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1、MethodsinMolecularBiologyMethodsinMolecularBiologyTMVOLUME247DrosophilaDrosophilaCytogeneticsCytogeneticsProtocolsProtocolsEditedbyEditedbyDarylS.HendersonDarylS.HendersonDrosophilaChromosomes11TheChromosomesofDrosophilamelanogasterDarylS.Henderson1.IntroductionDrosophilahavet
2、wobasicformsofchromosomes—mitoticandpolytene—thathavevastlydifferentmorphologiesandcellularroles.Polytenechromo-somesarefoundininterphasenucleiofdifferentiatedcells,beingespeciallyprominentincertaintissuesofthelarvaandadultovary.Theyareproducedbyrepeatedroundsofchromosomerepli
3、cationunhitchedfromnucleardivisioninaprocesstermed“endoreplication.”Amongthelargestandmostfamiliarofpolytenechromosomesarethoseofthelarvalsalivarygland,whichcanconsistof>2000sisterchromatidstightlyalignedinregister.Suchscaled-upchromo-somespermitproductionoflargequantitiesofge
4、neproductsinanarrowdevelopmentalwindow.Thehighlycompactmitoticchromosomes,foundinproliferatingtissues(e.g.,thelarvalcentralnervoussystem[CNS],imaginaldiscs,ovaries,andtestes),aregenome-packagingvehiclesthat,inassociationwiththespindleapparatus,functiontotransmitcompletecopieso
5、fthegenomebetweenmotheranddaughternuclei.Meioticchromosomesalsocanbecat-egorizedasmitoticchromosomes,andsomeoftheiruniquepropertiesaretouchedoninChapters2–5(forrecentreviews,seerefs.1–3).Justasmitoticandpolytenechromosomesservedifferentfunctionsinthefly,theyareexploitedbydroso
6、philistsfordifferentpurposes.Thelargesizeanddistinctivebandingpatternsofsalivaryglandpolytenechromosomes—Darlingtonlikenedthemto“contortedearthworms”(4)—makethemanexcel-lentmaterialonwhichtolocategenesandgeneproductsinsitu(seeChapters13–15)ortofinelymapthebreakpointsofchromoso
7、malaberrations(seeChapters12–13).TheriseofDrosophilamelanogastertopreeminenceasanexperimen-talorganismowesmuchtothesegiantchromosomes.MitoticchromosomesareusefulforinvestigatingbasicquestionsofmitoticandmeioticcellbiologyFrom:MethodsinMolecularBiology,vol.247:DrosophilaCytogen
8、eticsProtocolsEditedby:D.S.Henderson©HumanaPressInc.,Totowa,N