大学生物专业英语lessonthree.pptx

大学生物专业英语lesson_threerepository n.贮藏室贮藏室,智囊团智囊团,知识库知识库,仓库仓库chromosome n.生物生物染色体染色体histone n.生化生化组蛋白组蛋白nucleosome n.生化生化核小体核小体chromatin n.核染质核染质,染色质染色质pictorial adj.图示的图示的 n.画报画报karyotype n.生物生物 染色体组型染色体组型homologous pair 同源染色体对同源染色体对autosome n.正染色体正染色体,常染色体常染色体6/1/2024diploid adj.双重的双重的,n.二倍体二倍体haploid n.生物生物单倍体单倍体 adj.单一的单一的immortal adj.不朽的不朽的Chalone n.生化生化抑素抑素prophase n.(细胞分裂细胞分裂)前期前期chromatid n.生物生物染色单体染色单体centromere n.生生着丝点着丝点,着丝粒着丝粒metaphase n.中期中期anaphase n.生生(细胞分裂的细胞分裂的)后期后期6/1/2024Telophase n.生生(细胞有丝分裂的细胞有丝分裂的)末期末期kinetochore n.生生动粒动粒,着丝粒着丝粒,着丝点着丝点cytokinesis n.细胞浆移动细胞浆移动,原浆移动原浆移动pinching v.收聚收聚cell plate 细胞板细胞板mitosis n.有丝分裂有丝分裂meiosis n.减数分裂减数分裂,成熟分裂成熟分裂6/1/2024Halving 对分对分,二等分二等分,减半减半Synapsis 联会联会synaptinemal complex 联会复合物联会复合物Asexual adj.无性的无性的,无性生殖的无性生殖的catastrophic adj.悲惨的悲惨的,灾难的灾难的Elimination n.排除排除,除去除去,消除消除,消灭消灭6/1/20241.The nucleus and chromosomes6/1/2024The cell nucleus is the main repository of genetic information.细胞核是贮藏遗传信息的主要场所。细胞核是贮藏遗传信息的主要场所。Within the nucleus are the chromosomestightly coiled strands of DNA and clusters of associated proteins.细胞核里的是染色体紧密盘绕成螺旋的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。链和相关的成簇蛋白质。6/1/2024 Long stretches of the continuous DNA molecule wind around these clusters of proteins,or histones,forming beadlike complexes known as nucleosomes.长链长链DNA分子缠绕着成簇的蛋白质，或组蛋白，形成珠链状的核小体。分子缠绕着成簇的蛋白质，或组蛋白，形成珠链状的核小体。6/1/2024More coiling and supercoiling produces a dense chromosome structure.进一步的螺旋和超螺旋形成致密的染色体组结构。进一步的螺旋和超螺旋形成致密的染色体组结构。Each long strand of DNA combine with histones and nonhistone proteins to make up the substance chromatin.每个长链每个长链DNA与组蛋白和非组蛋白一起构成染色质物质。与组蛋白和非组蛋白一起构成染色质物质。6/1/2024A pictorial display of an organisms chromosomes in the coiled,condensed state is known as a karyotype.生物体中的致密的超螺旋状态的染色体的表型称为核型生物体中的致密的超螺旋状态的染色体的表型称为核型Karyotype reveal that in most cells all but sex chromosomes are present as two copies,referred to as homologous pairs.表型显示：在大多数细胞里，除了性染色体外，其它的染色体都是成对出现的，称之为同源染色体对。表型显示：在大多数细胞里，除了性染色体外，其它的染色体都是成对出现的，称之为同源染色体对。6/1/2024Non-sex chromosomes are called autosomes.非性染色体称常染色体。非性染色体称常染色体。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.细胞里含有两套亲本染色体的生物体称二倍体；细胞里含有单套染色体的生物体称单倍体。细胞里含有两套亲本染色体的生物体称二倍体；细胞里含有单套染色体的生物体称单倍体。6/1/20246/1/20242.The cell cycle细胞周期细胞周期6/1/2024The 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 the cycle.细胞周期遵循特定的程序：细胞生长，分裂准备，分裂成细胞周期遵循特定的程序：细胞生长，分裂准备，分裂成2个子细胞，每个子细胞再循环。个子细胞，每个子细胞再循环。Such cycling in effect makes single-celled organisms immortal.此循环可以有效的使得单细胞生物永生。此循环可以有效的使得单细胞生物永生。6/1/2024Many cells in multicellular organisms,including animal muscle and nerve cells,either slow the cycle or break out of it altogether.多细胞生物中的许多细胞，包括动物肌肉和神经细胞，要么减慢周期速度，要么一起脱离细胞周期。多细胞生物中的许多细胞，包括动物肌肉和神经细胞，要么减慢周期速度，要么一起脱离细胞周期。The normal cell cycle consists of four phases.正常细胞周期由正常细胞周期由4个时期组成。个时期组成。6/1/2024The first three include G1,the period 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 and additional growth.前前三三个个时时期期包包括括G1,正正常常新新陈陈代代谢谢时时期期；S期期,生生物物分分子子的的合合成成继继续续，同同时时，DNA复复制制，组组蛋蛋白白合合成成；G2 期期，新陈代谢和进一步生长的短暂时期。新陈代谢和进一步生长的短暂时期。Together the G1,S,and G2 phases are called interphase.G1,S,和和G2一起称为分裂间期。一起称为分裂间期。6/1/2024The fourth phase of the cell cycle is M phase,the period of mitosis,during which the replicated chromosomes condense and move and the cell divides.细胞周期的第四个时期是细胞周期的第四个时期是M期，有丝分裂期，复制的染色体浓缩，移动并细胞分裂。期，有丝分裂期，复制的染色体浓缩，移动并细胞分裂。6/1/2024It is believed that properties of the cell cytoplasm control the cell cycle,along with external stimulators and inhibitors such as chalones.据称是细胞质中的物质与外来的激活因子和抑制因子如据称是细胞质中的物质与外来的激活因子和抑制因子如抑素等一起控制了细胞周期。抑素等一起控制了细胞周期。6/1/20243.Mitosis:partitioning the hereditary material有丝分裂：有丝分裂：遗传物质的分离遗传物质的分离6/1/2024Biologists divide the mitotic cycle into four phases.生物学家将有丝分裂划分为生物学家将有丝分裂划分为4个阶段。个阶段。At the beginning of prophase the chromosomes each consist of two highly condensed chromatids attached to each other at a centromere.分分裂裂前前期期，每每个个染染色色体体是是由由高高度度浓浓缩缩的的通通过过着着丝丝粒粒连连接接在在一一起起的的两两个个染染色色单单体体组组成成。(分分裂裂前前期期，高高度度浓浓缩缩的的两两个个染染色单体通过着丝粒连接在一起形成染色体色单体通过着丝粒连接在一起形成染色体)6/1/2024As prophase ends and metaphase begins,the condensed chromosomes become associated with the spindle.分分裂裂前前期期结结束束，紧紧接接着着是是分分裂裂中中期期，浓浓缩缩的的染染色色体体与与纺纺锤锤体体相相连连。(在在分分裂裂前前期期后后期期和和分分裂裂中中期期前前期期，浓浓缩缩的的染染色色体体与纺锤体相连与纺锤体相连)Eventually the chromosomes become arranged in a plane(called the metaphase plate)at a right angle to the spindle fiber.最后染色体在纺锤丝的牵引下以正确的角度排列在赤道板上。最后染色体在纺锤丝的牵引下以正确的角度排列在赤道板上。6/1/2024Next,during anaphase,the two sister chromatids of each chromosome split,and one from each pair is drawn toward each pole of the cell.在分裂后期，两个姊妹染色单体分离，分别被拉向细胞两极。在分裂后期，两个姊妹染色单体分离，分别被拉向细胞两极。During telophase nuclear envelope begin to form around each set of chromosomes,and division of the cytoplasm takes place.在分裂末期，在每套染色体周围形成核膜，细胞质分裂发生。在分裂末期，在每套染色体周围形成核膜，细胞质分裂发生。6/1/2024As 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.在有丝分裂过程中，纺锤体微管在确保染色单体配对和在适当时间以正确方向进行分离中发挥了关键性的作用。在有丝分裂过程中，纺锤体微管在确保染色单体配对和在适当时间以正确方向进行分离中发挥了关键性的作用。Each half of the spindle forms as microtubules extend from each pole of a dividing cell to the region of the metaphase plate.微管从正在分裂的细胞两极向赤道板延伸，就形成了纺锤体的一半。微管从正在分裂的细胞两极向赤道板延伸，就形成了纺锤体的一半。6/1/2024 During prophase,other microtubules,the centromeric fiber,extend outward from the spindle poles to structures on the chromosomes called kinetochores.在分裂前期，其它微管，着丝粒纤维从纺锤体的两极延伸到染色体的动粒区域。在分裂前期，其它微管，着丝粒纤维从纺锤体的两极延伸到染色体的动粒区域。During anaphase the fibers begin to shorten,and the chromatids begin to move apart.在分裂后期，纤维开始变短，染色单体分离。在分裂后期，纤维开始变短，染色单体分离。6/1/2024Mitosis:prophasemetaphaseanaphasetelophasechromosome condensationmitotic spindle assemblynuclearenvelopebreakdownchromosomes alignin the central planesister chromatids split and are drawn by the spindle towardsthe polesProphaseSister chromatidsPrometaphaseMetaphaseAnaphaseCytokinesisTelophaseInterphaseCentrosomeMicrotubulespindle microtubulesattach to kinetochorenuclear envelopereforms6/1/2024着丝粒（着丝粒（centromere）：位于染色体缢缩部）：位于染色体缢缩部位，是异染色质，是在染色体最后复制的部位。位，是异染色质，是在染色体最后复制的部位。着丝粒在染色体上的位置是确定的。着丝粒在染色体上的位置是确定的。动粒（动粒（kinetochore）：位于着丝粒外侧的蛋）：位于着丝粒外侧的蛋白质复合体。白质复合体。6/1/20246/1/2024The spindle forms differently in plant and animal cells.植物和动物细胞中的纺锤体的形成是不同的。植物和动物细胞中的纺锤体的形成是不同的。In animal it is associated with centriole,while in plant and fungal cells spindle formation is associated with regions called microtubule organizing centers.在动物中，纺锤体的形成与中心粒相关，而在植物和真菌细胞中，纺锤体的形成与微管组织中心相关。在动物中，纺锤体的形成与中心粒相关，而在植物和真菌细胞中，纺锤体的形成与微管组织中心相关。6/1/20244.Cytokinesis:Partitioning the cytoplasm胞质分裂：细胞质分离胞质分裂：细胞质分离6/1/2024The division of the cell cytoplasm at the end of mitosis is called cytokinesis.在有丝分裂结束时，细胞质的分裂称为胞质分裂。在有丝分裂结束时，细胞质的分裂称为胞质分裂。In animal cells it takes place as a ring of actin filaments contracts around the cell equator,pinching the cell in two.在动物细胞中，环形的肌动蛋白纤维围绕赤道板收缩，将细胞一分为二。在动物细胞中，环形的肌动蛋白纤维围绕赤道板收缩，将细胞一分为二。6/1/2024In 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.在在植植物物细细胞胞中中，被被细细胞胞壁壁包包围围，胞胞质质分分裂裂涉涉及及到到在在正正在在分分裂裂的的细细胞胞的的赤赤道道板板上上新新的的细细胞胞板板的的形形成成。(在在植植物物细细胞胞中，在赤道板形成新的细胞板。中，在赤道板形成新的细胞板。)Cell wall material is then deposited in the region of the cell plate.然后，细胞壁材料在细胞板区域沉积然后，细胞壁材料在细胞板区域沉积6/1/2024Actin and MyosinActin and MyosinActin and MyosinActin and Myosinand Cytokinesisand Cytokinesisand Cytokinesisand CytokinesisOperation of the Contractile Ringduring Cytokinesis6/1/2024 5.Meiosis:the basis of sexual reproduction减数分裂：有性生殖的基础减数分裂：有性生殖的基础6/1/2024Meiosis is a special form of cell division that takes place in the reproductive organs that produce sex cells.减数分裂是发生在产生性细胞的生殖器官中的一种特殊的分裂形式。减数分裂是发生在产生性细胞的生殖器官中的一种特殊的分裂形式。(减数分裂是性细胞分裂的特殊形式。减数分裂是性细胞分裂的特殊形式。)Like mitosis,it takes place after DNA replication has occurred and involves two sequential nuclear divisions(meiosis I and meiosis II).如有丝分裂，它也是发生在如有丝分裂，它也是发生在DNA复制后，并有两个连续的核分裂。复制后，并有两个连续的核分裂。6/1/2024These division results in four daughter cells,each with half the number of chromosomes of the parent cell.减数分裂产生减数分裂产生4个子细胞，分别含有亲本一半的染色体数。个子细胞，分别含有亲本一半的染色体数。The phenomenon of crossing over during meiosis results in exchange of genetic information between chromosomes.在减数分裂中的交换现象导致染色体之间的遗传信息交换在减数分裂中的交换现象导致染色体之间的遗传信息交换。6/1/2024Hence,the homologous chromosome distributed to different progeny cells are not identical.因此，分配到不同子细胞中的同源染色体是不相同的。因此，分配到不同子细胞中的同源染色体是不相同的。6/1/20246/1/2024As in mitosis two chromatids exist for each chromosome at the beginning of prophase I.正如在有丝分裂中一样，在前期正如在有丝分裂中一样，在前期I开始的时候每个染色体是以两个染色单体形式存在开始的时候每个染色体是以两个染色单体形式存在6/1/2024During 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.在这个时期，同源染色体通过蛋白质和在这个时期，同源染色体通过蛋白质和RNA组成的联会复合体进行联会或配对。组成的联会复合体进行联会或配对。The homologous pairs stay together when they align on the metaphase plate.同源染色体对一起成线形排列在中期赤道板上。同源染色体对一起成线形排列在中期赤道板上。6/1/2024Unlike 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.但是，与有丝分裂后期不同的是，在后期但是，与有丝分裂后期不同的是，在后期I，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极。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极。It is this event that results in the halving of the chromosome number in the four daughter cells that result from meiosis.由此而导致由此而导致4个子细胞中染色体数减半。个子细胞中染色体数减半。6/1/2024During telophase I nuclear envelopes enclose the chromosomes in nuclei,and in most species cytokinesis(the first nuclear division)follows.在末期在末期I，核被膜围绕着细胞核里的染色体，在大多数物种里第一次，核被膜围绕着细胞核里的染色体，在大多数物种里第一次胞质分裂紧随其后胞质分裂紧随其后 The second nuclear division begins with metaphase II,in which the chromosomes in each daughter cell again align on a metaphase plate第二次核分裂开始于分裂中期第二次核分裂开始于分裂中期II，子细胞中染色体再次重新排列在赤道板上。，子细胞中染色体再次重新排列在赤道板上。6/1/2024The centromeres finally divide,and each sister chromatid moves to one of the poles of the spindle.着丝粒最终分离，每个姊妹染色单体移向两极。着丝粒最终分离，每个姊妹染色单体移向两极。The next phase is telophase II,followed again by cytokinesis.下一个时期是末期下一个时期是末期II，紧接着是第二次，紧接着是第二次胞质分裂。胞质分裂。The result of the entire process is four haploid cells in which parental chromosomes are randomly distributed.整个减数分裂过程，产生整个减数分裂过程，产生4个亲本染色体随机分配的单倍体细胞。个亲本染色体随机分配的单倍体细胞。6/1/20246.Asexual versus sexual reproduction无性和有性生殖无性和有性生殖6/1/2024Mitosis and meiosis,respectively,make simple cell division and sexual reproduction possible.有丝分裂和减数分裂分别可以让简单的细胞分裂和有性生殖成为可能。有丝分裂和减数分裂分别可以让简单的细胞分裂和有性生殖成为可能。Each means of passing on hereditary information has advantages.每种传递遗传信息的方式各有优势。每种传递遗传信息的方式各有优势。6/1/2024 In asexual reproduction the parent organism gives rise to offspring that are genetic clones of the complement,requires little or no specialization of reproductive organs,and is more rapid than sexual reproduction.在在无无性性生生殖殖中中，子子细细胞胞就就是是亲亲本本的的克克隆隆，保保留留了了亲亲本本的的遗遗传传信信息息，亲亲本本不不需需要要生生殖殖器器官官的的特特化化，比比有有性性生生殖殖快快的的多。多。6/1/2024A major disadvantage of the asexual mode is that a single catastrophic event or disease may destroy an entire population of genetically identical organisms.无性生殖的一个主要的劣势是，一个简单灾难性事件或疾病都可能摧毁遗传上一致的整个种群。无性生殖的一个主要的劣势是，一个简单灾难性事件或疾病都可能摧毁遗传上一致的整个种群。6/1/2024A prime benefit of sexual reproduction is that it provides genetic variability and a ready mechanism for the elimination of deleterious mutations.有性生殖的首要优势是它提供了遗传变异和现存排除有害突变的机制。有性生殖的首要优势是它提供了遗传变异和现存排除有害突变的机制。It also allows“new”gene forms to arise and spread through populations.它也可以产生新的基因并在种群中传递它也可以产生新的基因并在种群中传递(蔓延蔓延)。6/1/20246/1/2024谢谢观赏！2020/11/549