cDNA vs Genomic DNA | BioChain Institute Inc.

The DNA residing in chromosomes inside the nucleus, with all the biological information to be transferred to the next generation, is calledgenomic DNA(gDNA). ApproveTheCookies Thiswebsiteusescookiestoimproveyouruserexperience Iaccept Readmore Thestorewillnotworkcorrectlyinthecasewhencookiesaredisabled. HomeBlogcDNAvsGenomicDNAcDNAvsGenomicDNA:TheRelationshipandDifferencesinGenomicDNAandComplimentaryDNA-BLOG-DNA:theBuildingBlockofLife Deoxyribonucleicacid,(DNA)isthemoleculethatcarriestheinstructionsforallaspectsofanorganism’sfunctions,fromgrowth,tometabolism,toreproduction.Inlivingorganisms,mostoftheDNAresidesintightlycoiledstructurescalledchromosomes,locatedinsidethenucleusineachcell.DNAismadeupoffourdifferentbuildingblocks,callednucleotides,whichareeachmadeupofoneoffournitrogenousbasesdemonstratedinFigure1.Thesearethepurines:guanine(G)andadenine(A),andthepyrimidines:thymine(T)andcytosine(C).Thesenucleotidesarecoupledtoadeoxyribosesugarandareabletobindtootherdeoxyribosesugarsviaphosphatelinkagestoformlongchains,someofwhichcanbewellover100,000,000moleculeslong.SinceeachdeoxyriboseinaDNAchainiscoupledtooneofthefournitrogenousbases(G,A,T,orC),theselongchainscancarryinformation. Groupsofthreenucleotidesformthesmallest,butmostwell-defined“words”intheDNAlanguage.These“words”arecalledcodons.Codonsareusedtocallforspecificaminoacidstobebondedtogethertoformproteins.Forinstancethecodonadenosine-adenosine-guanosine(AAG)callsfortheaminoacidlysine(lys)tobeincorporatedintoaproteinmolecule.ThecodonAGGcallsfortheaminoacidarginine(arg).SotheAAG-AGGwouldcallforonelystobecoupledtoonearginagrowingproteinchain.Therearealsocodonsthat,undertherightcircumstances,callforaproteintobegintobeformed(startcodons),orforaproteinchaintobefinished(stopcodons).Asyoucanseefromthissimpleexample,DNAcancarryamassiveamountofinformation. Image:DNAandRNAcodontables:SourceWikipedia WhatareGenomicandComplimentaryDNA? Theinitialcomponentinbothofthesebiopsymethodsistheextractionofmattertobeanalyzed.(Right:ComparisonofBiopsyMethodsGenNews). TheDNAresidinginchromosomesinsidethenucleus,withallthebiologicalinformationtobetransferredtothenextgeneration,iscalledgenomicDNA (gDNA).Thewords“genome”and“genomic”comefromtheword“gene”.Ageneisasetofcodonsthatspecifyaspecificproteinchain,alongwiththeassociatedstartandstopcodons.Thewordgenomeisanextensionofthisconceptandmeansthecollectionofallgenesandotherinformationcontainedinsidethenucleiofanorganism’scells.Often,whentheword“DNA”isusedwithoutfurtherclarification,itreferstogDNA. Innature,theprocessforinformationtobepassedonfromDNAcanoccurthrougheitherreplicationorgeneexpression.Therearesomeimportantfactorstonote: DNAcancopyitselfinaprocessknownasreplication,usingDNApolymerase. InformationfromDNAispassedthroughmessengerRNA(mRNA),whichcontainssetsoffournucleotides(uracil,adenine,guanine,andcytosine). mRNAisproducedwhenenzymes,suchasRNApolymerase,bindtospecificgenesandcopytheirinformationintoRNAusingaribosesugar(notdeoxyriboseasinDNA).Thisprocessiscalledtranscription. RibosomesassemblearoundmRNA,creatinganaminoacidchaintocreatespecificproteins.Thisiscalledtranslation. Duetotheribosesugarchains,mRNAisshortlived.Itisdesignedtoconveyinformationfromthechromosomesinthenucleustothemachinerythatmakesproteins. mRNAdegradesrapidlyafterithascompletedit’spurpose. Figure1:Adeninebindstothymine;guaninebindstocytosine. ThiscreatesthedoublehelixstrandsofDNA(NatureEducation). Figure2:the“CentralDogma”ofbiologyfailstotakereversetranscriptionintoaccount(ResearchGate). Initially,itwasobservedthatgDNAwasalwaysreadandtranscribedintomRNA,whichguidedproteinformationandthenwasdisposed.ThenotionthatinformationmightalwaysflowfromDNAtoRNAtoproteinwassomewhatjokinglyreferredtoastheCentralDogmaofmolecularbiology.Callingitthatchallengedscientiststofindexceptionstothisrule. Virologistseventuallydidfindonesuchexception.Retroviruseswerediscoveredtohavemechanismsfor“reversetranscription.”ThismeansthattheycantakeRNAchainsandproduceDNAchainsfromthem.Inthisway,duringreversetranscription,informationflowedbackwardsfromRNAbacktoDNA.DNAthatarisesfromthisprocessiscalled complementaryDNA (cDNA).cDNAiseitherproducedbysomevirusesorsynthesizedinlaboratories.ThevariousprocessesinvolvedincreatingDNAandRNAaredemonstratedinFigure2. TheFunctionsofgDNAandcDNA cDNAcanbedescribedasgDNAwithoutallthenecessarynoncodingregions,whichishowitgetsitsnameascomplimentaryDNA. AprimarydistinctiontobemadebetweencDNAandgDNAisintheexistenceofintronsandexons. Introns arenucleotidesingenesthatdon’thaveanycodingsequences.Generally,intronsaresplicedout,or“editedout”ofRNAinthetranscriptionprocessbeforeproteinsarecreated.Itshouldbenotedthatprokaryotesarenotcapableofsplicingoutintrons. Exons areanecessarypartofthecodingsystem,beingretainedafterintronsaresplicedout.ThisisdisplayedinFigure3. Exitrons areintronsthatarenotsplicedout,despitecontainingnocodingsequences. Figure3:Introns(blue)aresplicedoutfromRNAtocreatemRNAforproteinsynthesis(Daycd) WhenscientistsuseviralenzymestomakecDNAfromRNAisolatedfromthecellsandtissuesthattheyarestudying,itdoesnotcontainintronsduetobeingsplicedoutinmRNA.cDNAalsodoesnotcontainanyothergDNAthatdoesnotdirectlycodeforaprotein(referredtoasnoncodingDNA).Lastly,notallgenesinthegDNAarebeingtranscribedintomRNAatanygiventime.Asaresult,cDNAwillonlycontaingenesthatareactivelybeingusedbyaspecificcellortissueatapointintime.ThereismuchlesstotalinformationincDNAthangDNA,butwhatinformationremainscanbealotmorerelevanttowhataresearcherislookingatsinceitdoesn’tcontainsequencesthatareunnecessarytothefunctioningandreplicationoftheDNA. Onceisolated,gDNAcanbeusedtomakegenomiclibrariesforDNAsequencing,fingerprinting,differentiationandotherapplicationswithbothclinicalandresearchfields. cDNAcanalsobeusedalsobeusedtomakecDNAlibraries,permanentcollectionsofcDNAthatcanbecopiedand/orstoredlongterm,anditiscommonlyusedtocloneeukaryoticgenesinaprokaryote.Thiswayaproteinexpressedinaeukaryoticorganismcanbeintroducedintoaprokaryote.ForthisprocesscDNAisusedovergDNA,sinceprokaryotescannotspiceoutintronscontainedingDNA. InordertoisolatecDNA,firsttheRNAofanorganismmustbeisolated.Then,usingareversetranscriptaseenzyme,cDNAcanbemade.Thisistheprocessretrovirusesusetoincorporateintotheirhost’scells.Retroviruses,suchasSimianImmunodeficiencyVirus(SIV)andAvianMyeloblastosisVirus(AMV),usetheircDNAtoproducemRNAinthehost,leadingtotheproductionofviralproteins.ThisispossiblebecauseretrovirusesuseRNAastheirgenomicmaterialinsteadofDNA,anditisreversetranscribedintothecDNA,whichthenundergoesnormaltranscriptionandleadstotheviralproteininthehost.ThelifecycleofaretrovirusisshowninFigure4. Figure4:Aretrovirususesreversetranscriptiontointegrateintothehostgenome(EssentialCellBiology). CustomandPremadegDNAandcDNAAvailableatBioChain BioChainprovidesaccesstoacomprehensive,well-documentedtissuebankcontainingisolatedsamplesthathavebeentestedforcontaminants.Aspartofrigorousqualitycontrol,gDNAsamplesaretestedbyspectrophotometerandelectrophoresis,withconcentrationdeterminedbyUV260measureandplantconcentrationdeterminedbypicogreenmeasurement.AllgDNAistreatedwithRNasetoeliminateallRNA. GenomicDNAcomesfromuniquesources,includinghundredsofhealthy/diseasedorgantissuefromhumans,animals,andplants.ThegDNAhasapplicationsrangingfromSNPanalysis,methylationstudies,copynumbervariation(CNV)analysis,comparativegenomichybridation(CGH),SouthernBlotting,NextGenerationSequencing,andPCR. ShoptheLargestTissuecDNASelectionintheMarket BioChain’scDNAsamplesaresynthesizedusingtotalRNAisolationatthefacilitywithmodifiedtechniquestoensureconsistency.cDNAundergoesbothvisualinspectiondetectingintactbandsofribosomalDNA,andtestedbypuritywithaspectrophotometer.ThefirststrandissynthesizedusingMMLVreversetranscriptasewithlowRNaseHactivity,withanoligodTprimertoensurepresenceoftheentirecDNA. Sourcesoriginatefromavarietyofanimal,plantmatter,andhuman/fetaltissue(includinghealthyanddiseasedorgans).Documentationonclinicalhistoryoftissuesisavailable.ThecDNAcanbeusedforPCR,genediscovery,analysisormRNA,andcloningamongothers. AuthorBioChainInstituteInc. Likethisblog?Talktoanexpert! ContactUs