanyobviouspurpose.ThissocalledjunkDNA[16]may,however,containunrecognizedfunctionalelements.Bioinformaticshelpstobridgethegapbetweengenomeandproteomeprojects—forexample,intheuseofDNAsequencesforproteinidentification.

Genomeannotation[17]

6.Inthecontextofgenomics,annotationistheprocessofmarkingthegenesandotherbiologicalfeaturesinaDNAsequence.Thefirstgenomeannotationsoftwaresystemwasdesignedin1995byOwenWhite,whowaspartoftheteamthatsequencedandanalyzedthefirstgenomeofafreelivingorganismtobedecoded,thebacteriumHaemophilusinfluenzae.Dr.Whitebuiltasoftwaresystemtofindthegenes(placesintheDNAse

quencethatencodeaprotein),thetransferRNA,andotherfeatures,andtomakeinitialassignmentsoffunctiontothosegenes.Mostcurrentgenomeannotationsystemsworksimilarly,buttheprogramsavailableforanalysisofgenomicDNAareconstantlychangingandimproving.

Computationalevolutionarybiology7.Evolutionarybiologyisthestudyoftheoriginanddescentofspecies,aswellastheir

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changeovertime.Informaticshasassistedevolutionarybiologistsinseveralkeyways;

ithasenabledresearcherstotracetheevolutionofalargenumberoforganismsbymeasuringchangesintheirDNA,ratherthanthroughphysicaltaxonomy[18]orphysiologicalobservationsalone,morerecently,compareentiregenomes,whichpermitsthestudyofmorecomplexevolutionaryevents,suchasgeneduplication[19],lateralgenetransfer[20],andthepredictionofbacterialspeciation[21]factors,buildcomplexcomputationalmodelsofpopulationstopredicttheoutcomeofthesystemovertimetrackandshareinformationonanincreasinglylargenumberofspeciesandorganisms

Futureworkendeavourstoreconstructthenowmorecomplextreeoflife[22]

8.Theareaofresearchwithincomputersciencethatusesgeneticalgorithms[23]issometimesconfusedwithcomputationalevolutionarybiology,butthetwoareasareunrelated.

Measuringbiodiversity9.Biodiversityofanecosystemmightbedefinedasthetotalgenomiccomplementofaparticularenvironment,fromallofthespeciespresent,whetheritisabiofilm[24]inanabandonedmine,adropofseawater,ascoopofsoil,ortheentirebiosphereoftheplanetEarth.Databasesareusedtocollectthespeciesnames,descriptions,distributions,

geneticinformation,statusandsizeofpopulations,habitatneeds,andhoweachorganisminteractswithotherspecies.Specializedsoftwareprogramsareusedtofind,visualize,andanalyzetheinformation,andmostimportantly,communicateittootherpeo

ple.Computersimulatesmodelsuchthingsaspopulationdynamics,orcalculatethecumulativegenetichealthofabreedingpool[25](inagriculture)orendangeredpopulation(inconservation).OneveryexcitingpotentialofthisfieldisthatentireDNAse

quences,orgenomesofendangeredspeciescanbepreserved,allowingtheresultsofNature’sgeneticexperimenttoberememberedinsilico[26],andpossiblyreusedinthefuture,evenifthatspeciesiseventuallylost.

Analysisofgeneexpression10.TheexpressionofmanygenescanbedeterminedbymeasuringmRNAlevelswithmulti

pletechniquesincludingmicroarrays,expressedcDNAsequencetag(EST)[27]sequencing,serialanalysisofgeneexpression(SAGE)[28]tagsequencing,massivelyparallelsignaturesequencing(MPSS)[29],orvariousapplicationsofmultiplexedinsituhybridization[30].Allofthesetechniquesareextremelynoiseprone[31]and/orsubjecttobiasinthebiologicalmeasurement,andamajorresearchareaincomputationalbiologyinvolvesdevelopingstatisticaltoolstoseparatesignalfromnoiseinhighthroughputgeneexpressionstudies.Suchstudiesareoftenusedtodeterminethegenesimplicatedinadisorder:onemightcomparemicroarraydatafromcancerousepithelialcellstodatafromnoncancerouscellstodeterminethetranscriptsthatareupregulated[32]anddownregu

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lated[33]inaparticularpopulationofcancercells.

Analysisofregulation11.Regulationisthecomplexorchestration[34]ofeventsstartingwithanextracellularsig

nalandultimatelyleadingtoanincreaseordecreaseintheactivityofoneormoreproteinmolecules.Bioinformaticstechniqueshavebeenappliedtoexplorevariousstepsinthisprocess.Forexample,promoteranalysis[35]involvestheelucidationandstudyofsequencemotifs[36]inthegenomicregionsurroundingthecodingregionofagene.ThesemotifsinfluencetheextenttowhichthatregionistranscribedintomRNA.Expressiondatacanbeusedtoinfergeneregulation:onemightcomparemicroarraydatafromawidevarietyofstatesofanorganismtoformhypothesesaboutthegenesinvolvedineachstate.Inasinglecellorganism,onemightcomparestagesofthecellcycle,alongwithvariousstressconditions(heatshock[37],starvation,etc.).Onecanthenapplyclusteringalgorithms[38]tothatexpressiondatatodeterminewhichgenesarecoex

pressed[39].Forexample,theupstreamregions(promoters)ofcoexpressedgenescanbesearchedforoverrepresented[40]regulatoryelements.

Analysisofproteinexpression12.Proteinmicroarraysandhighthroughput(HT)massspectrometry(MS)canprovideasnapshotoftheproteinspresentinabiologicalsample.BioinformaticsisverymuchinvolvedinmakingsenseofproteinmicroarrayandHT MSdata;theformerapproachfacessimilarproblemsaswithmicroarraystargetedatmRNA,thelatterinvolvesthe

problemofmatchinglargeamountsofmassdataagainstpredictedmassesfromproteinsequencedatabases,andthecomplicatedstatisticalanalysisofsampleswheremultiple,

butincompletepeptidesfromeachproteinaredetected.

Analysisofmutationsincancer13.Massivesequencingeffortsarecurrentlyunderwaytoidentifypointmutations[41]inavarietyofgenesincancer.Thesheervolumeofdataproducedrequiresautomatedsystemstoreadsequencedata,andtocomparethesequencingresultstotheknownsequenceofthehumangenome,includingknowngermlinepolymorphisms[42].

14.Oligonucleotidemicroarrays,includingcomparativegenomichybridizationandsinglenucleotidepolymorphism[43]arrays,abletoprobesimultaneouslyuptoseveralhundredthousandsitesthroughoutthegenomearebeingusedtoidentifychromosomalgainsandlossesincancer.HiddenMarkovmodel[44]andchangepointanalysismethodsarebeingdevelopedtoinferrealcopynumberchangesfromoftennoisydata.Furtherinformaticsapproachesarebeingdevelopedtounderstandtheimplicationsoflesions[45]foundtoberecurrent[46]acrossmanytumors.

15.Somemoderntools(e.g.,Quantum3.1)providetoolforchangingtheproteinsequenceatspecificsitesthroughalterationstoitsaminoacidsandpredictchangesinthe

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bioactivityaftermutations.

Predictionofproteinstructure16.Proteinstructurepredictionisanotherimportantapplicationofbioinformatics.Theami

noacidsequenceofaprotein,thesocalledprimarystructure[47],canbeeasilydeterminedfromthesequenceonthegenethatcodesforit.Inthevastmajorityofcases,this

primarystructureuniquelydeterminesastructureinitsnativeenvironment.(Ofcourse,thereareexceptions,suchasthebovinespongiformencephalopathy[48]—aka[49]

MadCowDisease[50]—prion).Knowledgeofthisstructureisvitalinunderstandingthefunctionoftheprotein.Forlackofbetterterms,structuralinformationisusuallyclassifiedasoneofsecondary,tertiaryandquaternarystructure[51].Aviablegeneralsolutiontosuchpredictionsremainsanopenproblem.Asofnow,mosteffortshavebeendirectedtowardsheuristics[52]thatworkmostofthetime.

17.Oneofthekeyideasinbioinformaticsisthenotionofhomology[53].Inthegenomicbranchofbioinformatics,homologyisusedtopredictthefunctionofagene:ifthese

quenceofgeneA,whosefunctionisknown,ishomologoustothesequenceofgeneB,

whosefunctionisunknown,onecouldinferthatBmayshareA’sfunction.Inthestructuralbranchofbioinformatics,homologyisusedtodeterminewhichpartsofaproteinareimportantinstructureformationandinteractionwithotherproteins.Inatechniquecalledhomologymodelling[54],thisinformationisusedtopredictthestructureofaproteinoncethestructureofahomologousproteinisknown.Thiscurrentlyremainstheonlywaytopredictproteinstructuresreliably.

18.Oneexampleofthisisthesimilarproteinhomologybetweenhemoglobininhumansandthehemoglobininlegumes(leghemoglobin[55]).Bothservethesamepurposeoftrans

portingoxygenintheorganism.Thoughbothoftheseproteinshavecompletelydifferentaminoacidsequences,theirproteinstructuresarevirtuallyidentical,whichreflectstheirnearidenticalpurposes.

19.Othertechniquesforpredictingproteinstructureincludeproteinthreading[56]anddenovophysicsbasedmodeling.

Comparativegenomics20.Thecoreofcomparativegenomeanalysisistheestablishmentofthecorrespondencebetweengenes(orthologyanalysis[57])orothergenomicfeaturesindifferentorganisms.Itistheseintergenomic[58]mapsthatmakeitpossibletotracetheevolutionaryprocessesresponsibleforthedivergence[59]oftwogenomes.A multitudeofevolutionaryeventsactingatvariousorganizationallevelsshapesgenomeevolution.Atthelowestlevel,

pointmutationsaffectindividualnucleotides.Atahigherlevel,largechromosomalsegmentsundergoduplication,lateraltransfer,inversion[60],transposition,deletionandinsertion.Ultimately,wholegenomesareinvolvedinprocessesofhybridization,

polyploidization[61]andendosymbiosis[62],oftenleadingtorapidspeciation[63].Thecom

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plexityofgenomeevolutionposesmanyexcitingchallengestodevelopersofmathematicalmodelsandalgorithms,whohaverecoursetoaspectraofalgorithmic,statisticalandmathematicaltechniques,rangingfromexact,heuristics,fixedparameterandapproximationalgorithmsforproblemsbasedonparsimony[64]modelstoMarkovChainMonteCarloalgorithmsforBayesiananalysisofproblemsbasedonprobabilisticmodels[65].Manyofthesestudiesarebasedonthehomologydetectionandproteinfamilycomputation.

Modelingbiologicalsystems21.Systemsbiologyinvolvestheuseofcomputersimulationsofcellularsubsystems[66](suchasthenetworksofmetabolitesandenzymeswhichcomprisemetabolism,signaltransductionpathways[67]andgeneregulatorynetworks)tobothanalyzeandvisualizethecomplexconnectionsofthesecellularprocesses.Artificiallifeorvirtualevolution[68]attemptstounderstandevolutionaryprocessesviathecomputersimulationofsimple(artificial)lifeforms.

Highthroughputimageanalysis22.Computationaltechnologiesareusedtoaccelerateorfullyautomatetheprocessing,

quantificationandanalysisoflargeamountsofhighinformationcontentbiomedicalimagery.Modernimageanalysissystemsaugmentanobserver’sabilitytomakemeasurementsfromalargeorcomplexsetofimages,byimprovingaccuracy,objectivity[69],orspeed.Afullydevelopedanalysissystem maycompletelyreplacetheobserver.Althoughthesesystemsarenotuniquetobiomedicalimagery,biomedicalimagingisbecomingmoreimportantforbothdiagnostics[70]andresearch.Someexamplesare:highthroughputandhighfidelityquantificationandsubcellularlocalization(highcontentscreening,cytohistopathology[71]),morphometrics[72],clinicalimageanalysisandvisualization,determiningtherealtime[73]airflowpatternsinbreathinglungsoflivinganimals,quantifyingocclusion[74]sizeinrealtimeimageryfromthedevelopmentofandrecoveryduringarterialinjury,makingbehaviouralobservationsfromextendedvideorecordingsoflaboratoryanimals,infraredmeasurementsformetabolicactivitydetermination.

Softwaretools23.Firstgenerationbioinformaticstoolsconsistedofapplications,usuallywithatextbasedinterface,whichperformedaspecifictaskwell.ThecomputationalbiologytoolbestknownamongbiologistsisprobablyBLAST[75],analgorithmforsearchinglargedatabasesofproteinorDNAsequences.TheNCBI[76]providesapopularwebbasedimplementationthatsearchestheirmassivesequencedatabases.Alsofairlyearlyon,duetotheamassingofsequenceandannotationdata,keywordsearchengineswhichwereabletoresolvegeneandproteinsynonymswereimportant.Intheseearlydays,computer

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scripting[77]languagessuchasPerlandPythonwereoftenusedtointerfacewithbiologicaldatabasesandparse[78]outputfrombioinformaticsprogramswritteninlanguagessuchasCorC++,andmuchlegacycode[79]isstillinusetoday.Today,manyotherlanguagesareusedtoauthor[80]excellentsoftware,andcommunitiesofbioinformaticsprogrammershavesetupfreeopensourcebioinformaticsprojectstodevelopanddistributethetoolsandmodules[81]theyproduce.

24.Asthedatasourcesexpandedanddiversified,bothincontentandgeography,bioinformaticmetasearchengines[82],suchasSequenceprofilingtools[83],emergedtohelpfindrelevantinformationfromseveraldatabases.Thesemetasearchenginesmightindexdatafromalocalserverorevenfromapanelofthirdpartyservices.

25.Morerecently,SOAP[84]basedinterfaceshavebeendevelopedforawidevarietyofbioinformaticsapplicationsallowinganapplicationrunningononecomputerinonepartoftheworldtousealgorithms,dataandcomputingresourcesonserversinotherpartsoftheworld.AlargeavailabilityoftheseSOAPbasedbioinformaticswebservices,alongwiththeopensourcebioinformaticscollections,leadtothenextgenerationofbioinformaticstools:theintegratedbioinformaticsplatform.Thesetoolsrangefromacollectionofstandalonetoolswithacommondataformatunderasingle,slickstandaloneorwebbasedinterface,tointegrative[85]andextensible[86]bioinformaticsworkflowdevelopmentenvironments.

26.AninterestingnoveldirectionforbioinformaticsapplicationsisillustratedbyQPharm’

sQuantum3.1,anexampleofthebioinformaticspostQSAR[87]technologyapplyingquantumandmolecularphysicsinsteadofstatisticalmethods.

 Notes

[1]bioinformaticsn.生物信息学

[2]computational[7kRmpjU:5teiF[n[l]

biology计算生物学

[3]informatics[7inf[5mAtiks]n.信息学

[4]systembiologyn.系统生物学

[5]sequencealignment[[5lainm[nt]n.序列比对

[6]genefindingn.基因识别

[7]genomeassemblyn.基因组(序列)装

[8]proteinstructurealignmentn.蛋白质

结构比对

[9]modelingofevolutionn.进化建模

[10]algorithm [5Alg[riT[m]n.运 算 法

则,算法

[11]workingdefinitionn.使用定义

[12]subdiscipline[5sQb5disipliN]n.分支

学科

[13]shotgun[5FQtgQn]DNAsequencingn.鸟枪法DNA测序

[14]microarrayn.微阵列

[15]CPUtimen.中 央 处 理 器 时 间(centralprocessingunittime)

[16]junkDNAn.垃圾DNA[17]genomeannotation [9An[J5teiFLn]

n.基因组注释

[18]physicaltaxonomyn.自然分类法

[19]geneduplication[7djU:pli5keiF[n]n.

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基因重复

[20]lateralgenetransfer侧向基因转移

[21]speciation[7spi:Fi5eiF[n]n.物种形

[22]treeoflife生命之树(进化树)[23]geneticalgorithms遗传算法

[24]biofilm[5bai[film]n.细菌生物被膜,

又称菌膜(bacterialbiofilm),是单一或

多种细菌在不利于其生长的环境下,产生藻酸盐多糖使细菌相 互 粘 连 形 成 膜

状物附于病灶 的 表 面 或 导 管 内。这 是

细菌为适应环境维持自 身 生 命 所 发 生

的形态学的变化,从而增强了细菌对外

环境的抵抗力。这 也 成 为 一 些 细 菌 对

抗生素产生广 泛 耐 药 的 重 要 原 因。临

床上许多顽固性,难治性感染可能均与

形成细菌生物被膜有关。[25]breedingpooln.繁殖种群

[26]insilico[insilik[u]adv.在芯片上

[27]expressedcDNAsequencetag(EST)

n.表达cDNA序列标签

[28]serialanalysisofgeneexpression(SAGE)n.基因表达连续分析

[29]massivelyparallelsignaturesequencing(MPSS)n.大规模平行指纹测序

[30]multiplexedinsitu[in5saitju:]hybridizationn.多元原位杂交

[31]noiseproneadj.易产生噪音的

[32]upregulatedadj.上调的(活性增高)[33]downregulatedadj.下 调 的(活 性 降

低)[34]orchestration[C:kis5treiFn]n.和 谐

的结合,管弦乐作曲法

[35]promoteranalysisn.启动子分析

[36]sequencemotifsn.序列模序

[37]heatshockn.热休克,热激

[38]clusteringalgorithmsn.聚 类 分 析 运

算法则

[39]coexpressv.共表达

[40]overrepresentedadj.超过比例的

[41]pointmutationsn.点突变

[42]germlinepolymorphismsn.种 质 资 源

多态性

[43]singlenucleotidepolymorphismn.单

核苷酸多态性

[44]HiddenMarkovModel(HMM)n.隐

马尔可夫模型

[45]lesion[5li:V[n]n.损伤

[46]recurrent[ri5kQr[nt]adj.再发生的,

周期性发生的,循环的

[47]primarystructuren.一级结构

[48]bovinespongiformencephalopathyn.牛绵状脑

[49]aka亦称(alsoknownas的缩写)[50]MadCowDiseasen.疯牛病

[51]secondary,tertiary,quaternarystructuren.二、三、四级结构

[52]heuristics[hju[5ristiks]n.启发式 方

[53]homology[hC5mCl[dVi]n.同源性

[54]homologymodellingn.同 源 建 模,即

利用实验确定的蛋白质 结 构 为 模 板 来

预测另一种具有相似氨 基 酸 序 列 的 蛋

白质(靶)的构象。[55]leghemoglobin[7leghi:m[5gl[Ubin]

n.豆血红蛋白

[56]proteinthreading蛋白质穿针引线法

[57]orthology[5R:WCl[dVi]analysisn.直系同源分析

[58]intergenomic [in5t[:dVi5n[umik]

adj.基因组间的

[69]divergence[dai5v…dV[ns]n.趋异进

[60]inversion[in5v[:F[n]n.(遗传)倒位

[61]polyploidization [pRli9plRidai5zeiF[n]n.(遗传)多倍体化

[62]endosymbiosis[5end[J9simbai5[Jsis]

n.内共生

[63]rapidspeciationn.快速物种形成

[64]parsimony[5pB:sim[ni]modelsn.简

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约模型

[65]probabilistic[7prRb[bi5listik]modelsn.概率模型

[66]cellularsubsystemsn.细胞亚系统

[67]signaltransductionpathwaysn.信 号

转导模型

[68]virtualevolution虚拟进化

[69]objectivity[9RbdVek5tiviti]n.客 观

[70]diagnostics[7dai[g5nCstiks]n.诊 断

[71]cytohistopathology [7sait[u7hist[Up[5WC:l[dVi]n.细胞组织病理学

[72]morphometrics[9mC:f[J5metriks]n.[用作单或复](尤指生物体的)形态测

定,形态特征

[73]realtimeadj.实时的

[74]occlusion[[5klU:V[n]n.梗塞,通道

或脉管的阻塞或闭合

[75]BLASTn.局 部 相 似 性 基 本 查 询 工 具

(BasicLocalAlignmentSearchTool)[76]NCBIn.美国国家生物技术信息 中 心

(网站)(NationalCenterForBiotechnolgyInformation)

[77]computerscriptinglanguagesn.计 算

机脚本语言

[78]parse[pB:z]vt.解析

[79]legacycode[5leg[sik[ud]n.遗产代

[80]authorvt.创造,写作

[81]module[5mCdju:l]n.模块

[82]metasearchenginesn.多元搜索引擎

(是在前述搜索引擎基础上建立的可以

同时查 询 多 个 搜 索 引 擎 的 WWW 站

点)[83]Sequenceprofilingtoolsn.序 列 作 图

工具

[84]SOAPn.符号最优汇编程序(SymbolicOptimal[Optimum]AssemblyProgram)

[85]integrative[5intigreitiv]adj.综 合

的,一体化的

[86]extensible[ik5stensibl]adj.可 展 开

的,可扩张的,可延长的

[87]QSARn.(一 种 使 用 广 泛 的 药 物 设 计

方 法)定 量 构 效 方 法 (quantitativestructureactivityrelationship)

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附录1 生物专业英语常见词素

一、表示数量的词素

1.haplo,mono,uni单,一,独 :haploid单倍体 monoxide一氧化物 monoatomic单原子的

2.bi,di,dipl,twi,du二,双,两,偶:bicolor双色dichromatic双色的diplobacillus双杆

菌dikaryon双核体twin孪生dual双重的

3.tri三,丙:triangle三角triacylglycerol三酰甘油tricarboxylicacidcycle三羧酸循环

4.quadri,quadru,quart,tetr,tetra四:quadrilateral四边的quadrivalent四价的quadru

ped四足动物tetrode四极管tetracycline四环素

5.pent,penta,quique五:pentose戊 糖pentagon五 角 形pentane戊 烷quintuple五 倍 的

pentamer五聚体

6.hex,hexa,sex六:hexose己糖hexapod六足动物hexapoda昆虫纲hexamer六聚体

7.hepta,sept(i)七:heptane庚烷heptose庚糖heptoglobin七珠蛋白

8.oct八:octpus章鱼octagon八角形octane辛烷octose辛糖

9.enne,nona九:nonapeptide九肽enneahedron九面体

10.deca,deka十:decapod十足目动物decahedron十面体decagram 十克

11.hecto百:hectometer百米hectoliter百升hectowatt百瓦

12.kilo千:kilodalton(kD)千道尔顿kilobase千碱基kiloelectronvolt千电子伏特

13.deci十分之一,分:decimeter分米decigram十分之一克

14.centi百分之一:centimeter厘米centimorgan厘摩

15.milli千分之一,毫:millimole毫摩尔 milliliter毫升

16.micro百万分之一,微,微小,微量:microgram微克 microorganism 微生物 microecology微生态学 micropipette微量移液器

17.nano十亿分之一,毫微,纳:nanosecond十亿分之一秒nanometer纳米

18.demi,hemi,semi半:demibarrel半桶hemicerebrum大脑半球semiopaque半透明semi

allele半等位基因semiconductor半导体

19.holo全,整体,完全:holoenzyme全酶holoprotein全蛋白holocrine全(浆分)泌的

20.mega巨大,兆,百万:megaspore大孢子,megabase兆碱基megakaryocyte巨核细胞meg

avolt兆伏 megalopolitan特大城市

21.macro大,巨大,多:macrophage巨噬细胞 macrogamete大配子 macroelement大量元 素

macromolecular大分子的

22.poly,multi,mult多,复合:polyacrylate聚丙烯酸酯polymerase聚合酶 multichain多链

的multinucleate多核的 multicistronicmRNA多顺反子mRNAmulticopy多拷贝

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附录1 生物专业英语常见词素

146  

二、表示颜色的词素

1.chrom颜色

chromophore生色团chromosome染色体chromatography色谱法

2.melan,melano,nigr黑

melanoma黑素瘤melanin黑色素melanophore黑色素细胞

3.xantho,flavo,fla,flavi,lute黄

xanthophyll叶黄素 xanthous黄 色 的,黄 色 人 种 xanthine黄 嘌 呤flavin(e)黄 素flavone黄酮lutein黄体素flavinadeninedinucleotide(FAD)黄素腺嘌呤二核苷酸

4.erythro,rub,rubrm,ruf红

erythrocyte红细胞erythromycin红霉素erythropoietin(EPO)促红细胞生成素

5.chloro,chlor绿,氯

chlorophyll叶绿素chloride氯化物chloramphenicol氯霉素

6.cyan,cyano蓝,青紫色,氰

cyanophyceae蓝藻纲cyanobacteria蓝细菌cyanide氰化物

7.aur,glid,chrys金色

aureomycin金霉素chrysose金藻淀粉chrysanthemum菊花gild镀金

8.leu,leuco,leuk,leuko,blan,alb无色,白色

leucine亮氨酸leukaemia=leucosis白血病bleachingpowder漂白粉albomycin白霉素

三、表示摄食的词素

1.vore食……动物,vorous食……动物的

algivore食藻动物carnivore食肉动物herbivore食草动物omnivore杂食动物

2.phage吃(食)食……生物(体)phagous吃(食)……的

phage=bacteriophage噬菌体phagocyte吞噬细胞zoophage食肉动物saprophage腐食

四、表示方位和程度的词素

1.endo,ento内,在内

endocrine内分泌endocytosis胞 吞 作 用endogamy同 系 交 配endolysin内 溶 素entoderm内胚层

2.ec,ect,exc,extra外,外面,表面

ectoblast外胚层ectoparasite外寄生生物extract抽取,浸出

3.meso中,中间

mesosphere中圈,中层 mesoblast中胚层质

4.intra,intro,inter在内,向内

intraallelicinteraction等位基因内相互作用intracellular(细)胞内的interurban城市之间

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5.centri,centro,medi,mid中心,中央,中间

centrifuge离心centriole中心粒centrosome中心体centrogene着丝基因

6.epi,peri上,外,旁

epidermalgrowthfactor(EGF)表皮生长因子epibranchial上鳃的perilune近月点

7.sub,suc,suf,sug下,低,小

suborder亚目submucosa黏膜下层subclone亚克隆subcellular亚细胞subsection小节,

分部

8.super,supra上,高,超

superconductor超导体superfluid超流体superoxide超氧化物supramolecular超分子的

9.hyper超过,过多

hypersensitive过敏的hyperelastic超弹性的hypertension高血压hyperploid超倍体

10.hypo下,低,次

hypoglycaemia低血糖hypotension低血压hypophysis脑下垂体

11.iso等,相同,同

isoosmotic等渗的isopod等足目动物isotope同位素

12.oligo,olig少,低,寡,狭

oligohaline狭盐性oligogene寡基因oligomer低聚体oligophagous寡食性oligarchy寡

头政治

13.eury多,宽,广

eurythermal广温的euryhaline广盐性eurytopicspecies地理的、生境的广分布种

14.ultra超

ultraacoustics超声学ultrastructure超微结构ultraviolet紫外线

15.infra下,低,远

infralittoral潮下带,远岸的infrahuman类人生物infrared红外线的infrastructure基础

结构

五、表示动物不同器官和组织的词素

1.cephal,capit,cran头,头颅

2.cyte细胞

3.carn,my,mya,myo肉,肌肉

4.haem,haemat,hem,aem,sangul血

5.soma,corp体,身体

6.some,plast体,颗粒

7.hepa,hepat肝 :heparin肝素hepatopancreas肝胰腺hepatocyte肝细胞hepatoma肝癌

8.ren,nephr肾:adrenal肾上腺的nephridia肾管nephron肾单位

9.card,cord心:cardiotoxin心脏毒素cardiovascularcenter心血管中枢electrocardiogram心电图concord一致,和谐

10.ophthalm,ocell,ocul眼:ophthalmology眼科学ophthalmia眼炎ophthalmologist眼科专

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附录1 生物专业英语常见词素

148  

11.branchi鳃:filibranch丝鳃lamellibranch瓣鳃secondarybranchia次生鳃

12.brac,brachi腕,手臂:brachiolaria短腕幼虫brachionectin臂粘连蛋白bracelet手镯

13.dent,odont牙齿:dentin牙质odontphora齿舌odontoblast成牙质细胞

14.plum羽:plumatus羽状的plumule羽绒plumage(鸟的)羽毛

15.foli,foil叶:follicle滤泡foiling叶形foliage叶子foliose多叶的

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附录2 生物专业英语常见词缀

表示无,抗,非的前缀

一、a,an无,非。可以进一步理解为离开,除去,脱去等

1.无

abacteria无菌的,atony无力,anemia贫血(无血之意),abiosis无生命,abrachia无臂畸形,

adacrya无泪,adactylia无指(趾)畸形,adendric无树突的,atrophoderma皮肤萎缩(即无皮

肤营养之意),adiaphoresis无汗症。

2.否定

asymmetric不对称的,asynergy不协调,asystole心搏停止(心脏不收缩),atactic共济失调

的(不协调),asynchronous不同步的,asyllabia拼音不能。

3.离开

aspiration吸引,aberrant迷走的(即离开正常途径的)。

4.An在元音前用ananaerobe厌氧菌,anaesthesia无感觉,麻醉,analgesia无痛法,痛觉消失,anamniotic无羊

膜的,anangioplasia血管发育不全,anapepsia胃蛋白酶缺乏,anaplasia退行发育,anascitic无腹水的,anastigmatic无散光的,anacholia胆汁缺乏。

二、ab去,离开,除

abnormal不正常的(即背离正常的),abapical离尖的,离心尖的(尖以外的,心尖外的),abarticular关节外的,abaxial轴外的,离轴的,abduct绑架,外 展,ablactation断 奶(离 开 奶),abneural神经外的。

三、Ant,anti,对抗,取消,抑制,解除

antagonistic对抗 的,antitoxin抗 毒 素,antibody抗 体,antigen抗 原,antacid抗 酸 剂,antipyretic解热剂,antibiotic抗菌素,antispasmin解痉剂,antiamylase抗淀粉酶,anticoagulant抗

凝的。

四、De向下,减少,降低,除去,否定,离开,解除,脱去等

deacidification去酸 作 用,deactivation灭 活 性,deacylase脱 酰 基 酶,deamination脱 氨 作 用,

deaquation脱水 作 用,deviate背 离,decrease减 少,descend下 降,decompose分 解,decompress减压,deficiency不中,不全,缺乏,deceleration减速度,deformity畸形,变形(非正常形

态之意),degeneration退行性变,变性(即背离正常性质),decentration偏心(即离开中心),

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附录2 生物专业英语常见词缀

150  

decerebrate去大脑decortication去皮质,去皮层,defibrillate除震颤,deficit短缺,deflection偏向,detail详细(de也有表示完全之意)。

五、Dis否定,分开,相反等

disability丧失劳动力,disaggregation感觉综合不能,disassimilation异化作用,dislocation脱

位,disassociation分离,discharge放电,discission挑开术,分裂术,discomfort不舒适disconnect分离,不连接,descrimination辨别(含分开之意),disequilibrium不平衡。

六、Il,im,in,ir非,无,不

1.In非,无,不

inactive无活性的,inability无 能 力,inaccurate不 精 确 的,insoluble不 溶 解 的,inadequate不适当的,inadaptable不适应的,inacidity无酸,inaction无作用,inanimate无生命的,incapacity机能不全,incoagulable不能凝固的,inalimental无营养的。

2.Im为in的变形,在b,p,m,之前用imimpossible不可 能 的,imperforation无 孔,impermeability非 渗 透 性,imbalance不 平 衡,

immature不成熟的,immiscible不可混合的,immobility不活动,impalpable不可触知的,

impotency阳痿(阴茎不能勃起),impure不纯的。

3.Il为in之变形,用于l之前

illhealth健康不佳,illeffect不良作用,illhumor心境不佳,illnourished营养不良的。

4.Ir为in之变形,用于r之前

irregular不规则的,irreversible不可逆的,irreducible不可还原的,不能复归的,不能削减

的,[数]不可约分的,irrespirable不能呼吸的,irresuscitable不可复苏的。

七、Non非,无,不

nonabsorbent非吸收性的,nonacid非酸性的,nonallergic非变态反应性的,nondevelopment不发育,nonconductor非导体,nonimmune非免疫性的,noncongestive非 充 血 性 的,nonmotile无运动的,noninfective非传染性的,非感染性的,nonhemolytic非溶血性的,nonmetal非

金属的,nonsurgical非手术的,非外科的,nonspecific非特异性的,nonviable不能生活的。

八、Un不,非,无

unavoidable不可避免的,unbalance不 平 衡,unknown未 知 的,unconsciousness无 意 识,uncomfortable不舒适的,uncompleted不完全的,uncomplemented未与补体结合的,undifferentiation未分化。

表示数量的前缀

一、基数词

1.uni单一

unilateral单侧的,unipolar单极的,uniaural单耳的,unicentral单中心的,unicellular单细

胞的,unidirectional单向的,unifocal单病灶的,uniocular单眼的,unipara初产妇,unit单

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位。

2.bi,di,diplo,amb,amphi,ampho,二,双

(1)bibiacuminate有二尖端的,biangulate有两角的,bicarbonate重碳酸盐,biauricular双耳

的,biaxial双轴的,bicavity双腔的,biceps二头肌,biconvex双凸的,bivalent双价的,

bivalve双瓣的。(2)didiacetate双醋酸盐,diacetyldiphenolisatin双 醋 酚 酊,diacid二 酸,diamide二 酰 胺,dihybrid双因子杂种,dihydrochlorothiazide,双 氢 氯 噻 嗪,双 氢 克 尿 塞 (一 种 利 尿 药),

diphosphate双磷酸 盐,diad二 分 体,disome双 染 色 体,disomy双 躯 干 畸 胎,二 体 生

物。(3)diplodiplobacillus双杆菌,diploblastic二胚层的,diplococcus双球菌,diploid二倍体,diploneural双重神经支配的,diplopia复视,diplostreptococcus双链球菌。

(4)ambi,amb,ambo二,两侧,复

ambilateral两侧的,ambiopia复视,ambivalent矛盾情绪的(两方面情绪的),ambisexual两性的。

(5)amphi二,两侧,两端

amphibia两栖类,amphichromatic两性反应的,amphigenesis两性生殖,amphinucleolus双核仁,amphipeptone两性胨。

(6)ampho意同amphiamphochromophil双染性的,amphotericin两性霉素,amphoteric两性的。

3.tri三

triangle三角,triad三联症,triacetate三乙酸盐,triacid三价酸,triage伤员拣别分类(国外

急诊室将伤员进行分类,大批伤员选出,有可能抢救存活的病人,先进行抢救,分出轻重缓

急,以便抢救存活更多的病人,此处无三的含义),trialism 三元论,triamine三胺,triatomic三原子的,tribasic三碱价的,tribromide三溴化物。

4.quadra,quadri,tetra,tetro四

(1)quadra,quadri

quadrant四分体,象 限,quadrate四 方 的,quadratus方 肌,quadriceps四 头 肌,quadricuspid四尖的,quadrigeminum四叠体,quadriplegia四肢瘫。

(2)tetra,tetrotetracycline四环素,tetrachloride四氯化物,tetrachlormethane四氯甲烷,tetralogy四

联症,tetrapeptide四肽。

5.penta,pento五

pentacyclic五环的,pentadactyl五指(趾)的,pentose戊糖,pentanucleotide五核苷酸,pentazole五唑,pentobarbital戊巴比妥。

6.hex,hexa六

hexachlorophene六氯酚,hexad六价元素,hexagonal六角形的,hexahydric六氢的,hexane己烷,hexestrol己雌酚。

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7.hept,hepta,sept,七

heptaldehyde庚醛,heptatomic七原子的,七元(价)的,heptavalent七价的,heptose庚糖,

septavalent七价的。

8.octa,octo八

octylacetate辛醋酸酯,octose辛糖,octylene辛烯。

9.nona九

nonan第九日的,nonipara九产妇(第九次生产)。

10.deca十

decacurie十居里(同位素量),decagram 十克,decaliter十升,decameter十米,decanormal十当量的(溶液浓度单位)。

二、数量程度

1.haplo,mono单

(1)haplohaplodermatitis单纯性皮炎,haploid单倍体,haplomycosis单孢子囊菌病,haplopathy无合并症的单纯病,haplopia单视。

(2)monomonocyte单核细胞,mononuclear单核的,mononeuritis单神经炎,monoacid单价酸的,

monoarticular单关节的,monogeny单性生殖,monocelled单细胞的,monoxide一氧化

物,monochromatic单色的,monophase单相。

2.multi,pleo,pluri,poly多

(1)multimultiple多的,multicapsular多 囊 的,multicellular多 细 胞 的,multicenrtric多 中 心 的,

multifetation多胎妊娠,multiform 多 形 的,multilobular多 叶 的,multiparous多 胎 的,

multivalence多价,multiterminal多端的,multinodular多结节的。(2)pleo

pleocaryocyte多核细胞,pleochroic多色的,pleochromocytoma多色细胞瘤,pleocytosis脑脊液细胞增多,pleolysis最大溶血浓度,pleomastia多乳房,pleomorphic多形的。

(3)pluri

pluridyscrinia多种分泌障碍,pluriglandular多腺性的,plurigravida经产的,plurimenorrhea多次行经,plurinuclear多核的,pluripara经产妇,pluripolar多极的,pluripotential多能的。

(4)poly

polycythemia红细胞增多症,polycystic多囊的,polycystoma多囊病,polychylia乳糜过

多,polycylic多 环 的,polyclinic综 合 门 诊 所,综 合 医 院,分 科 医 院,polydipsia烦 渴,

polydontia多牙。

3.demi,hemi,semi半

(1)demidemifacet半面,demilune半月形的,新月细胞。

(2)hemi

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hemiplegia半身 不 遂,hemiprotein半 蛋 白 质,hemipylorectomy幽 门 部 分 切 除 术,hemiscotosis偏侧 盲,hemisection对 切,hemispasm 偏 侧 痉 挛,hemisphere半 球,hemisyndrome偏侧综合征,hemisynergia偏身协同动作,hemitetany半身手足搐搦,hemitoxin半毒素。

(3)semisemiantigen半抗 原,semicanal半 管,semicircular半 环 形 的,semicoma半 昏 迷,轻 昏

迷,semiconscious半清醒的,semidecussation半交叉,semiflexion半屈,semilunare月

骨,semimembrane半渗透膜的,semiplegia半瘫,semipolar半极的,semirecumbent半

卧的,semitransparent半透明的,semicartilaginous半软骨的。

4.holo,pan,完全

(1)holo全部,完全

holoantigen全抗原,holocephalic头部完整的,holodiastolic全舒张期的,holopathy全

身病,holosteosclerosis全身骨硬化,holosystolic全收缩期的,holotetanus全身性破伤

风,holotonia全身肌紧张。(2)pan完全

panagglutination全凝集,panarthritis全关节炎,panarteritis全动脉炎,panesthesia全

感觉 ,pancarditis全心炎,pancytopenia全血细胞减少,pancytosis全血细胞增多。

5.mero,topo局部

(1)mero常指部分

meromicrosomia部分躯干过小,meropia部分盲,merorachischisis部分脊柱裂,meromorphosis再生不全。

(2)topo常指部位

toponarcosis局部麻醉,toponeurosis局部神经机能病,topoalgia局部痛,topodysesthesia局部感觉迟钝,topographic地形的,topology拓扑学。

6.giga,giganto,megamegalo,macro大,巨大

(1)giga,giganto

gigantism巨人症,gigantoblast巨大有核红细胞,gigantocyte巨大红细胞,gigantosoma巨大发育。

(2)mega,megalomegabacterium巨大细菌,megabladder巨 大 膀 胱,megacardia心 肥 大,megacaryoblast成巨核细胞,megacaryocyte巨核细胞,megacecum巨肓肠,megacephalia巨头,megacolon巨结肠,megalencephalon巨脑,megalerythema巨大红斑,megaloblast巨成红细胞

,megalocardia心肥大,megalocephlia巨头,megalodactyly巨趾(指),megaloesophagus巨食管,megaloglossia巨舌。

(3)macro除巨大外,还指长

macrocephalous巨头的,macrocheilia巨唇,macrocheiria巨手,macrochromosome巨染

色体,macroclitoris巨阴蒂,macrococcus巨型球菌,macrocyst巨囊,macrocyte巨红细

胞,macrobiosis长寿,macrocomous长毛的。

7.hyper,over,ultra.过多,超过

(1)hyper过多,超过,上高,重,过度等

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hypertension高血压病,hyperthyroidism 甲状腺功能 亢 进 症,hyperalimentosis营 养 过

度hypertrophy肥大,hyperchloridation供氯过多,hyperchloride过氯化物,hypercholia胆汁过多,hyperchondroplasia软骨增殖过多,hyperiodemia高碘血症,hyperlethal超致

死的,hypermania重 躁 狂 症,hypernormal超 常 的,hyperendemic发 病 率 高 而 持 续 的,

hyperimmunity超免疫,hypertonic高张的。(2)over过度

overaction作用 过 度,overactive活 动 过 度 的,overalimentation营 养 过 度,overcorrection矫正过度,overgrowth生 长 过 度,overhydration水 分 过 多,overdistension膨 胀 过

度,overexertion用力过度,overlapping重叠,overresponse反应过度。(3)ultra超过

ultracentrifugal超离 心 的,ultrafilter超 滤 器,ultramicron超 微 粒,ultrasonic超 声 波

的,ultraviolet紫外线,ultrasound超声。

8.hypo,micro,oligo,sub少,小,不足

(1)hypo低,少,减退,不足,次,过少,不全

hypoacidity胃酸 过 少,酸 过 少,hypoactivity活 动 减 低,hypoalbuminemia血 白 蛋 白 减

少,hypoalimentation营养不足,hypobaropathy低气压病,hypobilirubinemia低胆红素

血症,hypobromite次 溴 酸 盐(hypo化 学 上 译 为 次),hypocalcification钙 化 不 全,hypocalcia钙不足,hypoevolutism发育迟缓,hypoglycemia低血糖症,hypohidrosis少汗,

hyponoia精神迟钝 。

hypo的有其他含意在此一并讨论:

hypocondylar髁下的,hypoderm皮下组织,hypoglossus舌下神经,hypoglottis舌下部,

hypolarynx喉下部,hypospadias尿道下裂,hypophrenium膈下腔,hypotropia下斜视。(2)micro小,细,微

microscope显微镜,microscopist显微镜工作者,microsecond微秒,microsection显微切

片,microslide显微镜玻片,microsoma微粒体,microsphere微球体,microspherocyte小

球形红细胞 ,microsporangium小孢子囊。(3)oligo少,缺少

oligoamnios羊水过少,oligocardia心动徐缓(心跳次数少),oligocholia胆汁过少,oligochromemia血红蛋白过少,oligocythaemia红细 胞 减 少,oligopnea呼 吸 迟 缓(呼 吸 次 数

少),oligosideremia血铁减少,oligospermia精子减少,oligosteatosis皮脂减少,oliguria少尿。

(4)sub不全,不足,次,亚,下

subacetate次醋酸盐(sub化 学 上 译 为 次),subacidity酸 不 足,subacute亚 急 性,subfebrile微热 的,subinvolution复 旧 不 全,subtotal次 全 的,subconsciousness下 意 识 的,

subdivision亚门,subgroup亚群,subfamily亚科,subiodide次碘化物,sublethal亚致死

的,subleukemia亚白血病。

sub除上述含意外,还表示位置在下面。

subabdominal腹下的,subarachnoid蛛网膜下的,subaural耳下的,subscapular肩胛下

的,subclavicular锁骨下的,substratum下层。