Lac Operon - Concept, Diagram, Notes, Gene Regulation

“Lac operon is an operon or a group of genes with a single promoter that encode genes for the transport and metabolism of lactose in E.coli and ... BiologyBiologyArticleLacOperonRegulationGeneExpression LacOperon-RegulationofGeneExpression “Generegulationcanbedefinedasanykindofalterationinthegenetogiverisetoadifferentexpressionwhichmightresultinachangeinthesynthesizedaminoacidsequence.” Geneexpressionisbasicallythesynthesisofthepolypeptidechainencodedbyaparticulargene.Therefore,wecansaythattheexpressionofthegenecanbequantifiedintermsoftheamountofproteinsynthesisedbythegenes. Let’slearnabouttheregulationofgeneexpressioninprokaryoteswiththeexampleofLacOperon. RegulationofGeneExpression Wecaninferthatthegeneregulationcantakeplaceatvariousstepsofgeneexpressionwhichincludesthefollowing: Replicationlevel–AnyerrorincopyingtheDNAmayresultinanalteredexpression. Transcriptionallevel–Duringtranscription,anyerrorinthepolymerizationmayagainleadtoachangeinexpressionofthegene. Post-transcriptionallevel–Duringthepost-transcriptionalmodificationi.e.,RNAsplicing,theremaybesomechanges. Translationallevel–Duringtranslation,ifthereisanerrorintheattachmentofmRNAtothetRNAmolecules,theremayarisesomechanges. Theregulationoftheexpressionofthegenecanbeexplainedwiththeexampleofanenzyme,sayperoxidaseinbacteria.Thisenzymecatalyzesthehydrolysisofhydrogenperoxidetowaterandoxygen. Now,ifthebacteriaaremovedtoanotherenvironmentwheretheyfailtomanufacturehydrogenperoxide,theenzymenolongerplaysitsrole.Insuchasituation,thebacteriawillnotsynthesizetheenzymeanymore.Thus,wecansaythattheenvironmental,metabolicandphysiologicalconditionregulatestheexpressionofgenes. AlsoRead: ProteinSynthesis GeneRegulationinProkaryotes Generegulationinprokaryotesismostextensivelyobservedattheinitiationoftranscription.Thus,thegeneexpressionduringtranscriptioninitiationisaffectedbyregulation.TheregulationusuallytakesplaceintheexpressionoftheRNApolymeraseatthepromotersite.Thisaffectstheaccessoryproteinswhichbindtotherecognitionsites.Theseaccessoryproteinscanregulatethepromotersiteintwoways: Positiveregulationbyactivators Negativeregulationbyrepressors InOperons,theoperatorissituatedrightnexttothepromoterwheretheregulatorbindstocontrolitsentirefunctioning. LacOperon “LacoperonisanoperonoragroupofgeneswithasinglepromoterthatencodegenesforthetransportandmetabolismoflactoseinE.coliandotherbacteria.” LacOperonConcept GeneregulationinprokaryotescanbeexplainedwiththehelpoftheLacOperonmodel.Herethealterationinphysiologicalandenvironmentalconditionscanbeobservedleadingtoanalterationinexpressioninprokaryotes.ItwasobservedbyJacobandMonod.Thelacoperonconsistsof: Regulatorygenei –Itcodesfortherepressorprotein. zgene–Itcodesforbeta-galactosidasewhichcatalyzesthehydrolysisoflactoseintoglucoseandgalactose. ygene–Itcodesforpermeasewhichregulatesthelactosepermeabilityinthecell. agene–Itcodesfortransacetylasewhichassiststheenzymebeta-galactosidase. Hence,allthesegeneshelpinlactosemetabolism.Inlacoperon,lactoseactsasaninducer.Iflactoseisprovidedinthemediumforthebacteria,theregulatorygeneisactivated.Theinducerwillbindtotherepressorproteinandrenderitinactivewhichallowstranscriptionoftheoperon.Thus,thelacoperonisnegativelyregulatedinthiscase. GeneRegulationinEukaryotes Generegulationineukaryotesisregulatedbytranscriptionalactivatorsandrepressors.TherepressorsbindtospecificDNAsequencesandinhibittranscription.Ineukaryotes,transcriptioninvolvesseveralsteps.Itoccursinboth,nucleus(transcription)andcytoplasm(translation). LacoperonNotes Lacoperoncontainsgenesinvolvedinmetabolism. Thegenesareexpressedonlywhenlactoseispresentandglucoseisabsent. Theoperonisturnedonandoffinresponsetotheglucoseandlactoselevels:cataboliteactivatorproteinandlacrepressor. Thelacrepressorblocksthetranscriptionoftheoperon.Inthepresenceoflactose,itstopsactingasarepressor. cataboliteactivatorproteinactivatesthetranscriptionoftheoperon,onlywhenglucoselevelsarelow. AlsoRead:DifferencebetweengenesandDNA StaytunedwithBYJU’Stolearnmoreabout LacOperonconcept,diagramandRegulationofGeneExpressioninprokaryotesandeukaryotes.Youcanalsorefertothelacoperonnotesmentionedhereforthebetterunderstandingoftheconcept. ShortBiologyQuiz! Q5 PutyourunderstandingofthisconcepttotestbyansweringafewMCQs.Click‘StartQuiz’tobegin! Selectthecorrectanswerandclickonthe“Finish”buttonCheckyourscoreandanswersattheendofthequiz StartQuiz Congrats! VisitBYJU’SforallBiologyrelatedqueriesandstudymaterials Yourresultisasbelow 0outof0arewrong 0outof0arecorrect 0outof0areUnattempted ViewQuizAnswersandAnalysis BIOLOGYRelatedLinks WhatIsALigament FungiExamples FertilizerMeaning FermentationDefinition OmnivoresAnimals ManureMeaning EyeStructure WhatAreMicroorganisms WhatIsPollution WhatIsABiome 2Comments RKRANGASWAMY August29,2019at9:09pm usefullinformation. Reply AditiYadav June3,2020at3:30pm Nice❣️ Reply LeaveaCommentCancelreplyYourMobilenumberandEmailidwillnotbepublished.Requiredfieldsaremarked* * SendOTP DidnotreceiveOTP? 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