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1、Thefundamentalproblemofchemicalphysiologyandofembryologyistounderstandwhytissuecellsdonotallexpress,allthetime,allthepotentialitiesinherentintheirgenome.-FrangoisJacobandJacquesMonod,articleinJournalofMolecularBiology,1961RegulationofGeneExpression28.1Principlesof6eneRegulation11164.
2、Proteinsynthesis(translation)28.2RegulationofGeneExpressioninBacteria11265.Posttranslationalmodi-ficationofproteins6.Proteintargetingandtransport28.3RegulationofGeneExpressioninEukaryotes11367.ProteindegradationTheseprocessesaresummarizedinFigure28-1.Wefthe4,000orsogenesinthetypicalb
3、acterialhaveexaminedseveralofthesemechanismsinpreviousgenome,ortheperhaps29,000genesinthehumanchapters.PosttranscriptionalmodiflcationofmRNA,bygenome,onlyafractionareexpressedinacellatprocessessuchasalternativesplicingpatterns(seeanygiventime.SomegeneproductsarepresentinveryFiS.26-22
4、)orRNAediting(seeFigs27-10,27-12),canIargeamounts:theelongationfactorsrequiredforpro-affectwhichproteinsareproducedfromanmRNAteinslmthesis,forexample,areamongthemostabun-transcriptandinwhatamounts.Avarietyofnucleotidedantproteinsinbacteria,andribulose1,5-bisphosphatesequencesinanmRNA
5、canaffecttherateofitsdegrada-carboxylase/oxygenase(rubisco)ofplantsandphoto-tion(p.1048).Manyfactorsaffecttherateatwhichs;ntheticbacteriais,asfarasweknow,themostabun-anmRNAistranslatedintoaprotein,aswellasthedantenzymeinthebiosphere.Othergeneproductsposttranslationalmodiflcation,targ
6、eting,andeventualoccurinmuchsmalleramounts;forinstance,acellmaydegradationofthatprotein(Chapter27).containonlyafewmoleculesoftheenzymesthatrepairOftheregulatoryprocessesillustratedinFigure28-1,rareDNAlesions.Requirementsforsomegeneproductsthoseoperatingattheleveloftranscriptioninitia
7、tionarechangeovertime.Theneedforenzymesincertainthebestdocumentedandtheseareamajorfocusofmetabolicpathwaysmaywaxandwaneasfoodsourcesthischapter;othermechanismsarealsoconsidered.changeoraredepleted.Duringdevelopmentofamulti-Researcherscontinuetodiscovercomplexandsome-cellularorganism,
8、someproteins
