细胞的结构细胞的结构StructureofCells课件

第二章遗传的物质基础2.1细胞的结构2.2染色体2.3染色体的传递(细胞分裂)第二章遗传的物质基础2.1细胞的结构2.1细胞的结构2.1细胞的结构细胞的结构(StructureofCells)Allstartoutlifewith:细胞膜(Plasmamembrane,encirclingaregionwhereDNAisstored)细胞质(Cytoplasm)Twotypes:原核(Prokaryotic)真核(Eukaryotic)细胞的结构(StructureofCells)Alls真核细胞(EukaryoticCells)具细胞核和其他细胞器(Haveanucleusandotherorganelles)真核生物(Eukaryoticorganisms)植物(Plants)动物(Animals)原生生物(Protistans)：所有不是动物、植物或真菌的真核生物，包括纤毛虫、鞭毛虫等（草履虫、锥虫、疟原虫）真菌(Fungi)锥虫、披发虫等；纤毛虫纲包括喇叭虫、草履虫、四膜虫、钟形虫、栉毛虫等；肉足纲包括放射虫、衣壳虫、沙壳虫、太阳虫、变形虫、有孔虫等；孢子虫纲就一种典型的，是疟原虫。

真核细胞(EukaryoticCells)具细胞核和其他动物细胞(AnimalCells)质膜Plasmamembrane细胞核Nucleus核糖体Ribosomes内质网Endoplasmicreticulum高尔基体Golgibody小泡Vesicles线粒体Mitochondria溶酶体Lysosome细胞骨架Cytoskeleton中心体Centrosome动物细胞(AnimalCells)质膜Plasmamem植物细胞(PlantCells)细胞壁Cellwall中央液泡Centralvacuole叶绿体Chloroplast质膜Plasmamembrane细胞核Nucleus核糖体Ribosomes内质网Endoplasmicreticulum高尔基体Golgibody小泡Vesicles线粒体Mitochondria溶酶体Lysosome细胞骨架Cytoskeleton植物细胞(PlantCells)细胞壁Cellwall质细胞核(Nucleus)细胞核(Nucleus)G0和G1期染色体:染色质(ChromosomesatG1phase:Chromatin)2nm30nmCoding(blue)andnon-codingstrands(grey)ofDNAG0和G1期细胞中染色体通常存在的状态(The“usual”stateofchromosomesinG0andG1cells)8G0和G1期染色体:染色质(ChromosomesatGS-G2期染色体:染色质(ChromosomesatS-G2phase:Chromatin)“Old”codingstrand“New”codingstrandSpecialDNAbindingproteinse.g.cohesins9G2期细胞中染色体通常存在的状态(The“usual”stateofchromosomesinG2cells(afterDNAreplication)两个G1期染色质的并排排列，之间有cohesins蛋白连接S-G2期染色体:染色质(ChromosomesatS-前期染色体(Chromosomesatprophase)“Old”codingstrand“New”codingstrandMitoticChromosome10Whencellsentrymitosis:Chromatincondensetogetherintoamitoticchromosome前期染色体(Chromosomesatprophase)11Themechanismofchromosomecondensationisnotcompletelyunderstoodbutnote…PPPhosphorylationofhistones&proteinsincondensincomplexCondensincomplex11ThemechanismofchromosomeDNApackageandchromosomecondensationwithcellcycleprogressionfromG2tometaphase

DNApackageandchromosomeconHumanT-lymphocytemetaphaseKaryotype46,XYHumanT-lymphocytemetaphaseKa中期染色体(ChromosomesatMetaphase)5um中期染色体(ChromosomesatMetaphase着丝粒Centromeres

thelargestconstrictionofthechromosome.100,000sof171basepairrepeat,calledalphasatellitesequencesCentromereassociatedproteinsarebound:KinetochoreSiteofattachmentofspindlefibers着丝粒Centromeres100,000sof17CentromereandKinetochoreCentromereandKinetochore端粒

TelomeresAtthetipsofchromosomes:ProtectManyrepeatsofthesequenceTTAGGGSubtelomereshavemorevariedshortrepeats端粒TelomeresAtthetipsofchr人类全着丝粒探针（pan-centromeric，Green)和全端粒探针（pan-telomeric，Red)荧光原位杂交检测染色体的完整性HumanN-Tert1cellshaveintactchromosomesdetectedbyFISHusingtelomericandcentromericprobesQinghuaShiunpublished人类全着丝粒探针（pan-centromeric，GreeTellmewhatIam?????染色体是一个物种区分于其他物种的最基本遗传特征TellmewhatIam?????染色体是一个物不同物种染色体数目不同物种Species 二倍体# 单倍体#牛Cattle 60 30猪Swine 38 19羊Sheep 54 27马Horse 64 32人Human 46 23鸡Chicken 78 39山羊Goat 60 30驴Donkey 62 31染色体最少的生物：一种蚂蚁（M.pilosula），单倍体细胞仅1条染色体染色体最多的生物：？？？不同物种染色体数目不同物种Species 二倍体#染色体TheChromosomes染色体在体细胞中成对出现Chromosomesoccursinpairsineverysomaticcellexceptinthespermandovum.一个物种的绝大多数（全部）体细胞，其染色体数目相同Chromosomesnumbersarethesameinvastmajority(every)somaticcellforeachspecies.染色体TheChromosomes染色体在体细胞中成对出染色体

TheChromosomes在二倍体细胞中含2条性染色体Thereare2sexchromosomesincludedinthediploidnumberofthechromosomes.除性染色体以外的染色体统称为常染色体Alloftheotherchromosomesarereferredtoasautosomes.雌性哺乳类的2条性染色体相同Inmammalsifthesexchromosomesarealike,XXitresultsinafemale.雄性哺乳类的2条性染色体不同Ifthesexchromosomesaredifferent,XYitresultsinamale.(例外：毛冠鹿)染色体TheChromosomes在二倍体细胞中含2条性染色体传递：细胞分裂

Chromosometransmitting:CellDivisionMeiosis减数分裂Istheformofcelldivisionwhichresultsreducethechromosomenumberfromthediploid#tothehaploid#.Occursonlyinthesexcells,generatespermandegg.Mitosis有丝分裂Istheformofcelldivisionwhichresultsintheformationofidenticaldaughtercells,keepsthechromosomenumberconstant.Tissuegrowthandrepair.Occursthroughoutthebodyexceptinthesexcells.

染色体传递：细胞分裂

Chromosometransmit正常有丝分裂AbscissionShi&King,Nature437:1038-1042,2005绿色荧光蛋白（Greenfluorescenceprotein,GFP）-组蛋白H2B融合基因，转入细胞中，使其表达正常有丝分裂AbscissionShi&King,NaG2ProphaseMetaphaseAnaphaseTelophaseG1SG2CheckpointSpindlecheckpointAmechanismrespondstochromosomemissegregation?

细胞周期示意图

CellCycleProgressionG1CheckpointShi,unpublished贝班G2ProphaseMetaphaseAnaphaseTel细胞周期

TheCellCycle是一个细胞从其形成到其分裂为2个细胞的一系列按序发生的事件Thecellcycleisanorderlysequenceofeventsthatoccursfromthetimewhenacellisfirstformeduntilitdividesintotwonewcells.Mostofthecellcycleisspentininterphase（G1，S和G2〕.Followinginterphase,themitoticstageofcelldivisionoccurs.Division(前、中、后、末期和细胞质分裂〕细胞周期TheCellCycle是一个细胞从其形成到其G2G2Early

Prophase

*Chromosomescondense

*Nuclearenvelope

disappears

*Centriolesmovetooppositesidesofthecell

Early

Prophase

*ChromosomesLate

Prophase

Spindleformsand

attachesto

kinetochoreson

thechromosomesLate

Prophase

Spindleforms

Metaphase

*Chromosomeslinedup

onequatorofspindle

*Centriolesatopposite

endsofcell

Metaphase

*ChromosomeslinedAnaphase

*Centromeres

divide:each2-

chromatid

chromosomebecomes

two1-chromatid

chromosomes

*ChromosomespulledtooppositepolesbythespindleAnaphase

*Centromeres

divideTelophase

*Chromosomes

decondense

*Nuclearenvelope

reappears

*Cytoplasmdivided

into2cellsTelophase

*Chromosomes

deCytokinesisinAnimalCellsInanimalcells,acleavagefurrowbeginsattheendofanaphase.Abandofactinandmyosinfilaments,calledthecontractilering,slowlyformsaconstrictionbetweenthetwodaughtercells.Anarrowbridgebetweenthetwocellsisapparentduringtelophase,thenthecontractileringcompletesthedivision.CytokinesisinAnimalCellsInCytokinesisinanimalcellsCytokinesisinanimalcellsMitosisinDetailDuringmitosis,thespindledistributesthechromosomestoeachdaughtercell.Thespindlecontainsfibersmadeofmicrotubulesthatdisassembleandassemble.Centrosomes,thatduplicateandseparateduringinterphase,organizethespindle.Centrosomescontaincentriolesandasters.Mitosishasfourphases:prophase,metaphase,anaphase,andtelophase.MitosisinDetailDuringmitosiMitosis:MaintainingChromosomeNumberMitosis:MaintainingChromosomMeiosis:HalvingchromosomenumberMeiosis:HalvingchromosomenuMeiosis:TwoDivisionsTwoconsecutivenucleardivisionsMeiosisIMeiosisIIDNAisNOTduplicatedbetweendivisionsFourhaploidnucleiareformedMeiosis:TwoDivisionsTwocons

StagesofMeiosisMeiosisI

ProphaseIMetaphaseIAnaphaseITelophaseIMeiosisIIProphaseIIMetaphaseIIAnaphaseIITelophaseIIStagesofMeiosisMeiosisIMChromosomebehaviorinmeiosisIprophaseChromosomebehaviorinmeiosis联合复合体（SC）SC:位于两条同源染色体之间，沿纵轴方向延伸；两侧为侧生组分，宽约20-40nm；侧生组分间为中间区，宽约100nm；中间区的中央为中央组分，宽约30nm；侧生组分和中央组分之间有横向排列的纤维，大致成直角相连，称L-C纤细；SC主要由碱性蛋白组成联合复合体（SC）SC:位于两条同源染色体之间，沿纵轴方向延AMeiosisarrestsatdiplotenewithvariousdefectsinsynapsis.A-DDiplotenespermatocyteswithvarioussynapsisdefects.E.Statisticsofmeiosisprogression.F.TesticularsectionstainedwithH-E.(Red,greenandbluemarksSCP3,MLH1fociandcentromeres,respectively.n:thenumberofcellsanalyzed)发现了多种未见报道的减数分裂异常SYCP3:示联会复合体侧轴；MLH1：示重组位点；CREST：示着丝粒人精母细胞减数分裂I前期AMeiosisarrestsatdiploteneMeiosisI-StagesProphaseIMetaphaseIAnaphaseITelophaseICrossingoverRandomalignmentofchromosomesatmetaphaseIHomologuesseparateMeiosisI-StagesProphaseIMeSisterchromatidsseparateSisterchromatidsseparate精子发生SpermatogenesisGrowthMitosisI,CytoplasmicdivisionMeiosisII,Cytoplasmicdivisionspermatids(haploid)secondaryspermatocytes(haploid)primaryspermatocyte(diploid)spermato-gonium(diploidmalereproductivecell)精子发生SpermatogenesisGrowthMito卵子发生OogenesisGrowthMeiosisI,CytoplasmicdivisionMeiosisII,Cytoplasmicdivision卵子(n)ovum(haploid)初级卵母细胞(2n)primaryoocyte(diploid)卵原细胞(2n)oogonium(diploidreproductivecell)次级卵母细胞(n)secondaryoocyte(haploid)第一极体(n)firstpolarbody(haploid)三个极体(n)3polarbodies(haploid)卵子发生OogenesisGrowthMeiosisI,M人类生命周期Lifecycleofhumans人类生命周期Lifecycleofhumans受精Fertilization雌雄配子结合、细胞核融合Maleandfemalegametesuniteandnucleifuse两个单倍体的配子融合形成二倍体的合子Fusionoftwohaploidnucleiproducesdiploidnucleusinthezygote配子融合是随机的Thattwogametesuniteisrandom增加了子代的变异

Addstovariationamongoffspring受精Fertilization雌雄配子结合、细胞核融合M导致子代变异的因素FactorsContributingtoVariationAmongOffspring前期I同源染色体间的交换（CrossingoverduringprophaseI〕中期I染色体在赤道板上的自由排列（RandomalignmentofchromosomesatmetaphaseI〕配子的自由组合（Randomcombinationofgametesatfertilization〕导致子代变异的因素FactorsContriMITOSIS

Occursinmosttypesofeukaryoticcells.MEIOSISOccursinformationof

gametesineukaryoticcells

有丝分裂和减数分裂比较MITOSISMITOSIS

NopairingofHomologouschromosomesMEIOSISHomologouschromosomespair&synapsis;crossingovermayoccur有丝分裂和减数分裂比较MITOSISMITOSIS

Chromosomenumberismaintained.MEIOSISChromosomenumberisreducedfromdiploidytohaploidy.有丝分裂和减数分裂比较MITOSISMITOSIS

OnedivisionMEIOSISTwodivisions有丝分裂和减数分裂比较MITOSISMITOSIS

Twodaughtercellsare

produced.MEIOSISFourdaughtercellsareproduced.有丝分裂和减数分裂比较MITOSISMITOSIS

Daughtercellsare

identicaltoeachotherandtoparentcellMEIOSISDaughtercellscontain

varyingcombinationsofchromosomes有丝分裂和减数分裂比较MITOSISMitosisFunctionsAsexualreproductionGrowth,repairOccursinsomaticcellsProducesclones

Mitosis&MeiosisComparedMeiosisFunctionSexualreproductionOccursingermcellsProducesvariableoffspring有丝分裂和减数分裂比较MitosisMitosis&MeiosisComp前期(Prophasevs.ProphaseI)有丝分裂前期

(Prophase,Mitosis)同源染色体互不影响(Homologouspairsdonotinteractwitheachother.)减数分裂前期I(ProphaseI,Meiosis)同源染色体配对、联会、遗传物质交换（Homologouspairsbecomezipperedtogetherandcrossingoveroccurs.)有丝分裂和减数分裂比较前期(Prophasevs.ProphaseI)有分裂后期减数分裂后期I(AnaphaseI,Meiosis)同源染色体分开(Homologouschromosomesareseparatedfromeachother.)有丝分裂后期/减数分裂后期II(Anaphase/AnaphaseII,Mitosis/Meiosis)姐妹染色单体分开(Sisterchromatidsofachromosomeareseparatedfromeachother)有丝分裂和减数分裂比较分裂后期减数分裂后期I(AnaphaseI,Meio分裂结果(ResultsofMitosisandMeiosis)有丝分裂(Mitosis)2个二倍体细胞(Twodiploidcellsproduced)2个子细胞均与亲代细胞相同(Eachidenticaltoparent)减数分裂(Meiosis)4个单倍体细胞(Fourhaploidcellsproduced)4个子细胞互不相同,且有别于亲代细胞(Differfromparentandoneanother)有丝分裂和减数分裂比较分裂结果(ResultsofMitosisandMe生命的细胞理论（1）1)每种生物都是由1个或多个细胞组成的(Everyorganismisconsistedofoneormorecells)2)细胞是生命的最小单位(Cellissmallestunitoflife)3)生命的延续是以单个细胞的生长和分裂为基础的(Continuityoflifearisesfromgrowthanddivisionofsinglecells)生命的细胞理论（1）1)每种生物都是由1个或多个细胞组成4〕可独自生存或具此潜力Cansurviveonitsownorhaspotentialtodoso5〕可进行高度有序的代谢Ishighlyorganizedformetabolism6〕可感受并对环境的变化作出反应Sensesandrespondstoenvironment7〕具有增殖的潜力Haspotentialtoreproduce生命的细胞理论（2）4〕可独自生存或具此潜力Cansurviveonit第二章遗传的物质基础2.1细胞的结构2.2染色体2.3染色体的传递(细胞分裂)第二章遗传的物质基础2.1细胞的结构2.1细胞的结构2.1细胞的结构细胞的结构(StructureofCells)Allstartoutlifewith:细胞膜(Plasmamembrane,encirclingaregionwhereDNAisstored)细胞质(Cytoplasm)Twotypes:原核(Prokaryotic)真核(Eukaryotic)细胞的结构(StructureofCells)Alls真核细胞(EukaryoticCells)具细胞核和其他细胞器(Haveanucleusandotherorganelles)真核生物(Eukaryoticorganisms)植物(Plants)动物(Animals)原生生物(Protistans)：所有不是动物、植物或真菌的真核生物，包括纤毛虫、鞭毛虫等（草履虫、锥虫、疟原虫）真菌(Fungi)锥虫、披发虫等；纤毛虫纲包括喇叭虫、草履虫、四膜虫、钟形虫、栉毛虫等；肉足纲包括放射虫、衣壳虫、沙壳虫、太阳虫、变形虫、有孔虫等；孢子虫纲就一种典型的，是疟原虫。

真核细胞(EukaryoticCells)具细胞核和其他动物细胞(AnimalCells)质膜Plasmamembrane细胞核Nucleus核糖体Ribosomes内质网Endoplasmicreticulum高尔基体Golgibody小泡Vesicles线粒体Mitochondria溶酶体Lysosome细胞骨架Cytoskeleton中心体Centrosome动物细胞(AnimalCells)质膜Plasmamem植物细胞(PlantCells)细胞壁Cellwall中央液泡Centralvacuole叶绿体Chloroplast质膜Plasmamembrane细胞核Nucleus核糖体Ribosomes内质网Endoplasmicreticulum高尔基体Golgibody小泡Vesicles线粒体Mitochondria溶酶体Lysosome细胞骨架Cytoskeleton植物细胞(PlantCells)细胞壁Cellwall质细胞核(Nucleus)细胞核(Nucleus)G0和G1期染色体:染色质(ChromosomesatG1phase:Chromatin)2nm30nmCoding(blue)andnon-codingstrands(grey)ofDNAG0和G1期细胞中染色体通常存在的状态(The“usual”stateofchromosomesinG0andG1cells)69G0和G1期染色体:染色质(ChromosomesatGS-G2期染色体:染色质(ChromosomesatS-G2phase:Chromatin)“Old”codingstrand“New”codingstrandSpecialDNAbindingproteinse.g.cohesins70G2期细胞中染色体通常存在的状态(The“usual”stateofchromosomesinG2cells(afterDNAreplication)两个G1期染色质的并排排列，之间有cohesins蛋白连接S-G2期染色体:染色质(ChromosomesatS-前期染色体(Chromosomesatprophase)“Old”codingstrand“New”codingstrandMitoticChromosome71Whencellsentrymitosis:Chromatincondensetogetherintoamitoticchromosome前期染色体(Chromosomesatprophase)72Themechanismofchromosomecondensationisnotcompletelyunderstoodbutnote…PPPhosphorylationofhistones&proteinsincondensincomplexCondensincomplex11ThemechanismofchromosomeDNApackageandchromosomecondensationwithcellcycleprogressionfromG2tometaphase

DNApackageandchromosomeconHumanT-lymphocytemetaphaseKaryotype46,XYHumanT-lymphocytemetaphaseKa中期染色体(ChromosomesatMetaphase)5um中期染色体(ChromosomesatMetaphase着丝粒Centromeres

thelargestconstrictionofthechromosome.100,000sof171basepairrepeat,calledalphasatellitesequencesCentromereassociatedproteinsarebound:KinetochoreSiteofattachmentofspindlefibers着丝粒Centromeres100,000sof17CentromereandKinetochoreCentromereandKinetochore端粒

TelomeresAtthetipsofchromosomes:ProtectManyrepeatsofthesequenceTTAGGGSubtelomereshavemorevariedshortrepeats端粒TelomeresAtthetipsofchr人类全着丝粒探针（pan-centromeric，Green)和全端粒探针（pan-telomeric，Red)荧光原位杂交检测染色体的完整性HumanN-Tert1cellshaveintactchromosomesdetectedbyFISHusingtelomericandcentromericprobesQinghuaShiunpublished人类全着丝粒探针（pan-centromeric，GreeTellmewhatIam?????染色体是一个物种区分于其他物种的最基本遗传特征TellmewhatIam?????染色体是一个物不同物种染色体数目不同物种Species 二倍体# 单倍体#牛Cattle 60 30猪Swine 38 19羊Sheep 54 27马Horse 64 32人Human 46 23鸡Chicken 78 39山羊Goat 60 30驴Donkey 62 31染色体最少的生物：一种蚂蚁（M.pilosula），单倍体细胞仅1条染色体染色体最多的生物：？？？不同物种染色体数目不同物种Species 二倍体#染色体TheChromosomes染色体在体细胞中成对出现Chromosomesoccursinpairsineverysomaticcellexceptinthespermandovum.一个物种的绝大多数（全部）体细胞，其染色体数目相同Chromosomesnumbersarethesameinvastmajority(every)somaticcellforeachspecies.染色体TheChromosomes染色体在体细胞中成对出染色体

TheChromosomes在二倍体细胞中含2条性染色体Thereare2sexchromosomesincludedinthediploidnumberofthechromosomes.除性染色体以外的染色体统称为常染色体Alloftheotherchromosomesarereferredtoasautosomes.雌性哺乳类的2条性染色体相同Inmammalsifthesexchromosomesarealike,XXitresultsinafemale.雄性哺乳类的2条性染色体不同Ifthesexchromosomesaredifferent,XYitresultsinamale.(例外：毛冠鹿)染色体TheChromosomes在二倍体细胞中含2条性染色体传递：细胞分裂

Chromosometransmitting:CellDivisionMeiosis减数分裂Istheformofcelldivisionwhichresultsreducethechromosomenumberfromthediploid#tothehaploid#.Occursonlyinthesexcells,generatespermandegg.Mitosis有丝分裂Istheformofcelldivisionwhichresultsintheformationofidenticaldaughtercells,keepsthechromosomenumberconstant.Tissuegrowthandrepair.Occursthroughoutthebodyexceptinthesexcells.

染色体传递：细胞分裂

Chromosometransmit正常有丝分裂AbscissionShi&King,Nature437:1038-1042,2005绿色荧光蛋白（Greenfluorescenceprotein,GFP）-组蛋白H2B融合基因，转入细胞中，使其表达正常有丝分裂AbscissionShi&King,NaG2ProphaseMetaphaseAnaphaseTelophaseG1SG2CheckpointSpindlecheckpointAmechanismrespondstochromosomemissegregation?

细胞周期示意图

CellCycleProgressionG1CheckpointShi,unpublished贝班G2ProphaseMetaphaseAnaphaseTel细胞周期

TheCellCycle是一个细胞从其形成到其分裂为2个细胞的一系列按序发生的事件Thecellcycleisanorderlysequenceofeventsthatoccursfromthetimewhenacellisfirstformeduntilitdividesintotwonewcells.Mostofthecellcycleisspentininterphase（G1，S和G2〕.Followinginterphase,themitoticstageofcelldivisionoccurs.Division(前、中、后、末期和细胞质分裂〕细胞周期TheCellCycle是一个细胞从其形成到其G2G2Early

Prophase

*Chromosomescondense

*Nuclearenvelope

disappears

*Centriolesmovetooppositesidesofthecell

Early

Prophase

*ChromosomesLate

Prophase

Spindleformsand

attachesto

kinetochoreson

thechromosomesLate

Prophase

Spindleforms

Metaphase

*Chromosomeslinedup

onequatorofspindle

*Centriolesatopposite

endsofcell

Metaphase

*ChromosomeslinedAnaphase

*Centromeres

divide:each2-

chromatid

chromosomebecomes

two1-chromatid

chromosomes

*ChromosomespulledtooppositepolesbythespindleAnaphase

*Centromeres

divideTelophase

*Chromosomes

decondense

*Nuclearenvelope

reappears

*Cytoplasmdivided

into2cellsTelophase

*Chromosomes

deCytokinesisinAnimalCellsInanimalcells,acleavagefurrowbeginsattheendofanaphase.Abandofactinandmyosinfilaments,calledthecontractilering,slowlyformsaconstrictionbetweenthetwodaughtercells.Anarrowbridgebetweenthetwocellsisapparentduringtelophase,thenthecontractileringcompletesthedivision.CytokinesisinAnimalCellsInCytokinesisinanimalcellsCytokinesisinanimalcellsMitosisinDetailDuringmitosis,thespindledistributesthechromosomestoeachdaughtercell.Thespindlecontainsfibersmadeofmicrotubulesthatdisassembleandassemble.Centrosomes,thatduplicateandseparateduringinterphase,organizethespindle.Centrosomescontaincentriolesandasters.Mitosishasfourphases:prophase,metaphase,anaphase,andtelophase.MitosisinDetailDuringmitosiMitosis:MaintainingChromosomeNumberMitosis:MaintainingChromosomMeiosis:HalvingchromosomenumberMeiosis:HalvingchromosomenuMeiosis:TwoDivisionsTwoconsecutivenucleardivisionsMeiosisIMeiosisIIDNAisNOTduplicatedbetweendivisionsFourhaploidnucleiareformedMeiosis:TwoDivisionsTwocons

StagesofMeiosisMeiosisI

ProphaseIMetaphaseIAnaphaseITelophaseIMeiosisIIProphaseIIMetaphaseIIAnaphaseIITelophaseIIStagesofMeiosisMeiosisIMChromosomebehaviorinmeiosisIprophaseChromosomebehaviorinmeiosis联合复合体（SC）SC:位于两条同源染色体之间，沿纵轴方向延伸；两侧为侧生组分，宽约20-40nm；侧生组分间为中间区，宽约100nm；中间区的中央为中央组分，宽约30nm；侧生组分和中央组分之间有横向排列的纤维，大致成直角相连，称L-C纤细；SC主要由碱性蛋白组成联合复合体（SC）SC:位于两条同源染色体之间，沿纵轴方向延AMeiosisarrestsatdiplotenewithvariousdefectsinsynapsis.A-DDiplotenespermatocyteswithvarioussynapsisdefects.E.Statisticsofmeiosisprogression.F.TesticularsectionstainedwithH-E.(Red,greenandbluemarksSCP3,MLH1fociandcentromeres,respectively.n:thenumberofcellsanalyzed)发现了多种未见报道的减数分裂异常SYCP3:示联会复合体侧轴；MLH1：示重组位点；CREST：示着丝粒人精母细胞减数分裂I前期AMeiosisarrestsatdiploteneMeiosisI-StagesProphaseIMetaphaseIAnaphaseITelophaseICrossingoverRandomalignmentofchromosomesatmetaphaseIHomologuesseparateMeiosisI-StagesProphaseIMeSisterchromatidsseparateSisterchromatidsseparate精子发生SpermatogenesisGrowthMitosisI,CytoplasmicdivisionMeiosisII,Cytoplasmicdivisionspermatids(haploid)secondaryspermatocytes(haploid)primaryspermatocyte(diploid)spermato-gonium(diploidmalereproductivecell)精子发生SpermatogenesisGrowthMito卵子发生OogenesisGrowthMeiosisI,CytoplasmicdivisionMeiosisII,Cytoplasmicdivision卵子(n)ovum(haploid)初级卵母细胞(2n)primaryoocyte(diploid)卵原细胞(2n)oogonium(diploidreproductivecell)次级卵母细胞(n)secondaryoocyte(haploid)第一极体(n)firstpolarbody(haploid)三个极体(n)3polarbodies(haploid)卵子发生OogenesisGrowthMeiosisI,M人类生命周期Lifecycleofhumans人类生命周期Lifecycleofhumans受精Fertilization雌雄配子结合、细胞核融合Maleandfemalegametesuniteandnucleifuse两个单倍体的配子融合形成二倍体的合子Fusionoftwohaploidnucleiproducesdiploidnucleusinthezygote配子融合是随机的Thattwogametesuniteisrandom增加了子代的变异

Addstovariationamongoffspring受精Fertilization雌雄配子结合、细胞核融合M导致子代变异的因素FactorsContributingtoVariationAmongOffspring前期I同源染色体间的交换（CrossingoverduringprophaseI〕中期I染色体在赤道板上的自由排列（RandomalignmentofchromosomesatmetaphaseI〕配子的自由组合（Randomcombinationofgametesatfertilization〕导致子代变异的因素FactorsContriMITOSIS

Occursinmosttypesofeukaryoticcells.MEIOSISOccursinformationof

gametesineukaryoticcells

有丝分裂和减数分裂比较MITOSISMITOSIS

Nopairingof