ABSTRACT
TheabilitytoextractandanalyzeDNAfromplanttissuesisanessentialaspectofplant
molecularbiologyandmaybedividedintotwostages.Inthefirststage,plantcellsare
disruptedtoreleasetheDNA.Thisisacriticalstage.inthatfailuretodisruptallofthecells
inthetissueortoprotecttheDNAduringdisruptionmaygreatlyreducethefinalyieldof
DNA.ItisatthispointthatadecisionmustbemadewhethertoisolatetotalDNAortoobtain aspecificDNAfractionfromthenucleus,chloroplast,ormitochondria.TotalDNAis
acceptableforanalysisofnucleargeneswithoutcloselyrelatedorganellargenes.orfor
organellargeneswithoutcloselyrelatednuclearhomologues.Fractionationofthenuclearand
organellargenomesmaybeusefulforassigningagenetoaparticulargenome.foravoiding
cross-hybridizationofrelatedgenes,andforgeneratingorganelle-specificlibrariesforclon-
ing. Inthesecondstage,theDNAisextractedawayfromtheothercellularconstituentssuch
asproteins.carbohydrates,membranes.andcellwalls.Itisimportantatthisstagetoensure
thatsignificantamountsofDNAarenottrappedinthecelldebris,andthattheDNAis
completelydissociatedfromproteinsandothercontaminantsthatmightcopurifyandinterfere
withsubsequentanalyses. AnumberofdifferentmethodsforpurifyingplantDNAhavebeendescribed. 1·7Itis
beyondthescopeofthischaptertoconsidereachmethodandcomparerelativeadvantages
anddisadvantages;however.somegeneralconsiderationsthatmightbeappliedwhenevalu-
atingaparticularmethodare:
I.Willitworkwithmytissue?Sometissueshavehighlevelsofnucleaseorpolyphenol
oxidase.DNAisolationfromthesetissuesmayrequireadditionalstepsandprecautions notnecessarywithmoretractabletissues.
