生物专业英语第三章有丝分裂

1、1,Unit Three,Cellular Reproduction: Mitosis and Meiosis 细胞的增殖：有丝分裂和减数分裂,He Chengguang,2,细胞分裂(cell division)是一切生物生长、发育、繁殖的基础. 三种方式: 无丝分裂amitosis:比较低等，不常见. 有丝分裂Mitosis:大多数动植物的体细胞的形成方式，它能保证亲代与子代之间的连续性以及遗传物质的稳定性. 减数分裂meiosis 范围是进行有性生殖的生物；时期是从原始生殖细胞发展到成熟生殖细胞.,3,无丝分裂是正常细胞的增殖方式之一,主要见于高度分化的细胞,如肝细胞、肾小管上皮细胞、肾

2、上腺皮质细胞等。 这种分裂方式常出现于高度分化成熟的组织中， 如蛙的红细胞的分裂，在某些植物的胚乳中胚乳细胞的分裂等。,Amitosis,4,Mitosis,有丝分裂(Mitosis),W. Fleming （1882年）首次发现于动物及E. Strasburger（1880）年发现于植物 特点是有纺锤体spindle、染色体chromosome出现，子染色体被平均分配到子细胞，是真核细胞分裂产生体细胞的过程; 这种分裂方式普遍见于动物和高等植物. 通过有丝分裂，作为遗传物质的(DNA)得以准确地在细胞世代间相传，实现组织发生和个体发育 肿瘤发生-致癌因子使有丝分裂的调控失常导致,5,参与有丝

3、分裂的细胞器,中心体centriole与纺锤体的形成有关； 线粒体mitochondria与提供能量有关 ； 高尔基体golgi body 与植物新形成的细胞壁有关 核糖体ribosome与间期进行的DNA复制需要的 蛋白质有关,动植物的不同 动物细胞有中心体，在细胞分裂的间期，中心体的两个中心粒各自产生了一个新的中心粒，细胞中有两组中心粒. 动物细胞在有丝分裂间期中心体复制，植物细胞中心体则没有复制.,6,Mitosis,cell cycle,从一次分裂完成时开始，到下一次分裂完成时为止， 为一个细胞周期.,7,Mitosis 有丝分裂,8,减数分裂（Meiosis）是有性生殖的个体在形成生

4、殖细胞过程中发生的一种特殊分裂方式 在减数分裂过程中，减数分裂过程中染色体仅复制一次，细胞连续分裂两次，减数分裂的结果是，两次分裂中将同源染色体与姐妹染色单体均分给子细胞，使最终形成的配子中染色体仅为性母细胞的一半。受精时雌雄配子结合，恢复亲代染色体数，从而保持物种染色体数的恒定。 成熟生殖细胞中的染色体数目比原始生殖细胞的减少一半。 不仅保证物种染色体数目稳定的机制，且是物种适应环境变化不断进化的机制。,范围是进行有性生殖的生物； 时期是从原始生殖细胞发展到成熟生殖细胞,Meiosis,9,10,Meiosis maiusis 减数分裂,11,12,Metaphase plate 赤道板，中

5、期板,13,Cell plate 细胞板,14,Chromatid 染色单体,Centromere sentrm着丝粒 染色体上一段非编码的DNA, 对动粒（或动粒蛋白）有组织和整合作用,15,Chalone klun 抑素 成熟的和分化的细胞产生的蛋白质，抑制DNA合成、原始细胞分裂，具有组织特异性，但无种属特异性。,16,Nucleosome nju:klisum 核小体,DNA和组蛋白(histone）,H1（H5）、H2A、H2B、H3和H4,17,Histone 组蛋白 五种类型：H1、H2A、H2B、H3、H4,18,Chromatin krumtin 染色质,core parti

6、cle 核心颗粒 dinucleosome model 双核小体模型 chromatin fiber model 染色质纤维模型,19,Cytokinesis saitukaini:sis 胞质分裂,20,Diploid diplid 二倍体，双倍的 Bi, di, dipl, twi, du /前缀/ 二，双，两 Haploid hplid 单倍体 Hapl(o)-, mono-, uni- /前缀/ 单，一，独 Monoxide mnksad 一氧化物 unicellular ju:niseljul adj. 单细胞的,21,Homologous pair 同源染色体对,22,Karyot

7、ype kritaip 核型，染色体组型,23,Interphase int(:)feiz 分裂间期,24,Prophase prfez 分裂前期,Spindle 纺锤体,25,Metaphase metfeiz 分裂中期,26,Anaphase nfeiz 分裂后期,Pole n.棒, 柱, 杆, 竿, 极, 磁极, 电极;vt.用竿支撑, 用棒推;vi.撑篙,27,Telophase telfeiz 分裂末期,29,Autosome :tsum n.正染色体, 常染色体 Kinetochore kini:tk: n.生动粒；着丝粒 Partition p:tin n.分割, 划分, 瓜分,

8、 分开, 隔离物;vt.区分, 隔开, 分割Pinch n.捏,撮,收缩,紧急关头,匮乏, 压力 vt. 掐,夹痛, 修剪, 勒索, 使感缺乏, 使萎缩, 偷 vi.收缩, 节省 Progeny prdni: n.后裔,后代 a-,an- (元音前用) 无，非 asexualeiseksjul 无性繁殖的; abacterial 非细菌性的; amoral em:rl无道德感的,30,1. The nucleus and chromosomes,31,The cell nucleus is the main repository of genetic information.Within th

9、e nucleus are the chromosomestightly coiled strands of DNA and clusters of associated proteins.Long stretches of the continuous DNA molecule wind around these clusters of proteins, or histones, forming beadlike complexes known as nucleosomes. 细胞核是贮藏遗传信息的主要场所。细胞核里的是染色体紧密盘绕成螺旋的DNA链和相关的成簇蛋白质。延伸长链DNA分子缠

10、绕着成簇的蛋白质，或组蛋白，形成珠链状的核小体。,32,More coiling and supercoiling produces a dense chromosome structure. Each long strand of DNA combine with histones and nonhistone proteins to make up the substance chromatin. 这些染色质进一步螺旋和超螺旋形成致密的染色体结构。每个长链DNA与组蛋白和非组蛋白一起构成染色质。,33,A pictorial display of an organisms chromoso

11、mes in the coiled, condensed state is known as a karyotype. Karyotype reveal that in most cells all but sex chromosomes are present as two copies, referred to as homologous pairs. Non-sex chromosomes are called autosomes. 对生物这种致密的、双螺旋状态的图示我们称为染色体组。通过染色体组，我们发现除了性染色体外，大多数细胞的染色体成对出现，称同源染色体对。非性染色体称常染色体。

12、,34,Organisms whose cells contain two sets of parental chromosomes are called diploid; those with cells containing a single set of parental chromosomes are called haploid. 生物体内的细胞含有两套父母本染色体的称二倍体；含有单套染色体的称单倍体。 多倍体：带有两套以上同源染色体的细胞或个体。,35,2 The cell cycle,36,regular 有规律的 divide 划分 分离 repeat vt. 重复 in ef

13、fect 实际上 single-celled 单细胞的 immortal im:tl adj. 不死的；永恒的 multicellular mltiseljul多细胞的 muscle msl n. 肌肉 nerve n:v n. 神经 altogether 完全地 division 分开,37,The cell cycle is a regular sequence in which the cell grows, prepares for division, and divides to form two daughter cells, each of which then repeats

14、the cycle. Such cycling in effect makes single-celled organisms immortal. Many cells in multicellular organisms, including animal muscle and nerve cells, either slow the cycle or break out of it altogether. 在细胞生长过程中，细胞循环遵循固定程序，首先进行分裂准备，分裂成2个子细胞，子细胞再循环。此循环的存在让单细胞生物得以“长生不死”。多细胞生物中的许多细胞，包括动物肌细胞和神经细胞，要么

15、细胞循环速度降低，要么全部从这个循环中脱离。,38,The normal cell cycle consists of four phases. The first three include G1, the period pirid of normal metabolism; S phase, during which normal synthesis of biological molecules continues, DNA is replicated, and histones are synthesized; and G2, a brief period of metabolism

16、and additional growth. Together the G1, S, and G2 phases are called interphase. 正常的细胞循环由4个阶段组成。头三个阶段包括G1, 正常新陈代谢；S期, 生物分子正常合成同时，复制DNA，合成组蛋白； G2 期，短期的新陈代谢和继续生长。G1, S, 和G2称分裂间期。,39,The fourth phase of the cell cycle is M phase, the period of mitosis, during which the replicated chromosomes condense an

17、d move and the cell divides. It is believed that properties of the cell cytoplasm control the cell cycle, along with externalekst:nl stimulators and inhibitors such as chalones. 最后是M期有丝分裂期。此期间，复制的染色体浓缩、移动然后细胞分裂。现在普遍接受的是染色质的特征，以及外部刺激物、抑制因子如抑素等控制了细胞循环。,40,3 Mitosis: partitioning the hereditary materia

18、l p:tini n.分割 hireditri adj. 遗传的,41,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. As prophase ends and metaphase begins, the condensed chromosomes become assoc

19、iated with the spindle. 生物学家将有丝分裂划分为4个阶段。分裂前期，高度浓缩的两个染色单体通过着丝粒连接在一起。在分裂前期后期和分裂中期前期，浓缩的染色体与纺锤体相连。 Eventually the chromosomes become arranged in a plane (called the metaphase plate) at a right angle to the spindle fibers. 最后染色体与纺锤丝垂直的角度排列在赤道板上。,42,Next, during anaphase, the two sister chromatids of ea

20、ch chromosome split, and one from each pair is drawn toward each pole of the cell. During telophase nuclear envelopesenvlups begin to form around each set of chromosomes, and division of the cytoplasm takes place. 在分裂后期，两个姊妹单体分离，分别被拽向细胞两极。在分裂末期，在每套染色体周围形成核膜，然后细胞质分裂。,43,As mitosis proceeds, the spind

21、le microtubules play a crucial role in ensuring that both paired and separated chromatids move in the right directions at the proper times. Each half of the spindle forms as microtubules extend from each pole of a dividing cell to the region of the metaphase plate. During prophase, other microtubule

22、s, 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 to move apart. 在有丝分裂过程中，纺锤体微管在确保染色体对和染色单体在适当时间向正确方向分离时起着关键作用。纺锤体微管由两极向赤道板延伸。在分裂前期，其它微管，着丝粒纤维由纺锤体的两极延伸到染色体的动粒。在分

23、裂后期，纤维开始变短，染色单体分离。,44,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 microtubule organizing centers. 植物和动物细胞纺锤体的形成不同。动物细胞中，纺锤体与中心粒相连；而在植物和真菌细胞中，纺锤体与微管组织中心相连。,45,4

24、 Cytokinesis: partitioning the cytoplasm,卵裂沟,46,centriole sentriuln. 细胞中心粒，中心体 fungal fladj. 真菌的 fungus 真菌 cleavage furrow kli:vd f:r 卵裂沟 contracting ring of microfilament微丝收缩环,47,cytokinesissaitukaini:sis 胞质分裂 actin filaments 肌动纤维丝 equator ikweit n. 赤道 pinch pint vt. 捏，掐；挤痛，夹痛 Cell wall 细胞壁 deposit

25、e 沉积 cell plate 细胞板,48,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, pinching the cell in two. In plant cells, which are bounded by a cell wall, cytokinesis involves the b

26、uilding of a new cell plate across the dividing cell at its equator. Cell wall material is then depositeddipzitid in the region of the cell plate. 在动物细胞中，环形肌动蛋白丝延赤道板收缩而使细胞一分为二。在细胞壁包围的植物细胞中，胞质分离需要在细胞中央形成新的细胞板。 细胞壁成份随后在此区域沉积。,49,5 Meiosis: the basis of sexual reproduction,synapsis sinpsis 生染色体结合; 联会 s

27、exual reproduction seksjul ri:prdkn 有性生殖 mitotic spindlemittik 有丝分裂纺锤丝,50,meiosis,Fig. meiosis in a plant pollen grain. 花粉粒 pln,51,reproductive organs ri:prdktv 生殖器官 sequential skwenl 有序的 nuclear divisions 核分裂 meiosis I and meiosis 减数第一次分裂和第二次分裂,52,Meiosis is a special form of cell division that tak

28、es place in the reproductive organs that produce sex cells. Like mitosis, it takes place after DNA replication has occurred and involves two sequential nuclear divisions (meiosis I and meiosis ). These divisions result in four daughter cells, each with half the number of chromosomes of the parent ce

29、ll. 减数分裂是细胞分裂的特殊形式，发生在产生性细胞的性器官中。跟有丝分裂相似，它也是发生在DNA复制后，但有连续的两个核分裂。分裂的结果产生4个子细胞，分别含有亲本一半的染色体数。,53,phenomenon finminn 现象 crossing overkrsi uv 交换，互换 exchangeiksteind 交换 homologous chromosomes 同源染色体 progeny prdni: 子代 后裔 identicalaidentikl adj. 同一的；完全同样的,54,The phenomenon of crossing over during meiosis r

30、esults in exchanges of genetic information between chromosomes. Hence, the homologous chromosomes distributed to different progeny cells are not identical. 有丝分裂过程中的交换现象的结果是染色体间的遗传信息交换。因此，同源染色体是分配到哪个子细胞并不确定。,55,undergo ndu 经历，遭受 synapsis sinpsis 联会 pairing 配对 bridging 桥接 synaptonemal complex 联会复合体 al

31、ign lan vi. 排列；成一条线 halving h:vi n. 对分，二等分，减半 result from 产生于 由.引起,56,As in mitosis two chromatids exist for each chromosome at the beginning of prophase 1. During this phase the homologous chromosomes undergo synapsis, or pairing, which is brought about by a bridging structure of proteins and RNA c

32、alled the synaptonemal complex. The homologous pairs stay together when they align on the metaphase plate. 跟在有丝分裂中一样，在分裂前期每条染色体存在两个同源染色单体。在此阶段，同源染色体经历联会（或配对）。期间通过蛋白质和RNA组成的连接结构联会复合体。,57,Unlike the anaphase of mitosis, however, during anaphase I the two chromatids of each chromosome stay joined at th

33、e centromere and move together to one of the two poles of the cell. It is this event that results in the halving of the chromosome number in the four daughter cells that result from meiosis. 与有丝分裂不同的是，每组染色体的两个染色单体连接在着丝点上并一起移向细胞两极的一级。由此而导致4个子细胞染色体数减半。,58,enclose inkluz 把围起来 nucleus 细胞核 复数 nuclei nucl

34、ear 细胞核的 randomly rndmli 随机地 metaphase plate 中期板 distribute distribju:t vt. 分配,59,During telophase I nuclear envelopes enclose the chromosomes in nuclei, and in most species cytokinesis (the first nuclear division) follows. The second nuclear division begins with metaphase , in which the chromosomes

35、 in each daughter cell again align on a metaphase plate. The centromeres finally divide, and each sister chromatid moves to one of the poles of the spindle. The next phase is telophase , followed again by cytokinesis. The result of the entire process is four haploid cells in which parental chromosom

36、es are randomly distributed. 第二次核分裂开始于分裂中期，子细胞中染色体重新排列在赤道板上。着丝粒最终分离，每个姊妹染色单体分向两极。接着胞质分裂。产生4个单倍体，父母染色体随机分配。,60,Asexual eiseksjul adj. 无性的；无性生殖的 versus v:ss 与.比较 Gametesmi:ts 配子,61,6 Asexual versus sexual reproduction 无性繁殖与有性生殖的比较,Asexual reproduction NO exchange of genetic material Mitosis Sexual rep

37、roduction Exchange of genetic material Meiosis Gametes,62,respectively rispektivli adv. 各自地；分别地 pass on 传递 hereditary information hireditri 遗传信息 asexual reproduction 无性繁殖 sexual reproduction 有性繁殖 give rise to 生产 offspring fspri 子代 genetic clones 基因克隆 同样的基因 preserve priz:v 保持 genetic complement kmplimnt 基因互补 specialization spelazen 特殊化,63,Mitosis and meiosis, respectively, make simple cell division and sexual re