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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,agricultu
2、re.,The government,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?
3、mi?,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,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,dinucleosom
4、e model,双核小体模型,chromatin fiber model,染色质纤维模型,9,Cytokinesis,?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:ni,seljul?,adj.,单细胞的,11,Histone,组蛋白,五种类型：,H1,、,H2A,、,H2
5、B,、,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,Interphase?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,?,Autoso
6、me,?,:,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,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,;,?,a
7、moral 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 dramatic,dr?,?,m,?,tik,（戏剧性的）,increase in,the spread 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 y
8、ear 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,?,cluster 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,?,nuc
9、leosomes,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,strands of DNA and,clusters,of associated,proteins.Long,stretches,of the continuous,DN
10、A 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 supercoiling produces a,dense,chromosome structure.Each long,strand of DNA comb
11、ines 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。,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?taip n.,染色体组型,?,sex chromosome,性染色体,?,homologous pairs,同源染色体对,?
12、,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 present as,two copies,referred
13、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 single set of,parenta
14、l 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 the t
15、ime-,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,?,divis
16、ion di,?,vi,?,?n,分开,34,?,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 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
17、环的存在让单细胞生物得以“长生不死”。,35,?,Many 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,
18、?,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?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 t
19、hree include G1,the,period,?,pi?ri?d 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.Together the G1,S,and G2 phases are called,interphase,.,?,正常的细
20、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 period of,mitosis,during,which the replicated chromosomes,condense,and move and the cell divides.,It is believed that,properties,of the cell,cytop
21、lasm 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
22、.,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,?,right angle,?,?,?,l,直角,?,anaphase,后期,?,draw,拖,?,telophase,末期,41,?,Biologists,divide
23、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 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
24、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 chromatids of,each chromosome split,and one from each pair is
25、,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,?,tju:bju:ln.,微管,?,crucial,?,kru:,?,?l adj.,关键
26、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,spindle forms as microt
27、ubules 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,kinetochore,s.During,anaphase the fibers begin to shorten,and the,chromatids b
28、egin 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 microfilamen
29、t,微丝收,缩环,46,?,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。,47,4,Cytok
30、inesis,:partitioning 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 anim
31、al 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 building,of a new,cell plate,across the dividing cell at,its equator.,Cell wall,material is then,depositeddi,?,p,?,
32、zitid,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。,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
33、懈的渴望印,象深刻。,51,5 Meiosis:the basis of sexual reproduction,synapsis,si?n?psis,生,染色体结合,;,联会,sexual reproduction,?seksju?l,?ri,:,pr?d?k?n,有性生殖,mitotic spindle,mi?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,?,
34、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 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,
35、(meiosis I and,meiosis,).These divisions result in four,daughter cells,each with half the number of,chromosomes 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
36、，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,crossing over,during meiosis results in,exchanges of,genetic information,between,chromosomes.Hence,the,homologous,chromosomes,distributed t
37、o 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,
38、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 structure,of proteins and,RNA called the,synaptonemal complex.,The,homologous pairs stay together
39、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,chromosome stay joined at the,centromere,and move together to one of the two poles of,the
40、 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,?,nucleus,细胞核,复数,nuclei,?,nuclear,细胞核的,?,randomly,?,r,?,nd?mli,随机地,?,metaph
41、ase 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 which the chromosomes in,each daughter cell again,ali
42、gn 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 chromosomes are,randomly,distributed.,?,第二次核分裂
43、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,?,Mitosis,?,Sexual repr
44、oduction,?,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 p
45、ri,?,z?:v,保持,?,genetic 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 organis
46、m,gives rise to,offspring,that are,genetic clones,of the parent.,The advantages of this type of reproduction are,that it,preserve,s 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
47、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
48、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,?,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,or
49、ganisms,.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,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。,
