細胞核染色體

Characteristics:Chemical,structural,functionalMorphologicalandstructural—shape:varied;size:M—wellorganizedstructure:membrane,organelles,nucleusGolgiapparatusnucleusnucleiChemicals:

water,

inorganicions,smallmolecules,macromoleculesCriticaldifference：Compartmentalization（區(qū)室化）原核細胞prokaryoticcell真核細胞eukaryoticcellThenucleus：a

compartmentofDNA1.Whatisthestructureofthenucleus?

interphase-mitosisphase分裂間期-有絲分裂期2.

Whatarethechemicalcomponentsofthenucleus?3.Whatarethefunctionsofthenucleus?Thefunctionsofthenucleus:StorageofgeneticmaterialsReplicationofDNASynthesisandprocessingofRNAvisibleattheinterphase分裂間期可見Disappearedatthemitosisphase分裂期消失DNAdye-stainedcellsCellsintherootofplantMammaliancellsinculture(DNAfluorescentdye)Muscletissue(H&Estain)Nucleus&Chromosomes1.Nuclearenvelope2.Chromatinandchromosome3.Thefunctionsofthenucleus:3.1DNAreplication3.2DNAdamagerepair3.3genetranscription4.Nucleole5.Nucleus&diseases（CellBiologyChapt.13，14醫(yī)學(xué)細胞生物學(xué)第四章）Nuclearenvelope(Nuclearmembrane)LM：boundaryEM：doublemembranesLightMicroscopeElectronMicroscope(1)nuclearenvelopeandnuclearporeSeparateandalsoconnectthenucleusandthecytoplasm,Nuclearenvelope(nuclearmembranes)Inner&outnuclearmembrane：Amembranethatseparatesthenucleusandcytoplasm.ONM:

linkstothemembraneoftheEndoplasmicReticulumINM:

contactstothenuclearlaminaPerinuclearspace：aspacethatONMandINMsurrounds.

aspaceopentothelumenoftheERPerinuclearspaceAnexpansionofERlumenThenuclearmembranes

(electronmicrograph)Nuclear

poreNuclearpore：theporesonthenuclearmembrane,wheretheINMandONMfusetoeachotherNuclearpore

complex：AproteincomplexthatlinesatandconstructsthenuclearporeThenuclearpores

(electronmicrograph)Thenuclearporecomplex

(electronmicrographs;leftupper:illustratingcartoon)Thefunctionsofthenuclearporecomplex:Aaqueous,

selective,bidirectionalchannel

withdiameter9－25nm,Toseparateandconnectthenucleus

andthecytoplasm1、Smallmolecules<5,000Da(9nm):defusefreely2、Largermolecules(9-25nm):dependontheactivetransportbythenuclearporecomplexQ：whoenterandexitthenuclearpores？（answeraftertoday’slessonsandreviewofChpt4)(or&17）

couldbeanexaminationquestion

opentodiscussiononlinecytoplasmnucleusTheproteindestinedfornucleusNuclearimportreceptorFibersofnuclearporeQ2：Howcanthenuclearporesbeenlarged？（answeraftertoday’slessonsandpreviewofChpt17）

couldbeanexaminationquestion

opentodiscussiononlineNuclear

lamina

AnetshellunderneaththeINMofthehigheucaryocytes,whichconsistsoffibrousproteinsnuclearlamina

(electronmicrographs)Progeria（早老癥）:geneticdeficiencyingenesencodingLAMINs(nuclearlaminaproteins)NormalnuclearlaminaNuclearlaminaofthepatientsToformthenuclearmembraneandtoconstructthechromosomes1、Supportsthenuclearmembrane

ininterphase,andregulatesthede-assemblyandreassemblyofthenuclearmembrane

inmitoticphase2、Providestheanchoragesitesforthechromosomesininterphase,andregulatestheconstructionofchromosomesinmitoticphase

Thefunctionsofthenuclearlamina:轉(zhuǎn)錄翻譯(2)nuclearenvelopeseparatestwoeventsofgeneexpression:transcriptioninthenucleusandtranslationinthecytoplasm,transcriptiontranslation(3)de-assemblyandre-assemblyofthenuclearenvelopeduringmitosisNote:MemorizetheconceptwithoutknowingtoomuchdetailsSummary:

thefunctionsofnuclearmembrane2.Communication1.Isolation(compartmentalization)3.AnchoragesitesforchromosomesChromatin&Chromosome

(1)Chromatines

andchromosomeshavesimilarchemical

compositionbutdistinctmorphologyand

structureMorphology：間期----分裂期Interphase–mitoticphase光鏡下骨骼肌細胞核（蘇木素染色）透射電鏡下超薄切片核內(nèi)染色質(zhì)電鏡整裝樣品呈纖維狀的染色質(zhì)chromatin：interphase：anextendedfineandlonglinearstructure，tanglestoeachother

Aredot-orpatch-likeonultrathinsections

（lateralcut）－h(huán)eterochromatin：beneathINM、peri-nucleolusanddistributed,highelectrondensity－euchromatin：thelightareasbetweenheterochromatin

Whole-mountsample:fibrousCanbestainedunderlightmicroscope;invisiblestructurekaryotypeBandingpatternNucleolarorganizer（rRNAgenes）著絲粒掃描電鏡下分裂中期染色體chromosome:Mitoticphase：coil,condensed,bar-like（visibleunderbothLMandEM）LM：bar-like－karyotype：afterbeing“painted”,thehomologouschromosomesarenumberedandarrangedinpair

toallowidentificationoftheshapesandnumberofchromosomes－bandingpattern：fluorescentdyesstainingtoallowidentificationofthechromosomesScanningEM：Hshaped（sisterchromotidslinkatthecentromere)interphaseM(anaphase)M(metaphase)M(prophase)間期染色質(zhì)分裂中期染色體染色質(zhì)chromatin染色體chromosomeproteinspackage(folding,

coiling,condensing)Chemicalcomposition&structure(1)DNA（doublehelix）(2)ChromosomeproteinsChromatin/chromosome1.histone2.non-histoneDNA 49％histone 49％Non-histone alittleRNA verylittleTheNobelPrizeinPhysiologyorMedicine1910inrecognitionofthecontributionstoourknowledgeofcellchemistrymadethroughhisworkonproteins,includingthenucleicsubstances"

AlbrechtKossel

GermanyUniversityofHeidelberg

Heidelberg,Germanyb.1853

d.1927(2)SpecificsequencesrequiredforexpressionofthegeneticinformationandreplicationofthegeneticmaterialarealignedonDNAmoleculesThesequencesforthe

expressionofthegeneticinformation(genes)

GenomeandgenesThesequencesessentialforDNAreplication(replicationorigins,centromere,telomeres)間期----分裂期Interphase–mitoticphaseTheNobelPrizeinPhysiologyorMedicine1962FrancisHarryComptonCrick

JamesDeweyWatson

MauriceHughFrederickWilkins

"fortheirdiscoveriesconcerningthemolecularstructureofnucleicacidsanditssignificanceforinformationtransferinlivingmaterial"

Genes:thespecificsequencesonDNAGene:

DNAsequencescapableofgeneratingthefunctionalRNA.

Geneistheunitofexpressionofgeneticinformation.

FunctionalRNA

molecules

mRNA：codingRNA(thatencodesproteins)rRNA&tRNA：structualRNA（non-codingRNAs）

manyothernon-codingRNAs

proteintranslationEssentielelementsofachromasomeThreeelementsareessentialforthereplicationanddistribution

ofeachchromosome

multiplereplication

origineswhereDNAreplicationinitiatesduringSphase(interphase)

onecentromereonwhichthespindlefibersattachduringmitosis

twotelomerestheendsofthechromosomeswithlongrepetitive5’TTAGGG3’sequences

Q：Whichpartinthiscartoonmaybemisleading,andWhy

？opentodiscussion(3)ChromosomeproteinsareresponsibleforthepackageofDNAmoleculesandtheregulationofgeneexpression

histonenon-histone間期----分裂期Interphase–mitoticphase組蛋白histoneEqualtoDNA

inquantitySmallmolecularweightRichinthepositivechargeda.a（arginin/lysine,R/K）thatneutralizethenegativechargeofDNA5types： H1

-H1

histone

H2A H2B H3 H4NucleosomehistoneThefunctionsofhistone：1.Toconstructthechromosomes2.Toregulatethegeneexpression

Q：howdotheydoso？非組蛋白non-histoneMuchlessabundantthanhistone

Manytypes

RecognizeandbindwiththespecificsequencesofDNA

Functionsvary： -toconstructthechromosome-toinitiateDNAreplication-toregulatethegeneexpression

(4)DNAmoleculesundergoanorderedpackage

chromatinchromosomeInterphase–mitoticphaseThechromosomalDNApackage

firstlevel:nucleosomes

secondlevel:

30nmfibers

higherlevel:

globalstructure意義:1.使纖長的DNA雙螺旋分子經(jīng)反復(fù)折疊而大大縮短（5cm→5μm）2.有利于轉(zhuǎn)錄和復(fù)制的高效準確進行

包裝(折疊、緊縮)雙螺旋包裝(折疊、緊縮)？？30nm染色質(zhì)纖維串珠狀纖維“beads-on-a-string”(核小體nucleosomes)（常見形式）（doublehelix5cm→2cmnucleosomes）Thepackageofthenucleosomesinto30nm

fiberdependson

1.H12.Thetailsofnucleosomehistone

返回組蛋白H1幫助把相鄰核小體拉在一起,折疊成直徑30nm的規(guī)則結(jié)構(gòu)。H2A、H2B、H3、H4四個亞基的肽鏈尾部伸出，與相鄰核小體發(fā)生作用Higher(global)structure：Loop&

supercoil（0.1cm

→5μm）30nm

fiberfoldsintotheloopsbasedonnon-histonescaffold.

Theloopsextendwhengenestheycontainaretranscribed.襻環(huán)loop一段DNA雙螺旋染色質(zhì)串珠結(jié)構(gòu)染色體上呈伸展狀態(tài)的某個區(qū)段染色體的緊縮狀態(tài)整個中期染色體卡通30nm染色質(zhì)纖維間期和分裂期染色體的包裝(5)DNApackageiscorrelatedwiththeregulationofgeneexpressioneuchromatinheterochromatinInterphase–mitoticphase30nm纖維在DNA轉(zhuǎn)錄和復(fù)制時，以襻環(huán)為單位發(fā)生松解，伸展成串珠狀纖維或DNA雙螺旋Thenucleosomesareremodeledtoexposethedoublehelix.histonetailsaremodified：condensedorde-condensed.heterochromatineuchromatinThenucleus(electronmicrograph)heterochromatineThemostcondensedforminachromosomeininterphase10%sequencesarewrappedinTelomeresandcentromereareconstitutiveheterochromatineCombinedbyalotofproteinsEMexaminationofnucleirevealsthreepredominantstructures:

heterochomatin,euchromatinandthenucleolus.Denselypackedheterochromatinisnotcommonlytranscribed,incontrasttoactive,morelooselypacked,euchromatin.Implications?1.telomeresandcentromere（containnogenes）2.genesilencingChromatinstructurevsgeneexpression雌性動物所有細胞中都僅有1條X染色體?？赡芤驗殡p倍X染色體是致死的，在胚胎發(fā)育過程中1條X染色體通過隨機變成異染色質(zhì)而永久失活。此后，這條失活X染色體遺傳給后代細胞，但在細胞受精后會重新活化為常染色質(zhì)最令人驚異的例子：整條染色體異染色質(zhì)化，X染色體成為巴氏小體Barr小體決定黑毛和黃毛的基因分別位于兩條X染色體。胚胎發(fā)育早期，不同細胞中整條X染色體異染色質(zhì)化，造成不同細胞只含黑毛或黃毛基因。黑斑或黃斑分別來源于這兩種細胞。（這種貓是雌還是雄？）Calico貓的奇麗皮毛：雌性的細胞核中巴氏小體核仁巴氏小體發(fā)生異染色質(zhì)化的X染色體:巴氏小體FigureQ5-15EssentialCellBiology(?GarlandScience2010)Q：whichcellhasmoreactivegenetranscription？(6)Thefunctionsofthechromatine

andthechromosomeThecarriersofgeneticmaterials(1)DNA

replicationanddivision(2)DNA

transcription

Onenewstrand：5→3synthesizedcontinuously－leadingstrandAnothernewstrand：5→3synthesizeddiscontinuously－laggingstrandThereplicationofDNA:DNA

polymerasecatalyzessynthesisoftwoDNAstrandsTelomeraseensurescompleteendreplicationofthelaggingstrand卡通Thetranscriptionofgene:RNA

polymerasecatalyzesmRNAsynthesisreview：NucleusunderEMNucleole1.morphology2.chemicalcomposition3.functions返回(1)

Nucleolushasdistinctchemicalcompositionandmorphology在電鏡超薄切片中可以看到，核仁包括互相不完全分隔的3個部分：1）

纖維中心（fibrillarcenter）呈淺染區(qū)，可有多個。2）

纖維成分（fibrillarcomponent）位于淺染區(qū)周圍，呈直徑為5～10nm致密纖維。3）顆粒成分（granularcomponent）呈致密顆粒，顆粒直徑15～20nm，散布于核仁各處。ThreecomponentsinthenucleolusDensefibrillarcomponentFibrillarcenterGranularcomponent

Chemicalcomposition

proteins80％ RNA11％ DNA8％HumanrRNA

geneslocateat5pairsofchromosomes,chromosome13,14,15,21and22.10chromosomeloopsassembleinthenucleolusBandingpatternNucleolarorganizer（rRNAgenes）ThegenesencodingrRNAaretandemlyarrangedontheloops.間期－分裂期的動態(tài)變化在分裂期，含rRNA基因的DNA襻環(huán)逐漸縮回至相應(yīng)染色體，纖維成分和顆粒成分均分散于核質(zhì)中，整個核仁先是縮小繼而消失。細胞分裂完畢后，在剛誕生的子代細胞中，染色體上含rRNA基因的區(qū)段重新松解和伸展，在這些DNA襻環(huán)周圍，以每一個“核仁組織者”為中心，又組建新的核仁。先是有數(shù)個小核仁形成，隨即

小核仁互相融合成一個或數(shù)個大核仁。1.rRNA

synthesis(transcription)2.rRNA

processing3.rRNA

andproteinsassemblytothesubunitsofribosomes(2)

Thefunctionofthenucleolusisribosomebiogenesis200copiesofrRNAgene,tandemlyarrangedintherDNAloops,aretranscriptedinhigh-speedLinkerDNAOnerRNA

transcriptionunitDirectionofrRNA

polymerizationrDNAloop

pre-rRNAinsynthesisProteinparticleTheChristmastree-liketranscriptionunit-seeninthenucleoleoftheoocyte返回to1.rRNA

synthes