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RNAWhatisRNA?RNAisabiologicalmacromoleculethatservesaAtypicalmammaliancellcontains10–30pgtotalnumberofdifferentfunctions.MessengerRNARNA.ThemajorityofRNAmoleculesaretRNAsand(mRNA),transcribedfromDNA,servesasatemplaterRNAs.mRNAaccountsforonly1–5%ofthetotalforsynthesisofproteins.ProteinsynthesisiscarriedcellularRNAalthoughtheactualamountdependsonoutbyribosomes,whichconsistofribosomalRNAthecelltypeandphysiologicalstate.Approximately(rRNA)andproteins.Aminoacidsforproteinsynthesis360,000mRNAmoleculesarepresentinasinglearedeliveredtotheribosomeontransferRNA(tRNA)mammaliancell,madeupofapproximately12,000molecules.RNAsarealsopartofriboproteinsdifferenttranscriptswithatypicallengthofapproxi-involvedinRNAprocessing.mately2kb(Tables1and2,page46).SomemRNAsInaddition,manyvirusescontainRNAastheircompriseasmuchas3%ofthemRNApoolwhereasgenomeinsteadofDNA,andRNAspeciescalledothersaccountforlessthan0.01%.These“rare”orribozymescatalyzebiochemicalreactions,similarto“lowabundance”messagesmayhaveacopyenzymes.SinceRNAisabletoperformfunctionsnumberofonly5–15moleculespercell.However,usuallyassociatedwithDNAandproteins,ithastheserarespeciesmayaccountforasmuchasbeensuggestedthatRNAwastheoriginalbiological11,000differentmRNAspecies,comprising45%ofmolecule,withsubsequentevolutionofDNAandthemRNApopulation(Table3,page46.)*proteins.*Formoreinformation,seereference1.Whilethegenesofanorganismarerelativelyfixed,RNasesareverystable,donotrequirecofactors,arethemRNApopulationrepresentshowgenesareeffectiveinverysmallquantities,andaredifficulttoexpressedunderanygivensetofconditions.Analysisinactivate.RNasecontaminationcancomefromofRNAbyhybridizationtechnologies,includinghumanskinanddustparticles,whichcancarrynorthernblottingandmicroarrayanalysis,orbybacteriaandmolds.IsolationandanalysisofRNART-PCRcanprovideagoodreflectionofanthereforerequiresspecializedtechniques.organism’sgene-expressionprofile.ThischapterdescribesproceduresforsuccessfulComparedtoDNA,however,RNAisrelativ
