大學(xué)生物專業(yè)英語3

1、2022-4-61Lesson threeCellular reproduction: mitosis and meiosis2022-4-62objectivevUnderstand the concept of mitosis and meiosis.vControl the process of mitosis and meiosis.vDescripe the meaning of meiosis.2022-4-631. The nucleus and chromosomes2022-4-64vrepository n.貯藏室貯藏室, 智囊團(tuán)智囊團(tuán), 知識庫知識庫, 倉庫倉庫vchro

2、mosome n.生物生物染色體染色體vhistone n.生化生化組蛋白組蛋白vnucleosome n.生化生化核小體核小體vchromatin n.核染質(zhì)核染質(zhì), 染色質(zhì)染色質(zhì)vpictorial adj.圖示的圖示的 n.畫報畫報vkaryotype n.生物生物 染色體組型染色體組型vhomologous pair 同源染色體對同源染色體對vautosome n.正染色體正染色體, 常染色體常染色體vdiploid adj.雙重的雙重的, n.二倍體二倍體vhaploid n.生物生物單倍體單倍體 adj.單一的單一的2022-4-65vThe cell nucleus is the

3、 main repository of genetic information. v細(xì)胞核是貯藏遺傳信息的主要場所。細(xì)胞核是貯藏遺傳信息的主要場所。vWithin the nucleus are the chromosomestightly coiled strands of DNA and clusters of associated proteins.v細(xì)胞核里的是染色體緊密盤繞成螺旋的細(xì)胞核里的是染色體緊密盤繞成螺旋的DNA鏈和鏈和相關(guān)的成簇蛋白質(zhì)。相關(guān)的成簇蛋白質(zhì)。2022-4-66v Long stretches of the continuous DNA molecule wind

4、 around these clusters of proteins, or histones, forming beadlike complexes known as nucleosomes. v長鏈長鏈DNA分子纏繞著成簇的蛋白質(zhì)，分子纏繞著成簇的蛋白質(zhì)，或組蛋白，形成珠鏈狀的核小體?；蚪M蛋白，形成珠鏈狀的核小體。2022-4-67nucleosome 核小體， 核粒The basic unit of chromatin structure in eukaryotic cells. A nucleosome consists of eight histone molecules of fo

5、ur different types, together with about 140 base pairs of DNA coiled around it.2022-4-68vMore coiling and supercoiling produces a dense chromosome structure. v進(jìn)一步的螺旋和超螺旋形成致密的染色體組進(jìn)一步的螺旋和超螺旋形成致密的染色體組結(jié)構(gòu)。結(jié)構(gòu)。vEach long strand of DNA combine with histones and nonhistone proteins to make up the substance c

6、hromatin.v每個長鏈每個長鏈DNA與組蛋白和非組蛋白一起構(gòu)成與組蛋白和非組蛋白一起構(gòu)成染色質(zhì)物質(zhì)。染色質(zhì)物質(zhì)。 2022-4-69vA pictorial display of an organisms chromosomes in the coiled, condensed state is known as a karyotype.v生物體中的致密的超螺旋狀態(tài)的染色體的表型稱為核生物體中的致密的超螺旋狀態(tài)的染色體的表型稱為核型型.vKaryotype reveal that in most cells all but sex chromosomes are present as t

7、wo copies, referred to as homologous pairs. v表型顯示：在大多數(shù)細(xì)胞里，除了性染色體外，其它表型顯示：在大多數(shù)細(xì)胞里，除了性染色體外，其它的染色體都是成對出現(xiàn)的，稱之為同源染色體對。的染色體都是成對出現(xiàn)的，稱之為同源染色體對。2022-4-610homologous pair 同源染色體對Chromosomes that pair during meiosis. Each homologous is a duplicate of one of the chromosomes contributed at syngamy(融合生融合生殖，有性生殖殖，有

8、性生殖)by the mother or father. Homologous chromosomes contain the same linear sequence of genes and as a consequence each gene is present in duplicate.2022-4-611vNon-sex chromosomes are called autosomes. v非性染色體稱常染色體。非性染色體稱常染色體。vOrganisms whose cells contain two sets of parental chromosomes are called

9、diploid; those with cells containing a single set of parental chromosomes are called haploid.v細(xì)胞里含有兩套親本染色體的生物體稱二倍細(xì)胞里含有兩套親本染色體的生物體稱二倍體；細(xì)胞里含有單套染色體的生物體稱單倍體；細(xì)胞里含有單套染色體的生物體稱單倍體。體。2022-4-6122. The cell cycle細(xì)胞周期細(xì)胞周期2022-4-613vimmortal adj.不朽的不朽的vChalone n.生化生化抑素抑素vprophase n. (細(xì)胞分裂細(xì)胞分裂)前期前期vchromatid n.生物

10、生物染色單體染色單體vcentromere n.生生著絲點著絲點, 著絲粒著絲粒vmetaphase n.中期中期vanaphase n.生生(細(xì)胞分裂的細(xì)胞分裂的)后期后期2022-4-614vThe 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.v細(xì)胞周期遵循特定的程序：細(xì)胞生長，分裂細(xì)胞周期遵循特定的程序：細(xì)胞生長，分裂準(zhǔn)

11、備，分裂成準(zhǔn)備，分裂成2個子細(xì)胞，每個子細(xì)胞再循環(huán)。個子細(xì)胞，每個子細(xì)胞再循環(huán)。 vSuch cycling in effect makes single-celled organisms immortal. v此循環(huán)可以有效的使得單細(xì)胞生物永生。此循環(huán)可以有效的使得單細(xì)胞生物永生。 2022-4-615vMany cells in multicellular organisms, including animal muscle and nerve cells, either slow the cycle or break out of it altogether.v多細(xì)胞生物中的許多細(xì)胞，包

12、括動物肌肉和神多細(xì)胞生物中的許多細(xì)胞，包括動物肌肉和神經(jīng)細(xì)胞，要么減慢周期速度，要么一起脫離細(xì)經(jīng)細(xì)胞，要么減慢周期速度，要么一起脫離細(xì)胞周期。胞周期。vThe normal cell cycle consists of four phases. v正常細(xì)胞周期由正常細(xì)胞周期由4個時期組成。個時期組成。2022-4-616vThe first three include G1, the period of normal metabolism; S phase, during which normal synthesis of biological molecules continues, DNA

13、 is replicated, and histones are synthesized; and G2, a brief period of metabolism and additional growth. v前三個時期包括前三個時期包括G1,正常新陳代謝時期；正常新陳代謝時期；S期期,生物生物分子的合成繼續(xù)，同時，分子的合成繼續(xù)，同時，DNA復(fù)制，組蛋白合成；復(fù)制，組蛋白合成； G2 期，新陳代謝和進(jìn)一步生長的短暫時期。期，新陳代謝和進(jìn)一步生長的短暫時期。vTogether the G1, S, and G2 phases are called interphase. vG1, S, 和

14、和G2一起稱為分裂間期。一起稱為分裂間期。2022-4-617vThe 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. v細(xì)胞周期的第四個時期是細(xì)胞周期的第四個時期是M期，有絲期，有絲分裂期，復(fù)制的染色體濃縮，移動并分裂期，復(fù)制的染色體濃縮，移動并細(xì)胞分裂。細(xì)胞分裂。2022-4-618vIt is believed that properties of

15、 the cell cytoplasm control the cell cycle, along with external stimulators and inhibitors such as chalones.v據(jù)稱是細(xì)胞質(zhì)中的物質(zhì)與外來的激活因子和據(jù)稱是細(xì)胞質(zhì)中的物質(zhì)與外來的激活因子和抑制因子如抑素等一起控制了細(xì)胞周期。抑制因子如抑素等一起控制了細(xì)胞周期。 2022-4-6193. Mitosis: partitioning the hereditary material有絲分裂：有絲分裂：遺傳物質(zhì)的分離遺傳物質(zhì)的分離2022-4-620vTelophase n.生生(細(xì)胞有絲分裂的細(xì)

16、胞有絲分裂的)末期末期vkinetochore n.生生動粒動粒, 著絲粒著絲粒, 著絲著絲點點vcytokinesis n.胞質(zhì)分裂胞質(zhì)分裂vpinching v.收聚收聚vcell plate 細(xì)胞板細(xì)胞板vmitosis n.有絲分裂有絲分裂vmeiosis n.減數(shù)分裂減數(shù)分裂, 成熟分裂成熟分裂2022-4-621vBiologists divide the mitotic cycle into four phases. v生物學(xué)家將有絲分裂劃分為生物學(xué)家將有絲分裂劃分為4個階段。個階段。vAt the beginning of prophase the chromosomes ea

17、ch consist of two highly condensed chromatids attached to each other at a centromere. v分裂前期，每個染色體是由高度濃縮的通過分裂前期，每個染色體是由高度濃縮的通過著絲粒連接在一起的兩個染色單體組成。著絲粒連接在一起的兩個染色單體組成。(分分裂前期，高度濃縮的兩個染色單體通過著絲裂前期，高度濃縮的兩個染色單體通過著絲粒連接在一起形成染色體粒連接在一起形成染色體)2022-4-622v紡錘絲出現(xiàn)：紡錘絲出現(xiàn)：vThe spindles begin to occur.v前期末核仁核膜的消失：前期末核仁核膜的消失：

18、 nuclear envelope have dispersed and nucleoli broken down at the end of prophase.2022-4-623vAs prophase ends and metaphase begins, the condensed chromosomes become associated with the spindle.v分裂前期結(jié)束，緊接著是分裂中期，濃縮的分裂前期結(jié)束，緊接著是分裂中期，濃縮的染色體與紡錘體相連。染色體與紡錘體相連。(在分裂前期后期和分在分裂前期后期和分裂中期前期，濃縮的染色體與紡錘體相連裂中期前期，濃縮的染色體

19、與紡錘體相連)vEventually the chromosomes become arranged in a plane (called the metaphase plate) at a right angle to the spindle fiber.v最后染色體在紡錘絲的牽引下以最后染色體在紡錘絲的牽引下以正確的角度正確的角度排列在赤道板上。排列在赤道板上。2022-4-624vNext, during anaphase, the two sister chromatids of each chromosome split, and one from each pair is draw

20、n toward each pole of the cell.v在分裂后期，兩個姊妹染色單體分離，分別被在分裂后期，兩個姊妹染色單體分離，分別被拉向細(xì)胞兩極。拉向細(xì)胞兩極。 2022-4-625During telophase nuclear envelope begin to form around each set of chromosomes, and division of the cytoplasm takes place. 在分裂末期，在每套染色體周圍形成核膜，在分裂末期，在每套染色體周圍形成核膜，細(xì)胞質(zhì)分裂發(fā)生細(xì)胞質(zhì)分裂發(fā)生。Each chromatids reaches a p

21、ole of the cell.染色體到達(dá)兩極染色體到達(dá)兩極.2022-4-626vAs 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.v在有絲分裂過程中，紡錘體微管在確保染色單在有絲分裂過程中，紡錘體微管在確保染色單體配對和在適當(dāng)時間以正確方向進(jìn)行分離中發(fā)體配對和在適當(dāng)時間以正確方向進(jìn)行分離中發(fā)揮了關(guān)鍵性的作用

22、。揮了關(guān)鍵性的作用。 vEach half of the spindle forms as microtubules extend from each pole of a dividing cell to the region of the metaphase plate.v微管從正在分裂的細(xì)胞兩極向赤道板延伸，微管從正在分裂的細(xì)胞兩極向赤道板延伸，就就形成了紡錘體的一半。形成了紡錘體的一半。v 2022-4-627v During prophase, other microtubules, the centromeric fiber, extend outward from the spin

23、dle poles to structures on the chromosomes called kinetochores. v在分裂前期，其它微管，著絲粒纖維從紡錘體的兩在分裂前期，其它微管，著絲粒纖維從紡錘體的兩極延伸到染色體的動粒區(qū)域。極延伸到染色體的動粒區(qū)域。vDuring anaphase the fibers begin to shorten, and the chromatids begin to move apart.在分裂后期，纖維開始變短，染色單體分離在分裂后期，纖維開始變短，染色單體分離。2022-4-628著絲粒（著絲粒（centromere）：）：位于染色體縊縮部位

24、，是位于染色體縊縮部位，是異染色質(zhì)，是在染色體最異染色質(zhì)，是在染色體最后復(fù)制的部位。著絲粒在后復(fù)制的部位。著絲粒在染色體上的位置是確定的。染色體上的位置是確定的。動粒（動粒（kinetochore）：位）：位于著絲粒外側(cè)的蛋白質(zhì)復(fù)于著絲粒外側(cè)的蛋白質(zhì)復(fù)合體。合體。2022-4-629vThe spindle forms differently in plant and animal cells. 植物和動物細(xì)胞中的紡錘體的形成是不同的。植物和動物細(xì)胞中的紡錘體的形成是不同的。In animal it is associated with centriole, while in plant an

25、d fungal cells spindle formation is associated with regions called microtubule organizing centers. 在動物中，紡錘體的形成與中心粒相關(guān)，而在在動物中，紡錘體的形成與中心粒相關(guān)，而在植物和真菌細(xì)胞中，紡錘體的形成與微管組織植物和真菌細(xì)胞中，紡錘體的形成與微管組織中心相關(guān)。中心相關(guān)。 2022-4-6304. Cytokinesis: Partitioning the cytoplasm胞質(zhì)分裂：細(xì)胞質(zhì)分離胞質(zhì)分裂：細(xì)胞質(zhì)分離2022-4-631vThe division of the cell cy

26、toplasm at the end of mitosis is called cytokinesis. v在有絲分裂結(jié)束時，細(xì)胞質(zhì)的分裂稱為在有絲分裂結(jié)束時，細(xì)胞質(zhì)的分裂稱為胞質(zhì)分裂。胞質(zhì)分裂。vIn animal cells it takes place as a ring of actin filaments contracts around the cell equator, pinching the cell in two. v 在動物細(xì)胞中，在動物細(xì)胞中，環(huán)形的肌動蛋白環(huán)形的肌動蛋白纖維圍纖維圍繞赤道板收縮，將細(xì)胞一分為二。繞赤道板收縮，將細(xì)胞一分為二。2022-4-632vIn

27、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.v在植物細(xì)胞中，被細(xì)胞壁包圍，胞質(zhì)分裂涉及到在植物細(xì)胞中，被細(xì)胞壁包圍，胞質(zhì)分裂涉及到在在正在分裂的細(xì)胞的赤道板上正在分裂的細(xì)胞的赤道板上新的細(xì)胞板的形成。新的細(xì)胞板的形成。 (在植物細(xì)胞中，在赤道板形成新的細(xì)胞板。在植物細(xì)胞中，在赤道板形成新的細(xì)胞板。 )vCell wall material is then de

28、posited in the region of the cell plate.v然后，細(xì)胞壁材料在細(xì)胞板區(qū)域沉積然后，細(xì)胞壁材料在細(xì)胞板區(qū)域沉積2022-4-633Operation of the Contractile Ringduring Cytokinesis2022-4-634 5. Meiosis: the basis of sexual reproduction減數(shù)分裂：有性生殖的基礎(chǔ)減數(shù)分裂：有性生殖的基礎(chǔ)2022-4-635vHalving 對分對分, 二等分二等分, 減半減半vSynapsis 聯(lián)會聯(lián)會vsynaptinemal complex 聯(lián)會復(fù)合物聯(lián)會復(fù)合物2022

29、-4-636vMeiosis is a special form of cell division that takes place in the reproductive organs that produce sex cells. v減數(shù)分裂是發(fā)生在產(chǎn)生性細(xì)胞的生殖器官中的一種減數(shù)分裂是發(fā)生在產(chǎn)生性細(xì)胞的生殖器官中的一種特殊的分裂形式。特殊的分裂形式。(減數(shù)分裂是性細(xì)胞分裂的特殊形減數(shù)分裂是性細(xì)胞分裂的特殊形式。式。 )vLike mitosis, it takes place after DNA replication has occurred and involves two sequ

30、ential nuclear divisions (meiosis I and meiosis II). v如有絲分裂，它也是發(fā)生在如有絲分裂，它也是發(fā)生在DNA復(fù)制后，并有兩個復(fù)制后，并有兩個連續(xù)的核分裂。連續(xù)的核分裂。2022-4-637vThese division results in four daughter cells, each with half the number of chromosomes of the parent cell. v減數(shù)分裂產(chǎn)生減數(shù)分裂產(chǎn)生4個子細(xì)胞，分別含有親本一半個子細(xì)胞，分別含有親本一半的染色體數(shù)。的染色體數(shù)。vThe phenomenon of

31、 crossing over during meiosis results in exchange of genetic information between chromosomes. v在減數(shù)分裂中的交換現(xiàn)象導(dǎo)致染色體之間的在減數(shù)分裂中的交換現(xiàn)象導(dǎo)致染色體之間的遺傳信息交換遺傳信息交換。2022-4-638vHence, the homologous chromosome distributed to different progeny cells are not identical.v因此，分配到不同子細(xì)胞中的同源染色因此，分配到不同子細(xì)胞中的同源染色體是不相同的。體是不相同的。2022

32、-4-639vAs in mitosis two chromatids exist for each chromosome at the beginning of prophase I. v正如在有絲分裂中一樣，在前期正如在有絲分裂中一樣，在前期I開開始的時候每個染色體是以兩個染色始的時候每個染色體是以兩個染色單體形式存在單體形式存在2022-4-640v細(xì)線期細(xì)線期： leptotene: vchromosomes condense highly;偶線期偶線期： zygotene:聯(lián)會聯(lián)會： The homologous chromosomes pair all along their le

33、ngth. The process of forming these complexes of homologous chromosomes is called synapsis. This is first feature of meiosis.2022-4-641vThe structure of the synaptinemal complex is present between the homologous chromosomesv聯(lián)會復(fù)合體位于同源染色體之間聯(lián)會復(fù)合體位于同源染色體之間：v粗線期粗線期：pachytene vThe paired homologous chromos

34、omes continue to condense, and each pair is called bivalent. Each pair of homologous chromosomes contains four chromatids, and it is called tetrad.v配對的同源染色體被稱為二價體，每條染色體包含4條染色單體，因此稱為四價體：2022-4-642v雙線期雙線期：diplotene vCrossing over can occur between nonsister chromatids. Meiosis results in the genetic e

35、xchanges of maternal and paternal chromosomes. This is second feature of meiosis.非姐們?nèi)旧w之間發(fā)生交換，這導(dǎo)致父母本的遺傳物質(zhì)發(fā)生交換，這是減數(shù)分裂的第二特點。2022-4-643vDuring this phase the homologous chromosomes undergo synapsis, or pairing, which is brought about by a bridging structure of proteins and RNA called the synaptinemal c

36、omplex.v在這個時期，同源染色體通過蛋白質(zhì)和在這個時期，同源染色體通過蛋白質(zhì)和RNA橋配對形成聯(lián)會復(fù)合體。橋配對形成聯(lián)會復(fù)合體。vThe homologous pairs stay together when they align on the metaphase plate.v同源染色體對一起成線形排列在中期赤道同源染色體對一起成線形排列在中期赤道板上。板上。2022-4-644vUnlike the anaphase of mitosis, however, during anaphase I the two chromatids of each chromosome stay jo

37、ined at the centromere and move together to one of the two poles of the cell. 但是，與有絲分裂后期不同的是，在后期但是，與有絲分裂后期不同的是，在后期I，每組染，每組染色體的兩個染色單體連接在著絲點上并一起移向細(xì)胞色體的兩個染色單體連接在著絲點上并一起移向細(xì)胞兩極的一極。兩極的一極。vIt is this event that results in the halving of the chromosome number in the four daughter cells that result from meio

38、sis.v由此而導(dǎo)致由此而導(dǎo)致4個子細(xì)胞中染色體數(shù)減半。個子細(xì)胞中染色體數(shù)減半。2022-4-645vDuring telophase I nuclear envelopes enclose the chromosomes in nuclei, and in most species cytokinesis (the first nuclear division) follows. v在末期在末期I，核被膜圍繞著細(xì)胞核里的染色體，在大多，核被膜圍繞著細(xì)胞核里的染色體，在大多數(shù)物種里第一次數(shù)物種里第一次胞質(zhì)分裂緊隨其后胞質(zhì)分裂緊隨其后vThe second nuclear division be

39、gins with metaphase II, in which the chromosomes in each daughter cell again align on a metaphase platev第二次核分裂開始于分裂中期第二次核分裂開始于分裂中期II ，子細(xì)胞中染色體，子細(xì)胞中染色體再次重新排列在赤道板上。再次重新排列在赤道板上。 2022-4-646vThe centromeres finally divide, and each sister chromatid moves to one of the poles of the spindle.v著絲粒最終分離，每個姊妹染色單

40、體移向兩極。著絲粒最終分離，每個姊妹染色單體移向兩極。vThe next phase is telophase II, followed again by cytokinesis.v下一個時期是末期下一個時期是末期II，緊接著是第二次，緊接著是第二次胞質(zhì)分裂。胞質(zhì)分裂。v The result of the entire process is four haploid cells in which parental chromosomes are randomly distributed. v整個減數(shù)分裂過程，產(chǎn)生整個減數(shù)分裂過程，產(chǎn)生4個親本染色體隨機分配的個親本染色體隨機分配的單倍體細(xì)胞。單倍體細(xì)胞。2022-4-6476. Asexual ver