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英语四级阅读专项指导训练附答案2017年英语四级阅读专项指导训练附答案Nothingintheworldisdifficultforonewhosetshismindtoit.以下是小编为大家搜索整理的2017年英语四级阅读专项指导训练附答案，希望能给大家带来帮助!更多精彩内容请及时关注我们应届毕业生考试网!HenryIIIdidn'tknowmuchaboutbiology.Hewentthroughsixwivesbackinthe1500s,lookingforonewhocouldbearhimason.Scientistsnowknowthatit'sthefather'ssperm,notthemother'segg,whichdetermineswhetherababyisaboyoragirl.AndlastweekresearchersattheGeneticsandIVFInstitute,aprivatefertility(生育能力)centerinVirginia,announcedanewtechniquethatwillallowparentstochoosethesexoftheirbaby-to-be,beforeithasevenbeenconceived.ThescientistusedatinylaserdetectortomeasuretheDNAinmillionsofspermcellsastheypasssinglefilethroughanarrowtube,likecattlebeingherdedthroughacorral(牲口栏).Inastudypublishedlastweek,"girlsperm,"whichhasmoreDNA—thegeneticmaterial—ineachcell,wascollected,while"boysperm"wasdiscarded.Andwhenpurifiedgirlspermwasusedtoimpregnate(使受孕)agroupofmothers,15of17resultingbabiesturnedouttobegirls.Theresearcherssaythat"sexselection"canalsodoubleamother'schanceofhavingasonandcanbeusedtoavoidgeneticdiseasesthataffectonlyonegender,suchashemophilia(血友病).Butsomeexperts,likeNewYorkUniversityfertilityspecialistDr.JamieGrifo,worrythatsexselectioncouldleadtoakindofinuteri(子宫)discrimination,especiallyincultureswheresonsareconsideredsuperiortodaughters."It'svaluingonegender'overanother,"Grifosays."Idon'tthinkthat'ssomethingweshouldbedoing."Sofar,patientsattheinstitutehavebeenaskingforbothboysandgirls,inorderto"balance"theirfamilies.Andsomeethicsexpertssaythat'sfine,aslongasparentsarejustlookingforalittlegendervariety."Ifyouhavethreeboys,andyouwantagirl,"saysUniversityofTexasreproductive-lawprofessorJohnRobertson,"that'snotgenderbiasatall."练习题：Choosecorrectanswerstothequestion:1.TheDNAinthespermcellscanbemeasured______.A.inthesamewayhowthecattleareherdedB.whentheypassthroughatubeonebehindtheotherC.aftertheypassthroughalasertubeD.wh
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