大學(xué)生物專業(yè)英語(yǔ)lesson-three

LessonthreeCellularreproduction:mitosisandmeiosis11/6/2024repositoryn.貯藏室,智囊團(tuán),知識(shí)庫(kù),倉(cāng)庫(kù)chromosomen.[生物]染色體histone

n.[生化]組蛋白nucleosomen.[生化]核小體chromatinn.核染質(zhì),染色質(zhì)pictorialadj.圖示的n.畫(huà)報(bào)karyotypen.[生物]染色體組型homologouspair

同源染色體對(duì)autosomen.正染色體,常染色體11/6/2024diploidadj.雙重的,n.二倍體haploidn.[生物]單倍體adj.單一的immortaladj.不朽的Chalonen.[生化]抑素prophasen.(細(xì)胞分裂)前期chromatidn.[生物]染色單體centromeren.[生]著絲點(diǎn),著絲粒metaphasen.中期anaphasen.[生](細(xì)胞分裂的)后期11/6/2024Telophasen.[生](細(xì)胞有絲分裂的)末期kinetochoren.[生]動(dòng)粒,著絲粒,著絲點(diǎn)cytokinesisn.細(xì)胞漿移動(dòng),原漿移動(dòng)pinchingv.收聚cellplate

細(xì)胞板mitosisn.有絲分裂meiosisn.減數(shù)分裂,成熟分裂11/6/2024Halving對(duì)分,二等分,減半Synapsis

聯(lián)會(huì)synaptinemalcomplex

聯(lián)會(huì)復(fù)合物Asexualadj.無(wú)性的,無(wú)性生殖的catastrophicadj.悲慘的,災(zāi)難的Eliminationn.排除,除去,消除,消滅11/6/20241.Thenucleusandchromosomes11/6/2024Thecellnucleusisthemainrepositoryofgeneticinformation.細(xì)胞核是貯藏遺傳信息的主要場(chǎng)所。Withinthenucleusarethechromosomes—tightlycoiledstrandsofDNAandclustersofassociatedproteins.細(xì)胞核里的是染色體－－緊密盤(pán)繞成螺旋的DNA鏈和相關(guān)的成簇蛋白質(zhì)。11/6/2024

LongstretchesofthecontinuousDNAmoleculewindaroundtheseclustersofproteins,orhistones,formingbeadlikecomplexesknownasnucleosomes.長(zhǎng)鏈DNA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。11/6/2024Morecoilingandsupercoilingproducesadensechromosomestructure.進(jìn)一步的螺旋和超螺旋形成致密的染色體組結(jié)構(gòu)。EachlongstrandofDNAcombinewith

histonesandnonhistoneproteinstomakeupthesubstancechromatin.每個(gè)長(zhǎng)鏈DNA與組蛋白和非組蛋白一起構(gòu)成染色質(zhì)物質(zhì)。

11/6/2024Apictorialdisplayofanorganism'schromosomesinthecoiled,condensedstateisknownasakaryotype.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Karyotype

revealthatinmostcellsallbutsexchromosomesarepresentastwocopies,referredtoashomologouspairs.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(duì)出現(xiàn)的，稱之為同源染色體對(duì)。11/6/2024Non-sexchromosomesarecalledautosomes.非性染色體稱常染色體。Organismswhosecellscontaintwosetsofparentalchromosomesarecalleddiploid;thosewithcellscontainingasinglesetofparentalchromosomesarecalledhaploid.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。11/6/202411/6/20242.Thecellcycle

細(xì)胞周期11/6/2024Thecellcycleisaregularsequenceinwhichthecellgrows,preparesfordivision,anddividestoformtwodaughtercells,eachofwhichthenrepeatsthecycle.細(xì)胞周期遵循特定的程序：細(xì)胞生長(zhǎng)，分裂準(zhǔn)備，分裂成2個(gè)子細(xì)胞，每個(gè)子細(xì)胞再循環(huán)。

Suchcyclingineffectmakessingle-celledorganismsimmortal.此循環(huán)可以有效的使得單細(xì)胞生物永生。

11/6/2024Manycellsinmulticellularorganisms,includinganimalmuscleandnervecells,eitherslowthecycleorbreakoutofitaltogether.多細(xì)胞生物中的許多細(xì)胞，包括動(dòng)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)胞周期。Thenormalcellcycleconsistsoffourphases.正常細(xì)胞周期由4個(gè)時(shí)期組成。11/6/2024ThefirstthreeincludeG1,theperiodofnormalmetabolism;Sphase,duringwhichnormalsynthesisofbiologicalmoleculescontinues,DNAisreplicated,andhistonesaresynthesized;andG2,abriefperiodofmetabolismandadditionalgrowth.前三個(gè)時(shí)期包括G1,正常新陳代謝時(shí)期；S期,生物分子的合成繼續(xù)，同時(shí)，DNA復(fù)制，組蛋白合成；G2期，新陳代謝和進(jìn)一步生長(zhǎng)的短暫時(shí)期。TogethertheG1,S,andG2phasesarecalledinterphase.G1,S,和G2一起稱為分裂間期。11/6/2024ThefourthphaseofthecellcycleisMphase,theperiodofmitosis,duringwhichthereplicatedchromosomescondenseandmoveandthecelldivides.細(xì)胞周期的第四個(gè)時(shí)期是M期，有絲分裂期，復(fù)制的染色體濃縮，移動(dòng)并細(xì)胞分裂。11/6/2024Itisbelievedthatpropertiesofthecellcytoplasmcontrolthecellcycle,alongwithexternalstimulatorsandinhibitorssuchaschalones.據(jù)稱是細(xì)胞質(zhì)中的物質(zhì)與外來(lái)的激活因子和抑制因子如抑素等一起控制了細(xì)胞周期。

11/6/20243.Mitosis:partitioningthehereditarymaterial

有絲分裂：

遺傳物質(zhì)的分離11/6/2024Biologistsdividethemitoticcycleintofourphases.生物學(xué)家將有絲分裂劃分為4個(gè)階段。Atthebeginningofprophasethechromosomeseachconsistoftwohighlycondensedchromatidsattachedtoeachotheratacentromere.分裂前期，每個(gè)染色體是由高度濃縮的通過(guò)著絲粒連接在一起的兩個(gè)染色單體組成。(分裂前期，高度濃縮的兩個(gè)染色單體通過(guò)著絲粒連接在一起形成染色體)11/6/2024Asprophaseendsandmetaphasebegins,thecondensedchromosomesbecomeassociatedwiththespindle.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。(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)Eventuallythechromosomesbecomearrangedinaplane(calledthemetaphaseplate)atarightangletothespindlefiber.最后染色體在紡錘絲的牽引下以正確的角度排列在赤道板上。11/6/2024Next,duringanaphase,thetwosisterchromatidsofeachchromosomesplit,andonefromeachpairisdrawntowardeachpoleofthecell.在分裂后期，兩個(gè)姊妹染色單體分離，分別被拉向細(xì)胞兩極。Duringtelophasenuclearenvelopebegintoformaroundeachsetofchromosomes,anddivisionofthecytoplasmtakesplace.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。11/6/2024Asmitosisproceeds,thespindlemicrotubulesplayacrucialroleinensuringthatbothpairedandseparatedchromatidsmoveintherightdirectionsatthepropertimes.在有絲分裂過(guò)程中，紡錘體微管在確保染色單體配對(duì)和在適當(dāng)時(shí)間以正確方向進(jìn)行分離中發(fā)揮了關(guān)鍵性的作用。

Eachhalfofthespindleformsasmicrotubulesextendfromeachpoleofadividingcelltotheregionofthemetaphaseplate.微管從正在分裂的細(xì)胞兩極向赤道板延伸，就形成了紡錘體的一半。

11/6/2024

Duringprophase,othermicrotubules,thecentromericfiber,extendoutwardfromthespindlepolestostructuresonthechromosomescalledkinetochores.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(dòng)粒區(qū)域。Duringanaphasethefibersbegintoshorten,andthechromatidsbegintomoveapart.

在分裂后期，纖維開(kāi)始變短，染色單體分離。

11/6/2024Mitosis: prophase metaphase anaphase telophasechromosomecondensationmitoticspindleassemblynuclearenvelopebreakdownchromosomesaligninthecentralplanesisterchromatidssplitandaredrawnbythespindletowardsthepolesProphaseSisterchromatidsPrometaphaseMetaphaseAnaphaseCytokinesisTelophaseInterphaseCentrosomeMicrotubulespindlemicrotubulesattachtokinetochorenuclearenvelopereforms11/6/2024著絲粒（centromere）：位于染色體縊縮部位，是異染色質(zhì)，是在染色體最后復(fù)制的部位。著絲粒在染色體上的位置是確定的。動(dòng)粒（kinetochore）：位于著絲粒外側(cè)的蛋白質(zhì)復(fù)合體。11/6/202411/6/2024Thespindleformsdifferentlyinplantandanimalcells.

植物和動(dòng)物細(xì)胞中的紡錘體的形成是不同的。

Inanimalitisassociatedwithcentriole,whileinplantandfungalcellsspindleformationisassociatedwithregionscalledmicrotubuleorganizingcenters.

在動(dòng)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中心相關(guān)。

11/6/20244.Cytokinesis:Partitioningthecytoplasm

胞質(zhì)分裂：細(xì)胞質(zhì)分離11/6/2024Thedivisionofthecellcytoplasmattheendofmitosisiscalledcytokinesis.在有絲分裂結(jié)束時(shí)，細(xì)胞質(zhì)的分裂稱為胞質(zhì)分裂。Inanimalcellsittakesplaceasaringofactinfilamentscontractsaroundthecellequator,pinchingthecellintwo.

在動(dòng)物細(xì)胞中，環(huán)形的肌動(dòng)蛋白纖維圍繞赤道板收縮，將細(xì)胞一分為二。11/6/2024Inplantcells,whichareboundedbyacellwall,cytokinesisinvolvesthebuildingofanewcellplateacrossthedividingcellatits

equator.在植物細(xì)胞中，被細(xì)胞壁包圍，胞質(zhì)分裂涉及到在正在分裂的細(xì)胞的赤道板上新的細(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。

)Cellwallmaterialisthendepositedintheregionofthecellplate.然后，細(xì)胞壁材料在細(xì)胞板區(qū)域沉積．11/6/2024ActinandMyosinandCytokinesisOperationoftheContractileRingduringCytokinesis11/6/2024

5.Meiosis:thebasisofsexualreproduction

減數(shù)分裂：有性生殖的基礎(chǔ)11/6/2024Meiosisisaspecialformofcelldivisionthattakesplaceinthereproductiveorgansthatproducesexcells.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。(減數(shù)分裂是性細(xì)胞分裂的特殊形式。

)Likemitosis,ittakesplaceafterDNAreplicationhasoccurredandinvolvestwosequentialnucleardivisions(meiosisIandmeiosisII).如有絲分裂，它也是發(fā)生在DNA復(fù)制后，并有兩個(gè)連續(xù)的核分裂。11/6/2024Thesedivisionresultsinfourdaughtercells,eachwithhalfthenumberofchromosomesoftheparentcell.減數(shù)分裂產(chǎn)生4個(gè)子細(xì)胞，分別含有親本一半的染色體數(shù)。Thephenomenonofcrossingoverduringmeiosisresultsinexchangeofgeneticinformationbetweenchromosomes.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。11/6/2024Hence,thehomologouschromosomedistributedtodifferentprogenycellsarenotidentical.因此，分配到不同子細(xì)胞中的同源染色體是不相同的。11/6/202411/6/2024AsinmitosistwochromatidsexistforeachchromosomeatthebeginningofprophaseI.正如在有絲分裂中一樣，在前期I開(kāi)始的時(shí)候每個(gè)染色體是以兩個(gè)染色單體形式存在．11/6/2024Duringthisphasethehomologouschromosomesundergosynapsis,orpairing,whichisbroughtaboutbyabridgingstructureofproteinsandRNAcalledthesynaptinemalcomplex.在這個(gè)時(shí)期，同源染色體通過(guò)蛋白質(zhì)和RNA組成的聯(lián)會(huì)復(fù)合體進(jìn)行聯(lián)會(huì)或配對(duì)。Thehomologouspairsstaytogetherwhentheyalignonthemetaphaseplate.同源染色體對(duì)一起成線形排列在中期赤道板上。

11/6/2024Unliketheanaphaseofmitosis,however,duringanaphaseIthetwochromatidsofeachchromosomestayjoinedatthecentromereandmovetogethertooneofthetwopolesofthecell.但是，與有絲分裂后期不同的是，在后期I，每組染色體的兩個(gè)染色單體連接在著絲點(diǎn)上并一起移向細(xì)胞兩極的一極。Itisthiseventthatresultsinthehalvingofthechromosomenumberinthefourdaughtercellsthatresultfrommeiosis.由此而導(dǎo)致4個(gè)子細(xì)胞中染色體數(shù)減半。11/6/2024DuringtelophaseInuclearenvelopesenclosethechromosomesinnuclei,andinmostspeciescytokinesis(thefirstnucleardivision)follows.在末期I，核被膜圍繞著細(xì)胞核里的染色體，在大多數(shù)物種里第一次胞質(zhì)分裂緊隨其后．

ThesecondnucleardivisionbeginswithmetaphaseII,inwhichthechromosomesineachdaughtercellagainalignonametaphaseplate．第二次核分裂開(kāi)始于分裂中期II

，子細(xì)胞中染色體再次重新排列在赤道板上。

11/6/2024Thecentromeresfinallydivide,andeachsisterchromatidmovestooneofthepolesofthespindle.著絲粒最終分離，每個(gè)姊妹染色單體移向兩極。ThenextphaseistelophaseII,followedagainbycytokinesis.下一個(gè)時(shí)期是末期II，緊接著是第二次胞質(zhì)分裂。

Theresultoftheentireprocessisfourhaploidcellsinwhichparentalchromosomesarerandomlydistributed.

整個(gè)減數(shù)分裂過(guò)程，產(chǎn)生4個(gè)親本染色體隨機(jī)分配的單倍體細(xì)胞。11/6/20246.Asexualversussexualreproduction

無(wú)性和有