生物专业英语教学 细胞的繁殖.ppt

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1、Unit3 Cellular Reproduction:Mitosis and Meiosis,WarmingupWords and phrasesText AnalysisSimple exercises,Contents,Warmingup,有丝分裂:,无丝分裂:,减数分裂:,一种特殊方式的有丝分裂,细胞增殖方式,与体细胞的形成有关,不出现纺缍体，没有染色体等变化。如蛙的红细胞。,有丝分裂和减数分裂的比较,比较,有丝分裂,减数分裂,不同点,相同点,分裂后形成(),分裂后形成(),细胞分裂（）次，产生（）个子细胞,细胞分裂（）次，产生（）个子细胞,子细胞和母细胞的染色体数（）,子细胞染色体数

2、是母细胞的（）,不出现联会、四分体现象,减数I发生同源染色体的联会、四分体现象,细胞分裂过程中均出现（）和（），染色体复制（）次,体细胞,生殖细胞,1,2,2,4,相同,一半,染色体,纺锤体,1,1.interphase n.分裂间期,int(:)feiz,Interphase-The stage in the CELL CYCLE when the nucleus is not in a state of division.Interphase is divisible into various stages each characterized by a differing physiol

3、ogical activity.,间期：是细胞周期的一个时期，在这个时期里细胞核不分裂。根据细胞生理活性差异可以把间期分成不同的阶段。,Words and phrases,Cell cycle,Interphase 间期:G1+S+G2 M phase(mitosis 有丝分裂):,分裂间期,1、DNA复制2、中心粒复制,其中G1和G2期主要是合成有关蛋白质和RNA，S期则完成DNA 的复制。,2.prophase,prufeiz,n.分裂前期,3.metaphase n.分裂中期,metfeiz,4.anaphase nfeiz n.分裂后期,5.telophase,telfeiz,n.分裂

4、末期,有丝分裂前期,1）染色体出现2）每条染色体包含 兩条染色单体3）复制的中心粒 向两极移动4）纺锤体出现5）染色体中部和 纺锤丝相连6）核膜、核仁消失,prophase,prufeiz,n.分裂前期,The first stage of mitosis,during which individual chromosomes become visible.,有丝分裂中期,1）中心粒到达细胞两极2）染色体排列在细胞中央的赤道板上,赤道板（equatorial plane）,3.metaphase n.分裂中期,metfeiz,The second stage in mitosis,during

5、 which the chromosomes align at the equatorial plane.,1）着丝粒分裂，染色单体分离2）两条染色体受纺锤丝 牵引，向细胞两极移动,有丝分裂后期,4.anaphase nfeiz n.分裂后期,The third stage of mitosis,during which the centromeres split and the chromosomes move to the poles.,1）细胞质分裂2）赤道板附近的细胞膜凹陷3）细胞一分为二4）植物则是在细胞中 央形成细胞板，再 形成细胞壁,中央凹陷,5.telophase,telfei

6、z,n.分裂末期,有丝分裂末期,The last stage in mitosis,during which daughter nuclei are formed.,有丝分裂全过程,interphase,prophase,metaphase,anaphase,telophase,prometaphase,During mitosis,sister chromatids remain joined by their centromere until anaphase.,在有丝分裂期间，姐妹染色单体在分裂后期之前都是通过着丝点连接的。,For example：,A plant cell struc

7、ture that begins to form in the center of the cell and proceeds to the cell membrane,resulting in cytokinesis.,6.Cell plate,n.细胞板,The cell-plate membranes eventually form the two new plasma membranes of the daughter cells.,For example：,细胞板的膜最终形成两个新的子细胞的质膜。,7.centromere n.着丝粒;着丝点,sentr,mi,The small a

8、rea of a chromosome that does not stain with basic dyes(碱性燃料)during mitosis and meiosis;at interphase it is single while the rest of the chromosome is made up of two chromatids.,8.chalonen.抑素,klun,9.chromatidn.染色单体,krumtid,A replicated chromosome physically attached to an identical chromatid at cent

9、romere.,一对同源染色体（含4条染色单体）,一条染色单体,10.chromatinn.染色质,krumtin,Chromatin is the material that makes up chromosomes;it consists of DNA complexed with proteins.,由DNA和蛋白质组成的染色质，是构成染色体的原料。,11.cytokinesis n.胞质分裂,saitukaini:sis,Division（mitosis or meiosis)of the cytoplasm of one cell into two new cells.,12.dip

10、loidn.二倍体,diplid,Any nucleus,cell,or organism that posesses twice the haploid number of chromosomes.During the process of fertilization a zygote with the diploid set is produced.,通过受精作用使受精卵形成一个二倍体。,13.haploidn.单倍体,hplid,Genome-A complete haploid chromosome set.基因组：即一套完整的单倍体染色体。,Any nucleus,cell,or o

11、rganism that posesses twice a single set of unpaired chromosome.,14.histonen.组蛋白,histun,The small proteins have five families or classes:H1,H2A,H2B,H3,H4;and have a large positive charge(rich in Lys、Arg)which can bind very strongly to the negtively charged DNA in forming chromatin.,DNA和组蛋白组装成的结构叫做染色

12、体。,15.homologous pair humlgs pn.同源染色体对,一对同源染色体（含4条染色单体）,一条染色单体,16.karyotypen.核型，染色体组型,kritaip,The appearance of the chromosome complement of an organism or cell.核型：一个给定物种的染色体所表现出的物理学特征。,17.meiosisn.减数分裂,maiusis,The process by which a nucleus divides into four daughter nuclei,each containing half the

13、 number of chromosomes of the parent nucleus.,18.mitosis,mitusis,n.有丝分裂,间接核分裂,通过有丝分裂，每条染色体精确复制成的两条染色单体并均等地分到两个子细胞，使子细胞含有同母细胞相同的遗传信息。细胞有丝分裂过程，可以区分为：前期，中期，后期和末期。,有丝分裂和减数分裂的比较,比较,有丝分裂,减数分裂,不同点,相同点,分裂后形成(),分裂后形成(),细胞分裂（）次，产生（）个子细胞,细胞分裂（）次，产生（）个子细胞,子细胞和母细胞的染色体数（）,子细胞染色体数是母细胞的（）,不出现联会、四分体现象,减数I发生同源染色体的联会、

14、四分体现象,细胞分裂过程中均出现（）和（），染色体复制（）次,体细胞,生殖细胞,1,2,2,4,相同,一半,染色体,纺锤体,1,19.metaphase plate,n.中期板，赤道板,赤道板（equatorial plane）,20.nucleosome,nju:klisum,n.生化核小体,The basic unit of chromatin structurein eukaryotic cells.A nucleosome consists of 8 histone molecules,together with about 140 base pairs of DNA coiled a

15、round it.,Nucleosome is the basic unit of chromatin structure,21.spindle,spindl,n.纺锤体,An array of microtubule extending from pole tp pole and used in the movement of chromosomes.,Reviewing,1.anaphase n.分裂后期2.Cell plate n.细胞板3.centromere n.着丝粒4.chalone n.抑素5.chromatid n.染色单体6.chromatin n.染色质7.cytokin

16、esis n.胞质分裂8.diploid n.二倍体9.haploid n.单倍体10.histone n.组蛋白11.Homologous pair n.同源染色体对,nfez,sentrmi,kln;ke-,krmtd,krmtn,satokniss,12.interphase n.分裂间期 13.karyotype n.核型，染色体组型14.meiosis n.减数分裂15.Metaphase n.中期16.metaphase plate n.中期板，赤道板17.mitosis n.有丝分裂18.nucleosome n.核小体 19.prophase n.前期 20.spindle n

17、.纺锤体21.telophase n.末期,kr,tap,Pre-reading Activities:Listen to a video and think about the concept and mechanism of cell reproduction.Text analysis,Text Analysis,Text Analysis,1.The nucleus and chromosomes,The cell nucleus is the main repository of genetic information.Within the nucleus are the chrom

18、osomes-tightly coiled strands of DNA and clusters of associated proteins.,细胞核是遗传信息的主要贮存室。细胞核内部是染色体，包括紧密缠绕的线状DNA和与之相连的蛋白质串。,Long stretches of the continuous DNA molecule wind around these clusters of proteins,or histones,forming beadlike complexes known as nucleosomes.,长的伸展的持续的DNA分子围绕蛋白质串（组蛋白）缠绕，形成串珠

19、状的复合体，被称为核小体。,More coiling and supercoiling produces a dense chromosome structure.Each long strand of DNA combines with histones and nonhistone proteins to make up the substance chromatin.,更多的螺旋或超螺旋形成一个密集的染色体结构。每一个DNA长链与组蛋白或非组蛋白结合构成了染色质。,A pictorial display of an organisms chromosomes in the coiled,

20、condensed state is known as a karyotype.,有机体的染色体以螺旋的、浓缩的状态用图示的方式展示出来，称为染色体组型.,Karyotypes reveal that in most cells all but sex chromosomes are present as two copies,referred to as homologous pairs.,染色体组型显示出大多数细胞除了性染色体以外的其他染色体以2个拷贝的形式存在，被称为同源染色体对。,Non-sex chromosomes are called autosomes.Organisms wh

21、ose cells contain two sets of parental chromosomes are called diploid;those with cells containing a single set of parental chromosomes are called haploid.,非性染色体称为常染色体。细胞中含有两套亲本染色体的有机体称为二倍体；细胞中含有一套亲本染色体的有机体称为单倍体。,2 The cell cycle,The cell cycle is a regular sequence in which the cell grows,prepares f

22、or division,and divides to form two daughter cells,each of which then repeats the cycle.,细胞周期是一个有顺序的过程：细胞生长、准备分裂、分裂形成两个子细胞，每个子细胞再重新开始细胞周期。,Such cycling in effect makes single-celled organisms immortal.Many cells in multicellular organisms,including animal muscle and nerve cells,either slow the cycle

23、 or break out of it altogether.,这种有效的循环使得单细胞生物永生。多细胞生物的许多细胞包括动物肌肉和神经细胞能够使细胞周期时间延长或完全脱离细胞周期。,The normal cell cycle consists of four phases.The first three include G1,the period of normal metabolism;S phase,during which normal synthesis of biological molecules continues,DNA is replicated,and histones

24、are synthesized;,正常的细胞周期由四个阶段构成。前三个阶段包括G1，即正常的代谢的阶段；S期，期间持续进行生物分子的正常合成，即DNA复制和组蛋白的合成；,and G2,a brief period of metabolism and additional growth.Together the G1,S,and G2 phases are called interphase.,G2期（代谢和再次生长的短阶段）。G1、S和G2期合起来称为间期。,The fourth phase of the cell cycle is M phase,the period of mitosis

25、,during which the replicated chromosomes condense and move and the cell divides.,细胞周期的第四步为M 期（进行有丝分裂的阶段），在这一阶段，复制的染色体浓缩、运动，细胞分裂。,It is believed that properties of the cell cytoplasm control the cell cycle,along with external stimulators and inhibitors such as chalones.,被认为是细胞质的特性和外部的刺激因子和抑制剂例如抑素控制了细

26、胞周期。,3 Mitosis:Partitioning the hereditary material,Biologists divide the mitotic cycle into four phases.At the beginning of prophase the chromosomes each consist of two highly condensed chromatids attached to each other at a centromere.,生物学者把有丝分裂周期分为四步，分裂前期开始时，每一条染色体包括两条高度浓缩的染色单体，两者在着丝粒位置连在一起。,As p

27、rophase ends and metaphase begins,the condensed chromosomes become associated with the spindle.Eventually the chromosomes become arranged in a plane(called the metaphase plate)at a right angle to the spindle fibers.,当前期结束时，分裂中期开始。高度浓缩的染色体与纺锤体相连，最终染色体排在一个叫做中期板的平面上，与纺锤丝成垂直角度。,Next,during anaphase,the

28、two sister chromatids of each chromosomes split,and one from each pair drawn toward each pole of the cell.,接着，在分裂后期，每个染色体上的两个姊妹染色单体分开，每一对的一个分别移向细胞的一极。,During telophase nuclear envelopes begin to form around each set of chromosomes,and division of the cytoplasm takes place.,在分裂末期，围绕每一套染色体开始形成核膜，然后开始细

29、胞质的分裂。,As mitosis proceeds,the spindle microtubules play a crucial role in ensuring that both paired and separated chromatids move in the right directions at the proper times.,当有丝分裂进行时，纺锤体的微管在保证成对的和分离的染色单体适时向正确的方向运动起到关键作用。,Each half of the spindle forms as microtubules extend from each pole of a div

30、iding cell to the region of the metaphase plate.,当微管从每个分裂细胞的两极延伸至赤道板时，形成了纺锤体的每一半。,During prophase,other microtubules,the centromeric fibers,extend outward from the spindle poles to structures on the chromosomes called kinetochores.During anaphase the fibers begin to shorten,and the chromatids begin

31、to move apart.,在有丝分裂前期，另外一种微管，着丝粒纤维从纺锤体的两极向外延伸到染色体上叫做动粒的结构上。在分裂后期，纤维开始缩短，染色单体开始分开。,knitk;ka-,kinetochore,动粒,The spindle forms differently in plant and animal cells.In animals it is associated with centriole,while in plant and fungal cells spindle formation is associated with regions called microtubu

32、le organizing centers.,在植物和动物细胞中纺锤体的形成不同，动物细胞中，与中心体有关。在植物和真菌细胞中纺锤体的形成与叫做微管组织中心的区域有关。,4 Cytokinesis:Partitioning the cytoplasm,The division of the cell cytoplasm at the end of mitosis is called cytokinesis.In animal cells it takes place as a ring of actin filaments contracts around the cell equator,p

33、inching the cell in two.,有丝分裂结束时细胞质的分裂称为胞质分裂。动物细胞中胞质分裂过程中，首先肌动蛋白形成的环在细胞赤道周围进行收缩，将细胞收缩为两部分。,In plant cells,which are bounded by a cell wall,cytokinesis involves the building of a new cell plate across the dividing cell at its equator.Cell wall material is then deposited in the region of the cell plat

34、e.,植物细胞有细胞壁包被，胞质分裂包括围绕新细胞的赤道周围形成新细胞板，然后细胞壁物质在细胞板位置沉积。,5 Meiosis:The basis of sexual reproduction,Meiosis is a special form of cell division that takes place in the reproductive organs that produce sex cells.,减数分裂是细胞分裂的特殊形式，在产生生殖细胞的生殖器官中发生。,Like mitosis,it takes place after DNA replication has occurr

35、ed and involves two sequential nuclear divisions(meiosis I and meiosis II).These divisions result in four daughter cells,each with half the number of chromosomes of the parent cell.,如有丝分裂，它发生于DNA 复制后，包括两个有顺序的核分裂阶段（减数分裂I期和减数分裂II期）。这些分裂产生4个子细胞，每一个子细胞的染色体数是母细胞染色体数的一半。,The phenomenon of crossing over du

36、ring meiosis results in exchanges of genetic information between chromosomes.Hence,the homologous chromosomes distributed to different progeny cells are not identical.,减数分裂交叉现象的出现导致了染色体之间互换遗传信息。这样分配到不同后代细胞中的同源的染色体并不相同。,As in mitosis two chromatids exist for each chromosome at the beginning of propha

37、se I.,象有丝分裂那样，在分裂前I期的开始，每个染色体含有两条染色单体。,During this phase the homologous chromosomes undergo synapsis or pairing,which is brought about by a bridging structure of proteins and RNA called the synaptinemal complex.,在这一阶段，同源的染色体经历了联会或配对，这是由蛋白质和RNA形成的桥状结构-联会复合体的出现而发生的。,snpss,synapsis,联会,The homologous pa

38、irs stay together when they align on the metaphase plate.,当同源染色体对排列于赤道板上时，（这两条染色体）同时存在。,Unlike the anaphase of mitosis,however,during anaphase I the two chromatids of each chromosome stay joined at the centromere and move together to one of the two poles of the cell.,然而，与有丝分裂后期不同的是，减数分裂后期I每个染色体的两条染色

39、单体在着丝粒处相连，一起移向细胞的一极。,It is this event that results in the halving of the chromosome number in the four daughter cells that result from meiosis.,正是由于这一事件导致减数分裂中4个子细胞的染色体数目减半。,During telophase I nuclear envelopes enclose the chromosomes in nuclei,and in most species cytokinesis(the first nuclear divis

40、ion)follows.,在减数分裂末期I，核被膜将染色体包裹在细胞核中，接着多数种类开始胞质分裂（第一次细胞核分裂）。,The second nuclear division begins with metaphase II,in which the chromosomes in each daughter cell again align on a metaphase plate.,第二次细胞核分裂开始于减数分裂中期II，每个子细胞中的染色体重新排列于中期板上。,The cenromeres finally divide,and each sister chromatid moves to

41、 one of the poles of the spindle.The next phase is telophase II,followed again by cytokinesis.The result of the entire process is four haploid cells in which parental chromosomes are randomly distributed.,着丝粒最终分裂，每个姊妹染色单体移向纺锤体的一极。下一个阶段是减数分裂末期II，然后是胞质分裂。整个过程的结果是4 个单倍体细胞，亲本的染色体被随机分配。,6)Asexual versus

42、sexual reproduction,Mitosis and meiosis,respectively,make simple cell division and sexual reproduction possible.Each means of passing on hereditary information has advantages.,有丝分类和减数分裂分别使简单的细胞分裂和有性生殖成为可能。每一种传递遗传信息的方式都有优点。,In asexual reproduction the parent organism gives rise to offspring that are

43、genetic clones of the parent.,无性生殖产生后代时克隆（完全复制）了中亲本的遗传信息。,The advantages of this type of reproduction are that it preserves the parents successful genetic complement,requires little or no specialization of reproductive organs,and is more rapid than sexual reproduction.,这种生殖类型的优点是它保存了亲本成功的遗传信息，基本或完全不

44、需要特化出生殖器官，与有性生殖相比更迅速。,A major disadvantage of the asexual mode is that a single catastrophic event or disease may destroy an entire population of genetically identical organisms.,无性类型的主要缺点是单一的灾难性事件或疾病就可以摧毁遗传信息完全相同的整个种群。,A prime benefit of sexual reproduction is that it provides genetic variability a

45、nd a ready mechanism for the elimination of deleterious mutations.It also allows“new”gene forms to arise and spread through populations.,有性生殖的主要好处是它能够提供遗传的多样性，具有迅速的清除有害变异的机制。它也使新基因形式出现、增加并扩展到整个种群。,Review the former content：,1.anaphase n.分裂后期2.Cell plate n.细胞板3.centromere n.着丝粒;着丝点4.chalone n.抑素5.chr

46、omatid n.染色单体6.chromatin n.染色质7.cytokinesis n.胞质分裂8.diploid n.二倍体9.haploid n.单倍体10.histone n.组蛋白11.Homologous pair n.同源染色体对,12.interphase n.分裂间期 13.karyotype n.核型，染色体组型14.meiosis n.减数分裂15.Metaphase n.中期16.metaphase plate n.中期板，赤道板17.mitosis n.有丝分裂18.nucleosome n.生化核小体 19.prophase n.前期 20.spindle n.纺

47、锤体21.telophase n.末期,Exercises,I Key terms:matching,Match each term on the left with the most appropriate description on the right,a.DNA+histoneb.two setsc.X and Yd.one sete.chromosome displayf.set of microtublesg.plant divisionh.gamete productioni.sequence of cell growth and divisionj.cell divisionk

48、.crossing overl.inhibit cell divisionm.Division of cytoplasmn.single chromosome copyo.positively charged protein,1.cytokinesis2.synapsis3.histone4.mitosis5.cell cycle6.chalone7.spindle8.chromatid9.nucleosome10.diploid 11.meiosis12.cell plate13.sex chromosome14.karyotype15.haploid,I Key terms:matchin

49、g,II.True or false,Autosomes include X and Y chromosomes.2.Cells enter G2 at the end of the S phase.3.Chalones promote cell division.4.The nuclear envelope forms in telophase.5.Plant cells have the most prominent centrioles.6.Nuclear division may occur without cytokinesis.7.Homologous chromosomes pa

50、ir in synapsis.8.Chromosomes break at chiasmata(交叉).9.Sexual organisms cannot be cloned.10.All daughter cells are hapoid.,kazmt,III Completion,If human chromsomes are stained on a slide,the resulting display,which is called a karyotype,should contain twenty-two pairs of autosomes and one pair of sex