Treść książki
Przejdź do opcji czytnikaPrzejdź do nawigacjiPrzejdź do informacjiPrzejdź do stopki
8
AncientDNAandGeneticEngineering
Inthisrespect,itisimpossiblenottomentiontheworkofFrançoisJacob
andJacquesMonod,bothworkingatthePasteurInstituteinParisżThey
werestudyinggenesinvolvedinmetabolismoflactoseinthebacterium
EscherichiacoliżTheyfoundthatthesegenes,lacZ,lacYandlacA,coding
respectivelyforβ-galactosidase,permeaseandtransacetylase,arelocated
closetoeachotherontheE.colichromosomeandaretranscribedona
singlemessengerRNA(mRNA)moleculeżTranscriptionstartsattheelement
calledpromoter,recognizedbytheRNApolymeraseżTranscriptiondepends
ontwoothergenes,theoperatorandtheregulatorżTheoperatorislocated
closetothefrststructuralgene(lacZ),whiletheregulatorisagenecoding
forarepressor,aproteinthatbindstheoperatorandpreventstheonsetof
transcriptionintheabsenceoflactoseżThepromoter,operatorandstruc-
turalgenesformtheso-calledoperonżTranscriptionofthelactoseoperon
occursonlyintheabsenceofglucose,thepreferablecarbonsource,andin
thepresenceoflactosebeinganinhibitoroftherepressorżFrançoisJacob
andJacquesMonodtogetherwithAndréLwofwerejointlyawardedthe
NobelPrizeinPhysiologyin1965ufortheirdiscoveriesconcerninggenetic
controlofenzymeandvirussynthesis”ż
Thefollowingyearsbroughtfurtherinformationonthestructureand
functionofgenomesżItwasfoundthatineukaryotes,themajorityofgenes
arenotcontinuousżTheyarecomposedofuexons”anduintrons”żTheyare
transcribedintopre-mRNA,whichundergoestheprocesscalledusplicing”,
carriedoutbysmallnuclearribonucleoproteins(snRNPs)whichbindto
boththe5’and3’endsoftheintronandcausetheintrontoformaloopż
Theintronisthenremovedfromthesequenceandthetworemaining
exonsarelinkedtogetherż
Atthebeginningoftheseventies,anewbranchofgeneticsnamed
geneticengineeringdevelopedżItbecamepossibletointroduceprecise
changesingeneticmaterialandtotransfergenesfromoneorganismto
anotherżTheclassicexampleofausefulgeneticmanipulationisthecon-
structionofabacterialstraincontainingthehumangenecodingforinsulinż
InsulinisadrugirreplaceableindiabetestreatmentżPreviously,itwas
acquiredfromthepancreasesofpigsandcows,nowitiseasilyavailableby
extractionfrombacteriagrowinginhugefermentersżTheemergence
ofgeneticengineeringarousedsomeconcernsconnectedwiththesafetyof
geneticengineeringexperimentsżItwastheoreticallypossibletousethese
