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1、CuresandClones:StemCellsintheNewsbyChanaPalmer,StanfordUniversityFormillionsofpeoplearoundtheworld,stemcellsoffertheonlyglimmerofhopeforacuretotheirdisease.Stemcellsareaspecialtypeofcellthatmanyscientistsbelievemayonedaybeabletohelpcorrectmanyconditionspreviouslythough
2、tincurable�fromleukemiatoparalysistoParkinson's.Infact,sometypesofstemcellsarealreadybeingusedsuccessfullytohelptreatchildrenwithcertainrarediseases.IllustrationbySueMedaris/UW-MadisonUniversityCommunications.CourtesyofUW-Madison,EmbryonicStemCellshomepageIfstemcellsha
3、vesuchpotentialtorelievesuffering,whyaresomanypeoplesoupsetabouttheiruse?Thereasonisthatthemostpowerfultypeofstemcell�embryonicstem(ES)cells�canonlybeobtainedfromhumanembryos.Manypeoplethinkthatit'swrongtocreateanddestroyhumanembryostotreatdisease.Whatmakesastemcellsos
4、pecialandsopowerful?Therearetwoimportantwaysinwhichstemcellsaredifferentfromothercellsinyourbody.Thefirstisthattheyareunspecialized�thismeansthattheydon'thaveaspecificjobyet,andcantakeonanyoneofmanyspecializedjobslaterintheirlife.Inthisway,stemcellsarelikehighschoolstu
5、dentswhohaveyettodecideontheircareerandhavethepotentialtobeanything,whereastherestofthecellsinyourbodyarealreadyprofessionals.Thesecondimportantqualityofstemcellsisthattheycankeepgrowingandmakingcopiesofthemselvesformanyyears.Here,again,stemcellsareliketeenagers�theyca
6、nhavemanychildrenovermanyyears-whereasmostcellsinthebodyarelikemiddle-agedadultswithonlyafewfertileyearsleft.Areallstemcellsthesame?No,infactthereareseveralquitedifferenttypesofstemcells.Thetypesdifferbywheretheyareinthebodyandbywhattheycanbecome.Themostimportantdistin
7、ctiontomakeisbetweenadultstemcellsandembryonicstemcells.Adultstemcellsarefoundinadultsandchildrenwhileembryonicstemcells(notsurprisingly)arefoundONLYinembryos.Embryonicstemcellsarethemostflexibleandpotentiallyusefultypeofstemcell.Unlikeadultstemcells,whichhavealimitedr
8、angeof"careers"availabletothem,embryonicstemcellscanturnintoalmostanycelltype:blood,heart,liver,bone�EScellsarechildp
