1、1 Lesson Three Cellular Reproduction:Mitosis and Meiosis 细胞的增殖：有丝分裂和减数分裂 2 英语佳句300例之?The rapid expansion of urban areas has in many cases encroached（侵犯）on valuable cultivatable（可耕种的）land,and led to a general recognition（引起了广泛关注）that development must not be carried at the cost of agriculture.The gove
2、rnment has attached greater importance to（重视）the problem and an increasing number of redundant（多余的）projects are being terminated.?城区的迅速扩大在很多情况下侵占了宝贵的可耕地，使人们普遍认识到发展不能以牺牲农业为代价。政府更加重视这个问题，越来越多的不必要的工程被终止。3 Metaphase plate 赤道板，中期板 4 Cell plate 细胞板 5 Chromatid 染色单体 Centromere?sentr?mi?着丝粒着丝粒 染色体上一段非编码的DNA
3、,对动粒（或动粒蛋白）有组织和整合作用 6 Chalone?k?l?un :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。?Mammalian m?me?lj?n:n.哺乳动物 adj.哺乳动物的?Homogenate h?m?d?ineit:n.均匀混合物,生(组织)匀浆 7 Nucleosome?nju:kli?s?um 核小体 8 Chromatin?kr?um?tin 染色质 core particle 核心颗粒 dinucleosome model 双核小体模型 chromatin fiber model 染色质纤维模型 9 Cy
4、tokinesis?sait?ukai?ni:sis 胞质分裂 10?Diploid?dipl?id 二倍体，双倍的?Bi,di,dipl,twi,du/前缀/二，双，两?Haploid?h?pl?id 单倍体?Hapl(o)-,mono-,uni-/前缀/单，一，独?Monoxide m?n?k?sa?d 一氧化物?unicellular ju:niseljul?adj.单细胞的 11 Histone 组蛋白 五种类型：H1、H2A、H2B、H3、H4 12 Homologoush?m?l?s pair 同源染色体对 13 Karyotype?k?ri?taip 核型，染色体组型 14 In
5、terphase?int?(:)feiz 分裂间期 15 Prophase 分裂前期 Spindle 纺锤体 16 Anaphase?n?feiz 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 17 Telophase?tel?feiz 分裂末期 18 Metaphase?met?feiz 分裂中期 19 Mitosis 有丝分裂 20?Autosome?:t?s?um n.正染色体,常染色体?Kinetochore ki?ni:t?k?:n.生动粒；着丝粒?Partition p:?ti?n n.分割,划分,瓜分,分开,隔离物;vt.区分,隔开,
6、分割 21?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?pr?d?ni:n.后裔,后代?a-,an-(元音前用)无，非?asexualei?seksju?l 无性繁殖的;?abacterial 非细菌性的;?amoral e?m?:r?l无道德感的?asymmetric?s?metr?k 不对称的;22 Meiosis mai?usis 减数分裂 23 英语佳句300例之?There has been a dramaticdr?m?tik（戏剧性的）（戏剧性的）increase in the sprea
7、d of AIDS in recent years,with a new study projecting that the dreaded（令人畏惧的）disease will affect over 30 million people worldwide by the year 2005.近年来，艾滋病蔓延的幅度进一步扩大，一项新的研究预测，到2005年，世界上有超过三千万人将感染这一可怕的疾病。24 Text:1 The nucleus and chromosome 25?repository r?p?z?t?:ri:储藏室?coil k?il v.螺旋 supercoil?cluste
8、r n.丛；簇，串；群?stretch stret?n.伸展；延伸?wind around 缠绕?histones n.组蛋白 nonhistone 非组蛋白的?beadlike 串珠状的?nucleosomes 核小体?dense dens 致密的?combine k?m?bain v.使结合?chromatin.染色质?chromosome 染色体 26?The cell nucleus is the main repository of genetic information.Within the nucleus are the chromosomes-tightly coiled st
9、rands 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。细胞核内有染色体，包括由DNA紧密盘绕成的螺旋线以及相关的成簇蛋白质。连续的DNA链缠绕成簇的组蛋白,形成珠链状的核小体。27?More coiling and supercoi
10、ling produces a dense chromosome structure.Each long strand of DNA combines with histones and nonhistone proteins to make up the substance chromatin.?这些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。与组蛋白和非组蛋白一起构成染色质。28?pictorial p?k?t?:ri:?l adj.绘画的；有图片的；图画似的?condense k?n?densvt.变浓缩；使更紧密?karyotype?k?ri?ta
11、ip n.染色体组型?sex chromosome 性染色体?homologous pairs 同源染色体对?autosomes 常染色体?organism?:?niz?m 有机体?diploid?dipl?id 二倍体?haploid?h?pl?id 单倍体 29?A pictorial display of an organisms chromosomes in the coiled,condensed state is known as a karyotype.Karyotype reveal that in most cells all but sex chromosomes are
12、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。30?Organisms whose cells contain two sets of parentalp?rentl chromosomes are called diploid;those with cells containing a sing
13、le 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。31 2 The cell cycle The cycle is divided into distinct phases:G1(gap 1)S(synthesis),G2(gap 2),and M(mitosis).As you can see,mitosis only occupies（占据）a fraction（小部分）of the cycle.The rest of t
14、he time-phases G1 through G2-is known as interphase.32 2 The cell cycle 33?regular 有规律的?divide 划分 分离?repeat vt.重复?in effect 实际上?single-celled 单细胞的?immortal i?m?:tl adj.不死的；永恒的?multicellular?m?lti?seljul?多细胞的?muscle?m?sl n.肌肉?nerve n?:v n.神经?altogether 完全地?division di?vi?n 分开 34?The cell cycle is a r
15、egular sequence in which the cell grows,prepares for division,and divides to form two daughter cells,each of which then repeats the cycle.Such cycling in effect makes single-celled organisms immortal.?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”。35?Many cells in multicellular or
16、ganisms,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，包括动物肌细胞和神经细胞，要么细胞循环速度降低，要么全部从这个循环中脱离。36?metabolismmai?t?b?l?z?mn.新陈代谢?replicate?repl?ke?tvt.复制?histone?hist?un 组蛋白?synthesize?s?n?sa?z vi.合成?interphase?int?(:)feizn.（细胞的）间期?mitosis英 mi?t?
17、usis 美 ma?tos?s?condense k?n?dens vt.变稠或变浓，浓缩?property?pr?p?ti n.特性，属性?inhibitor in?hibit?n.抑制剂?chalones 抑素 37?The normal cell cycle consists of four phases.The first three include G1,the period?pi?ri?d of normal metabolism;S phase,during which normal synthesis of biological molecules continues,DNA
18、is replicated,and histones are synthesized;and G2,a brief period of metabolism 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。38?The fourth phase of the cell cycle is M phase,the
19、period of mitosis,during which the replicated chromosomes condense and move and the cell divides.It is believed that properties of the cell cytoplasm control the cell cycle,along with externaleks?t?: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
20、激物、抑制因子如抑素等控制了细胞循环。39 3 Mitosis:partitioning the hereditary material p:?ti?ni?n.分割 hi?redit?ri adj.遗传的 40?Biologistba?l?d?st n.生物学家?mitotic cyclemi?t?tik 有丝分裂周期?prophase 前期?chromatid?kr?um?tidn.染色单体?centromere?sentr?mi?n.着丝粒?metaphase 中期?spindle?sp?ndl 生纺锤体?Eventuallyi?ventju?li adv.终于?plane n.水平；平面
21、?right angle?l 直角?anaphase 后期?draw 拖?telophase 末期 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 chromosome
22、s become associated 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。42?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。?Next,during anaphase,the two sister chromat
23、ids of each chromosome split,and one from each pair is drawn toward each pole of the cell.During telophase nuclear envelopes?env?l?ups 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?microtubule?maikr?u?tj
24、u:bju:ln.微管?crucial?kru:?l adj.关键性的，决定性的；?metaphase plate 赤道板?centromeric医着丝粒的?kinetochore ki?ni:t?k?:n.动粒 44?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.Each half of the spind
25、le forms as microtubules extend from each pole of a dividing cell to the region of the metaphase plate.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
26、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。在分裂后期，纤维开始变短，染色单体分离。45?centriole?sentri?uln.细胞中心粒，中心体?fungal?f?ladj.真菌的 fungus 真菌?cleavage furrow?kli:v?d?f?:r?卵裂沟?contracting ring of microfilament微丝收缩环 46?The spindle f
27、orms 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，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。47 4 Cytokinesis:par
28、titioning the cytoplasm 卵裂沟 48?cytokinesis?sait?ukai?ni:sis 胞质分裂?actin filaments 肌动纤维丝?equator i?kweit?n.赤道?pinch pint?vt.捏，掐；挤痛，夹痛?Cell wall 细胞壁?deposite 沉积?cell plate 细胞板 49?The division of the cell cytoplasm at the end of mitosis is called cytokinesis.In animal cells it takes place as a ring of a
29、ctin filaments contracts around the cell equator,pinching the cell in two.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 depositeddi?p?zitid in the region of the cell plate.?在动物细
30、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。50 英语佳句300例之?Working with the disabled cannot help but（不得不)leave one impressed with(留下深刻印象)their indefatigable?nd?f?t?g?b?l 不屈不挠的 desire.?与残疾人一起工作使一个人不得不对他们坚持不懈的渴望印象深刻。51 5 Meiosis:the basis of sexual reproduction synapsis si?n?p
31、sis 生染色体结合;联会 sexual reproduction?seksju?l?ri:pr?d?k?n 有性生殖 mitotic spindlemi?t?tik 有丝分裂纺锤丝 52 meiosis Fig.meiosis in a plant pollen grain.花粉粒?p?l?n 53?reproductive organs?ri:pr?d?kt?v 生殖器官?sequential s?kwen?l 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 54?Meiosis is a special form
32、 of cell division that takes 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 chromos
33、omes of the parent cell.?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。55?phenomenon fi?n?min?n 现象?crossing over?kr?si?uv?交换，互换?exchangeiks?t?eind?交换?homologous chromosomes 同源染色体?progeny?pr?d?ni:子代 后裔?identicalai?dentik?l adj.同一的；完全同样的 56?The phenomenon of
34、 crossing over during meiosis results 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。57?undergo?nd?u 经历，遭受?synapsis si?n?psis 联会?pairing 配对?bridging 桥
35、接?synaptonemal complex 联会复合体?align?la?n 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 58?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 stru
36、cture of proteins and RNA called 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。59?Unlike the anaphase of mitosis,however,during anaphase I the two chromatids of each chrom
37、osome stay joined at the 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。60?enclose in?kl?uz 把围起来?nuc
38、leus 细胞核 复数 nuclei?nuclear 细胞核的?randomly?r?nd?mli 随机地?metaphase plate 中期板?distribute dis?tribju:t vt.分配 61?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 wh
39、ich the chromosomes 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 paren
40、tal chromosomes 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。62?Asexual ei?seksju?l adj.无性的；无性生殖的?versus?v?:s?s 与.比较?Gametes?mi:ts 配子 63 6 Asexual versus sexual reproduction 无性繁殖与有性生殖的比较?Asexual reproduction?NO exchange of genetic material?Mi
41、tosis?Sexual reproduction?Exchange of genetic material?Meiosis?Gametes 64?respectively ris?pektivli adv.各自地；分别地?pass on 传递?hereditary information hi?redit?ri 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 pri?z?:v 保持?gene
42、tic complement?k?mplim?nt 基因互补?specialization?spe?la?ze?n 特殊化 65?Mitosis and meiosis,respectively,make simple cell division and sexual reproduction possible.Each means of passing on hereditary information has advantages.In asexual reproduction the parent organism gives rise to offspring that are gen
43、etic clones of the parent.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.?有丝分裂和减数分裂在传递遗传信息过程中各有优势。体细胞的繁殖就是父母本的克隆，其优势是保留了父母本的成功遗传信息，不需要特殊
44、器官，比性复制快的多。66?mode m?ud 方式 模式?catastrophic?k?t?str?f?kadj.灾难的?variability?ve?r?b?l?t?n.变化性?genetic variability 基因的可变性?population 群体?genetically d?net?kli identical ai?dentik?l organisms 遗传性相同的有机体?prime 最好的 首要的?elimination?l?m?ne?n 排除 出去?deleterious mutations?del?t?ri:?s mju:?te?n 有害突变?arise?raiz 产生?
45、spread spred 延伸 传播 67?A major disadvantage of the asexual mode is that a single catastrophic event or disease may destroy an entire population of genetically identical organisms.A prime benefit of sexual reproduction is that it provides genetic variability and a ready mechanism for the elimination of deleterious mutations.It also allows ew gene forms to arise and spread through populations.?但一个简单灾难性事件或疾病都可能摧毁一个细胞群体。有性繁但一个简单灾难性事件或疾病都可能摧毁一个细胞群体。有性繁殖的优势是它提供了遗传可变性和现存排除有害突变的机制。也可以产生新的基因并在种群中蔓延。68 作业?用英文简单描述有丝分裂和减数分裂的过程。
