A microspectrofluorometric analysis of nuclear and chloroplast DNA in Volvox☆
[摘要] NucleardivisionimmediatelyfollowsnuclearDNAdoublinginallstagesofthelifecycleexaminedinthegreenalgaVolvox;fluorescencemicrofluorometryofindividualcellsrevealednoevidenceofprolongedaccumulationofnuclearDNApriortomitosisinreproductivecells.SomaticcellnuclearDNAquantityisunaffectedbydevelopmentaleventsingonidiaofthesamespheroid;itremainsconstantfromtheendofcleavageuntilthedeathofthecell.Inreproductivecells,chloroplastDNAreplicationprecedesnuclearreplication.ThesitesofplastidDNAaccumulation,madevisiblebyuseofthefluorochrome4′,6-diamidino-2-phenylindole,increaseinnumberduringtheprolongedgrowthphaseoftheV.carterigonidium.Microspectrofluorometryoffluorochrome-stainedDNAinsitushowsthatplastidDNAincreasesexponentiallythroughoutthisphase.ThecontinuousplastidDNAaccumulationduringgonidialgrowthappearstorepresentaprokaryote-likeinsteadofaeukaryote-likecontrolofDNAsynthesis.MostsomaticcellscontainplastidDNA,andthisdoesnotincreaseinamountduringcolonygrowthandreproduction.MostspermcellsalsocontainplastidDNA,althoughapproximately5%ofsomaticcellsandupto20%ofspermcellshavenodiscernableplastidDNA.ThisisthesecondgroupoforganismsinwhichDNA-freeplastidshavebeenobserved.
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[效力级别] [学科分类] 生物科学（综合）
[关键词] [时效性]
