细胞的结构细胞的结构StructureofCells课件

1、2.1 细胞的结构细胞的结构(Structure of Cells)All start out life with:细胞膜(Plasma membrane, encircling a region where DNA is stored)细胞质(Cytoplasm) Two types:原核(Prokaryotic)真核(Eukaryotic) 真核细胞 (Eukaryotic Cells)具细胞核和其他细胞器(Have a nucleus and other organelles)真核生物(Eukaryotic organisms)植物(Plants)动物(Animals)原生生物(Prot

2、istans)：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。 动物细胞(Animal Cells)质膜Plasma membrane细胞核Nucleus核糖体Ribosomes内质网Endoplasmic reticulum高尔基体Golgi body小泡Vesicles线粒体Mitochondria溶酶体Lysosome细胞骨架Cytoskeleton中心体 Centrosome

3、植物细胞(Plant Cells)细胞壁Cell wall中央液泡Central vacuole叶绿体Chloroplast质膜Plasma membrane细胞核Nucleus核糖体Ribosomes内质网Endoplasmic reticulum高尔基体Golgi body小泡Vesicles线粒体Mitochondria溶酶体Lysosome细胞骨架Cytoskeleton细胞核(Nucleus)G0和G1期染色体:染色质(Chromosomes at G1 phase: Chromatin)2 nm30 nmCoding (blue) andnon-coding strands (gr

4、ey) of DNAG0和G1期细胞中染色体通常存在的状态(The “usual” state of chromosomes in G0 and G1 cells)7S-G2期染色体:染色质(Chromosomes at S-G2 phase: Chromatin)“Old” coding strand“New” coding strandSpecial DNA binding proteins e.g. cohesins8G2期细胞中染色体通常存在的状态(The “usual” stateof chromosomes inG2 cells (after DNA replication)两个G

5、1期染色质的并排排列，之间有cohesins蛋白连接前期染色体(Chromosomes at prophase)“Old” coding strand“New” coding strandMitotic Chromosome9When cells entry mitosis: Chromatin condense together into a mitotic chromosome10The mechanism of chromosome condensation is not completely understood but notePPPhosphorylation of histone

6、s & proteins in condensin complexCondensincomplexDNA package and chromosome condensation with cell cycle progression from G2 to metaphase Human T-lymphocyte metaphaseKaryotype 46, XY中期染色体(Chromosomes at Metaphase)5 um着丝粒 Centromeres the largest constriction of the chromosome.100,000s of 171 base pai

7、r repeat, called alpha satellite sequencesCentromere associated proteins are bound: KinetochoreSite of attachment of spindle fibersCentromere and Kinetochore端粒 TelomeresAt the tips of chromosomes: Protect Many repeats of the sequence TTAGGGSubtelomeres have more varied short repeats人类全着丝粒探针 （pan-cen

8、tromeric，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Human N-Tert1 cells have intact chromosomes detected by FISH using telomeric and centromeric probesQinghua ShiunpublishedTell me what I am ?染色体是一个物种区分于其他物种的最基本遗传特征不同物种染色体数目不同物种Species 二倍体 # 单倍体 #牛Cattle 6030猪Swine 3819羊Sheep 5427马Horse 6432人H

9、uman 4623鸡Chicken 7839山羊Goat 6030驴Donkey 6231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：？染色体 The Chromosomes染色体在体细胞中成对出现 Chromosomes occurs in pairs in every somatic cell except in the sperm and ovum.一个物种的绝大多数（全部）体细胞，其染色体数目相同Chromosomes numbers are the same in vast majority (every) somatic cell

10、for each species. 染色体 The Chromosomes在二倍体细胞中含2条性染色体 There are 2 sex chromosomes included in the diploid number of the chromosomes.除性染色体以外的染色体统称为常染色体 All of the other chromosomes are referred to as autosomes. 雌性哺乳类的2条性染色体相同 In mammals if the sex chromosomes are alike, XX it results in a female.雄性哺乳类的

11、2条性染色体不同 If the sex chromosomes are different, XY it results in a male.(例外：毛冠鹿)染色体传递：细胞分裂Chromosome transmitting: Cell DivisionMeiosis 减数分裂Is the form of cell division which results reduce the chromosome number from the diploid # to the haploid #.Occurs only in the sex cells, generate sperm and egg.

12、Mitosis 有丝分裂Is the form of cell division which results in the formation of identical daughter cells, keeps the chromosome number constant.Tissue growth and repair.Occurs throughout the body except in the sex cells. 正常有丝分裂AbscissionShi & King, Nature 437:1038-1042, 2005绿色荧光蛋白（Green fluorescence prote

13、in, GFP）-组蛋白H2B融合基因，转入细胞中，使其表达G2ProphaseMetaphaseAnaphaseTelophaseG1SG2 CheckpointSpindle checkpointA mechanism responds to chromosome missegregation? 细胞周期示意图 Cell Cycle ProgressionG1 CheckpointShi, unpublished贝班细胞周期 The Cell Cycle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 The cell cycle is an orderly sequence o

14、f events that occurs from the time when a cell is first formed until it divides into two new cells.Most of the cell cycle is spent in interphase（G1， S 和G2.Following interphase, the mitotic stage of cell division occurs. Division (前、中、后、末期和细胞质分裂G2Early Prophase*Chromosomes condense*Nuclear envelope d

15、isappears*Centrioles move to opposite sides of the cellLate ProphaseSpindle forms and attaches to kinetochores on the chromosomesMetaphase*Chromosomes lined up on equator of spindle*Centrioles at opposite ends of cellAnaphase*Centromeres divide: each 2- chromatid chromosome becomes two 1-chromatid c

16、hromosomes*Chromosomes pulled to opposite poles by the spindleTelophase* Chromosomes decondense* Nuclear envelope reappears* Cytoplasm divided into 2 cellsCytokinesis in Animal CellsIn animal cells, a cleavage furrow begins at the end of anaphase.A band of actin and myosin filaments, called the cont

17、ractile ring, slowly forms a constriction between the two daughter cells.A narrow bridge between the two cells is apparent during telophase, then the contractile ring completes the division.Cytokinesis in animal cellsMitosis in DetailDuring mitosis, the spindle distributes the chromosomes to each da

18、ughter cell.The spindle contains fibers made of microtubules that disassemble and assemble.Centrosomes, that duplicate and separate during interphase, organize the spindle.Centrosomes contain centrioles and asters.Mitosis has four phases: prophase, metaphase, anaphase, and telophase.Mitosis: Maintai

19、ning Chromosome NumberMeiosis: Halving chromosome numberMeiosis: Two DivisionsTwo consecutive nuclear divisions Meiosis IMeiosis IIDNA is NOT duplicated between divisionsFour haploid nuclei are formed Stages of MeiosisMeiosis I Prophase IMetaphase IAnaphase ITelophase IMeiosis IIProphase IIMetaphase

20、 IIAnaphase IITelophase IIChromosome behavior in meiosis I prophase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AMeiosis arrests at diplotene with various defects in synapsis. A-D Diplotene spermatocytes with var

21、ious synapsis defects. E. Statistics of meiosis progression. F. Testicular section stained with H-E. (Red, green and blue marks SCP3, MLH1 foci and centromeres, respectively. n: the number of cells analyzed) 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Meiosis I - StagesProphase

22、IMetaphase IAnaphase ITelophase ICrossing overRandom alignment of chromosomes at metaphase IHomologues separateSister chromatids separate精子发生 SpermatogenesisGrowthMitosis I,Cytoplasmic divisionMeiosis II,Cytoplasmic divisionspermatids (haploid)secondary spermatocytes (haploid)primary spermatocyte (d

23、iploid)spermato-gonium (diploid male reproductive cell)卵子发生OogenesisGrowthMeiosis I,Cytoplasmic divisionMeiosis II,Cytoplasmic division卵子(n) ovum (haploid)初级卵母细胞 (2n) primary oocyte (diploid)卵原细胞 (2n) oogonium (diploid reproductive cell)次级卵母细胞 (n) secondary oocyte (haploid)第一极体(n) first polar body (

24、haploid)三个极体(n) 3 polar bodies (haploid)人类生命周期 Life cycle of humans受精 Fertilization雌雄配子结合、细胞核融合 Male and female gametes unite and nuclei fuse两个单倍体的配子融合形成二倍体的合子 Fusion of two haploid nuclei produces diploid nucleus in the zygote配子融合是随机的 That two gametes unite is random增加了子代的变异 Adds to variation among

25、 offspring导致子代变异的因素 Factors Contributing to Variation Among Offspring前期I同源染色体间的交换 （Crossing over during prophase I中期I染色体在赤道板上的自由排列 （Random alignment of chromosomes at metaphase I配子的自由组合 （Random combination of gametes at fertilizationMITOSIS Occurs in most types of eukaryotic cells.MEIOSISOccurs in f

26、ormation of gametes in eukaryotic cells 有丝分裂和减数分裂比较MITOSIS No pairing of Homologous chromosomesMEIOSISHomologous chromosomes pair & synapsis; crossing over may occur有丝分裂和减数分裂比较MITOSIS Chromosome number is maintained.MEIOSISChromosome number is reduced from diploidy to haploidy.有丝分裂和减数分裂比较MITOSIS One

27、 divisionMEIOSISTwo divisions有丝分裂和减数分裂比较MITOSIS Two daughter cells are produced.MEIOSISFour daughter cells are produced.有丝分裂和减数分裂比较MITOSIS Daughter cells are identical to each other and to parent cellMEIOSISDaughter cells contain varying combinations of chromosomes有丝分裂和减数分裂比较MitosisFunctionsAsexual

28、reproductionGrowth, repair Occurs in somatic cellsProduces clones Mitosis & Meiosis ComparedMeiosisFunction Sexual reproductionOccurs in germ cellsProduces variable offspring有丝分裂和减数分裂比较前期 (Prophase vs. Prophase I) 有丝分裂前期 (Prophase, Mitosis)同源染色体互不影响 (Homologous pairs do not interact with each other.)减数分裂前期I (Prophase I, Meiosis) 同源染色体配对、联会、遗传物质交换（Homologous pairs become zippered to