第 章轉(zhuǎn)座子和逆轉(zhuǎn)座子課件

第11章轉(zhuǎn)座子和逆轉(zhuǎn)座子

TransposonsandretrotansposonsThesun1642tomatovarietyproducesanelongatedfruit,which

isproducedbyaduplicationthataroseasaresultofthepresenceofthetransposableelementRider.第11章轉(zhuǎn)座子和逆轉(zhuǎn)座子

Transposonsan1轉(zhuǎn)座子

(transposon,Tn)

基因組中可以從一個(gè)基因座轉(zhuǎn)移到另一個(gè)基因座，具有移動(dòng)能力的一段DNA片段。

ADNAsequencecapableofmoving(transposing)fromonelocationtoanotherinagenome.2轉(zhuǎn)座子(transposon,Tn)基因組中可以從一個(gè)2DiscoveryofTransposableElementsMcClintock’sexperimentsinmaize:theDselement

1940-19503轉(zhuǎn)座因子的發(fā)現(xiàn)DiscoveryofTransposableElem3印第安彩虹玉米，具有從最大到最小易于區(qū)分的10對染色體。解離因子

(Dissociation,Ds):locatedatthesiteofthebreak激活因子

(Activator,Ac)

:unlinkedgeneticfactor4印第安彩虹玉米，具有從最大到最小易于區(qū)分的10對染色體。解離4555

TransposableelementinE.coli

,

19606TransposableelementinE.c6轉(zhuǎn)座子的分類7非復(fù)制性的轉(zhuǎn)座（占已經(jīng)發(fā)現(xiàn)的多數(shù)）復(fù)制性逆轉(zhuǎn)座逆轉(zhuǎn)座病毒樣的轉(zhuǎn)座子轉(zhuǎn)座子的分類7非復(fù)制性的轉(zhuǎn)座復(fù)制性逆轉(zhuǎn)座逆轉(zhuǎn)座病毒樣的轉(zhuǎn)座子7第一節(jié)細(xì)菌的轉(zhuǎn)座因子TransposableelementsinBacteria

兩大類:簡單轉(zhuǎn)座因子：只包含和轉(zhuǎn)座有關(guān)的基因序列。Simpletransposableelements

whichcarryonlytheinformationrequiredformovement.復(fù)合轉(zhuǎn)座因子：除了含有與轉(zhuǎn)座相關(guān)的基因外還有其它基因（如抗生素抗性基因）。ComplextransposableelementswhichcontainDNAsequencesnotdirectlyrelatedtotransposition.8第一節(jié)細(xì)菌的轉(zhuǎn)座因子兩大類:881.插入序列

(Insertionsequences，IS)

9不含任何宿主基因的可轉(zhuǎn)位的DNA序列，是最簡單的轉(zhuǎn)座因子。1.插入序列(Insertionsequences，IS9插入序列的結(jié)構(gòu)ThestructureofISelement10插入序列的結(jié)構(gòu)101011正向重復(fù)序列反向重復(fù)序列11正向重復(fù)序列反向重復(fù)序列11121212插入序列末端兩重復(fù)序列高度相似但不完全相同。AnISelementendsinshortinvertedterminalrepeats;usuallythetwocopiesoftherepeatarecloselyrelatedratherthanidentical.插入序列的中間序列常具有編碼轉(zhuǎn)座酶的功能。ISelementscodeforthetransposase.插入序列轉(zhuǎn)座后常導(dǎo)致靶位點(diǎn)的重復(fù)。WhenanISelementtransposes,asequenceofhostDNAatthesiteofinsertionisduplicated.13插入序列特點(diǎn)：插入序列末端兩重復(fù)序列高度相似但不完全相同。13插入序列特點(diǎn)13DuplicationofashortsequenceofDNAattheinsertionsite14Duplicationofashortsequenc14TheISelementsarenormalconstituentsofbacterialchromosomesandplasmids.15TheISelementsarenormalcon15FormationofaconjugativeRplasmidbyrecombinationbetweenISelements16(Resistancetransferfactore,RTF)細(xì)菌耐藥性FormationofaconjugativeRp162.復(fù)合轉(zhuǎn)座子CompositeTransposons

CompositetransposonscontainavarietyofgenesthatresidebetweentwonearlyidenticalISelements.CompositetransposonisdesignatedbyTn,followedbyanumber.17四環(huán)素2.復(fù)合轉(zhuǎn)座子17四環(huán)素1718氯霉素四環(huán)素卡拉霉素18氯霉素四環(huán)素卡拉霉素18一些復(fù)合轉(zhuǎn)座子兩端的IS序列完全相同的，如Tn9和Tn903。Insomecases,ISmodulesareidentical,suchasTn9(directrepeatsofIS1)orTn903(invertedrepeatsofIS903).另外一些轉(zhuǎn)座子中，IS非常相似但不完全相同，因而用R和L表示。Inothercases,themodulesarecloselyrelated,butnotidentical.SowecandistinguishtheLandRmodulesinTn10orinTn5.復(fù)合轉(zhuǎn)座子特點(diǎn)：一些復(fù)合轉(zhuǎn)座子兩端的IS序列完全相同的，如Tn9和Tn90319Aschematicmapofaplasmidcarryingsimpleandcompositetransposon-resistancegenes.20Aschematicmapofaplasmidc20IS序列既可以自我轉(zhuǎn)座又可以和復(fù)合轉(zhuǎn)座子共同轉(zhuǎn)座。AfunctionalISmodulecantransposeeitheritselfortheentiretransposon.當(dāng)IS序列完全相同時(shí)，兩者均可獨(dú)立進(jìn)行轉(zhuǎn)座。WhenthetwoISmodulesareidentical,eithermodulecansponsorthetransposition.當(dāng)IS序列不完全相同時(shí)，兩者之一引發(fā)轉(zhuǎn)座，L。Whenthemodulesaredifferent,transpositioncandependononeofthemodulesIS序列既可以自我轉(zhuǎn)座又可以和復(fù)合轉(zhuǎn)座子共同轉(zhuǎn)座。213.非復(fù)合型轉(zhuǎn)座子Noncompositetransposons22轉(zhuǎn)座酶抑制酶氨芐青霉素抗性反向重復(fù)序列3.非復(fù)合型轉(zhuǎn)座子Noncompositetranspo2223共整合體23共整合體23第二節(jié)真核生物的轉(zhuǎn)座因子

TransposableElementsinEukaryotesDNA轉(zhuǎn)座子

(cutandpastetransposons)AcandDselementsinmaizePelementsinDrosophila反轉(zhuǎn)座子（Retrotransposons）24第二節(jié)真核生物的轉(zhuǎn)座因子

TransposableEl241.玉米的Ac-Ds轉(zhuǎn)座系統(tǒng)

（TheAc-Dssysteminmaize）BarbaraMcClintock(1902-1992)1940s~1950s1983NobelPrize251.玉米的Ac-Ds轉(zhuǎn)座系統(tǒng)

（Th2526Movie26Movie26玉米中轉(zhuǎn)座因子效應(yīng)27？玉米中轉(zhuǎn)座因子效應(yīng)27？27282828其它植物中的轉(zhuǎn)座因子Transposableelementinotherplantspeassnapdragons29SBE直鏈支鏈其它植物中的轉(zhuǎn)座因子peassnapdragons29SBE29雜交劣育（Hybriddysgenesis）:aconditioncausingsterility,elevatedmutationrate,andachromosomerearrangementintheoffspringofcrossesbetweencertainstrainsoffruitflies.

302.果蠅的P因子

PelementtransposonsinDrosophilia302.果蠅的P因子3031313132反向重復(fù)序列體細(xì)胞生殖細(xì)胞終止密碼子阻遏蛋白轉(zhuǎn)座酶32反向重體細(xì)胞生殖細(xì)胞終止密碼子阻遏蛋白轉(zhuǎn)座酶3266KD的轉(zhuǎn)座阻遏蛋白是造成現(xiàn)象差異的主要原因。（The66KDrepressorproteinisprovidedasamaternalfactorintheegg）3366KD的轉(zhuǎn)座阻遏蛋白是造成現(xiàn)象差異的主要原因。（Th33P-element-mediatedgenetransferinDrosophila34P-element-mediatedgene34343.反轉(zhuǎn)錄病毒與反轉(zhuǎn)座子

RetrovirusesandRetroposons

反轉(zhuǎn)錄病毒：單鏈的RNA病毒，依靠獨(dú)立的雙鏈DNA中間體結(jié)構(gòu)進(jìn)行感染。Retroviruses

aresingle-strandedRNAanimalvirusesthatemployadouble-strandedDNAintermediateforreplication.353.反轉(zhuǎn)錄病毒與反轉(zhuǎn)座子

Retroviruses35363636※Thelifecycleofaretrovirus※37※Thelifecycleofaretroviru37Thetypicalgenomeofaretroviruscontainsgag,pol,andenvgenes逆轉(zhuǎn)錄病毒基因表達(dá)38菱形衣殼蛋白外殼蛋白逆轉(zhuǎn)錄酶病毒側(cè)翼序列Thetypicalgenomeofaretrov38逆轉(zhuǎn)錄病毒可隨機(jī)整合到宿主細(xì)胞。TheviralDNAintegratesintothehostgenomeatrandomlyselectedsites.有時(shí)（幾率較?。┠孓D(zhuǎn)錄病毒可能將宿主細(xì)胞轉(zhuǎn)化為腫瘤細(xì)胞。Sometimes(probablyratherrarely),theintegratedretroviruscanconvertahostcellintoatumorigenicstatethroughactivatingcertaintypesofhostgenes.39逆轉(zhuǎn)錄病毒可隨機(jī)整合到宿主細(xì)胞。393940啟動(dòng)子增強(qiáng)子40啟動(dòng)子40逆轉(zhuǎn)座子（Retroposon）

逆轉(zhuǎn)錄轉(zhuǎn)座子指通過RNA為中介,反轉(zhuǎn)錄成DNA后進(jìn)行轉(zhuǎn)座的轉(zhuǎn)座因子。逆轉(zhuǎn)座作用出現(xiàn)在真核生物。

（TransposableelementsthatutilizereversetranscriptasetotransposethroughanRNAintermediatearetermedretrotransposons.）退化的逆病毒逆轉(zhuǎn)座子（Retroposon）逆轉(zhuǎn)錄轉(zhuǎn)座子指41424242

逆轉(zhuǎn)座子在真核生物中可分為兩類：

病毒樣逆轉(zhuǎn)座子

(Viralretrotransposons):

與反轉(zhuǎn)錄病毒結(jié)構(gòu)類似，不同之處在于不形成病毒顆粒。

如YeastTyelements,Drosophila

copia

elements

非病毒樣逆轉(zhuǎn)座子

(Nonviralretrotransposons)

:

不形成逆轉(zhuǎn)錄酶和整合酶，依靠外源提供的轉(zhuǎn)座酶，真核生物基因組中所占比例最高。

LINEs(longinterspersedelements)and

SINEs

inmammals43逆轉(zhuǎn)座子在真核生物中可分為兩類：4343病毒與真核生物基因組中逆轉(zhuǎn)座子結(jié)構(gòu)比較44鼠白血病毒病毒與真核生物基因組中逆轉(zhuǎn)座子結(jié)構(gòu)比較44鼠白血病毒44酵母TY系列（YeastTyelements）About35Ty1copiesintheyeastgenome.

δsequences:330bp,about100copies.

soloδelement.45酵母TY系列（YeastTyelements）Abo45**3.Basesubstitutionformarkingoneδ

TranspositionthroughanRNAintermediate462.半乳糖誘導(dǎo)啟動(dòng)子1實(shí)驗(yàn)證明：**3.Basesubstitutionformark46Drosophila

copiaelements47Drosophilacopiaelements4747轉(zhuǎn)座因子的頻率不同的轉(zhuǎn)座因子的轉(zhuǎn)座頻率不同。每個(gè)世代轉(zhuǎn)座頻率約為10-3~10-4

。Newgerm-linetranspositionsareestimatedtooccuronceinevery50to100humanbirths.每個(gè)世代中轉(zhuǎn)座插入靶位點(diǎn)使某個(gè)基因所引起的突變和自發(fā)突變概率相當(dāng)，約為10-5~

10-7

。48第三節(jié)轉(zhuǎn)座的遺傳學(xué)效應(yīng)

Geneticeffectoftransposition轉(zhuǎn)座因子的頻率不同的轉(zhuǎn)座因子的轉(zhuǎn)座頻率不同。48第三節(jié)轉(zhuǎn)4849TransposableelementsasgeneticparasitesReplicationandspreadofTesmayservenopurposeforthecell.TheinsertionofTesintoagenewilloftendestroyitsfunction,withharmfulconsequencesforthecell.ThetimeandenergyrequiretoreplicatelargenumbersofTesarelikelytoplaceametabolicburdenonthecell.49Transposableelementsasgen49人類中的轉(zhuǎn)座子50人類中的轉(zhuǎn)座子5050Repetitiveelementsfoundinthehumangene(HGO)codingforhomogentisate1,2-dioxygenase(尿黑酸-1,2-氧化酶),theenzymewhosedeficiencycausesalkaptonuria（尿黑酸尿）.TheAlusequencesmakeupmorethan10%ofthehumangenome.51Repetitiveelementsfoundint51Transposableelementsingrassesareresponsibleforgenomesizedifferences其它生物中的轉(zhuǎn)座因子Green:transposons;Orange:genes52Transposableelementsingrass52轉(zhuǎn)座因子引起的遺傳效應(yīng)基因突變（編碼區(qū)）染色體結(jié)構(gòu)改變（非編碼區(qū)）轉(zhuǎn)座因子引起的遺傳效應(yīng)基因突變（編碼區(qū)）53TransposobleelementcangeneratemutationsinadjacentgenesAbout50%ofallspontaneousmutationsinDrosophilaareduetotransposition,10%(mouse),0.2%(human).54Transposobleelementcangener54Retrotransposon-InducedMutationsinGrapeSkinColorSCIENCE,14MAY2004,VOL30455Retrotransposon-InducedSCIENCE55Transposableelementscancauserearrangementsofthegenomedeletioninversion56Transposableelementscancaus56Relocategenes57Relocategenes5757EvolutionarySignificanceofTransposableElements轉(zhuǎn)座子的馴化Transposase(轉(zhuǎn)座酶)regulateplantgenesinArabidopsisTelomeraseandreversetranscriptase（果蠅）

58EvolutionarySignificanceofT58HowdoplantsandanimalssurviveandthrivewithsomanyinsertionsingenesandsomuchmobileDNAinthegenome?安全島（safeheavens）多拷貝基因（基因組較小的生物）宿主細(xì)胞表觀遺傳調(diào)控宿主與轉(zhuǎn)座因子在細(xì)胞內(nèi)處于不斷博弈過程中。59Howdoplantsandanimalssurv59思考題：1、結(jié)合所學(xué)的知識，試分析一些致病菌極易產(chǎn)生抗藥性的原因？2、試分析生物是如何避免基因組中轉(zhuǎn)座行為所引起有害突變的。思考題：1、結(jié)合所學(xué)的知識，試分析一些致病菌極易產(chǎn)生抗藥性的60第11章轉(zhuǎn)座子和逆轉(zhuǎn)座子

TransposonsandretrotansposonsThesun1642tomatovarietyproducesanelongatedfruit,which

isproducedbyaduplicationthataroseasaresultofthepresenceofthetransposableelementRider.第11章轉(zhuǎn)座子和逆轉(zhuǎn)座子

Transposonsan61轉(zhuǎn)座子

(transposon,Tn)

基因組中可以從一個(gè)基因座轉(zhuǎn)移到另一個(gè)基因座，具有移動(dòng)能力的一段DNA片段。

ADNAsequencecapableofmoving(transposing)fromonelocationtoanotherinagenome.62轉(zhuǎn)座子(transposon,Tn)基因組中可以從一個(gè)62DiscoveryofTransposableElementsMcClintock’sexperimentsinmaize:theDselement

1940-195063轉(zhuǎn)座因子的發(fā)現(xiàn)DiscoveryofTransposableElem63印第安彩虹玉米，具有從最大到最小易于區(qū)分的10對染色體。解離因子

(Dissociation,Ds):locatedatthesiteofthebreak激活因子

(Activator,Ac)

:unlinkedgeneticfactor64印第安彩虹玉米，具有從最大到最小易于區(qū)分的10對染色體。解離6465565

TransposableelementinE.coli

,

196066TransposableelementinE.c66轉(zhuǎn)座子的分類67非復(fù)制性的轉(zhuǎn)座（占已經(jīng)發(fā)現(xiàn)的多數(shù)）復(fù)制性逆轉(zhuǎn)座逆轉(zhuǎn)座病毒樣的轉(zhuǎn)座子轉(zhuǎn)座子的分類7非復(fù)制性的轉(zhuǎn)座復(fù)制性逆轉(zhuǎn)座逆轉(zhuǎn)座病毒樣的轉(zhuǎn)座子67第一節(jié)細(xì)菌的轉(zhuǎn)座因子TransposableelementsinBacteria

兩大類:簡單轉(zhuǎn)座因子：只包含和轉(zhuǎn)座有關(guān)的基因序列。Simpletransposableelements

whichcarryonlytheinformationrequiredformovement.復(fù)合轉(zhuǎn)座因子：除了含有與轉(zhuǎn)座相關(guān)的基因外還有其它基因（如抗生素抗性基因）。ComplextransposableelementswhichcontainDNAsequencesnotdirectlyrelatedtotransposition.68第一節(jié)細(xì)菌的轉(zhuǎn)座因子兩大類:8681.插入序列

(Insertionsequences，IS)

69不含任何宿主基因的可轉(zhuǎn)位的DNA序列，是最簡單的轉(zhuǎn)座因子。1.插入序列(Insertionsequences，IS69插入序列的結(jié)構(gòu)ThestructureofISelement70插入序列的結(jié)構(gòu)107071正向重復(fù)序列反向重復(fù)序列11正向重復(fù)序列反向重復(fù)序列71721272插入序列末端兩重復(fù)序列高度相似但不完全相同。AnISelementendsinshortinvertedterminalrepeats;usuallythetwocopiesoftherepeatarecloselyrelatedratherthanidentical.插入序列的中間序列常具有編碼轉(zhuǎn)座酶的功能。ISelementscodeforthetransposase.插入序列轉(zhuǎn)座后常導(dǎo)致靶位點(diǎn)的重復(fù)。WhenanISelementtransposes,asequenceofhostDNAatthesiteofinsertionisduplicated.73插入序列特點(diǎn)：插入序列末端兩重復(fù)序列高度相似但不完全相同。13插入序列特點(diǎn)73DuplicationofashortsequenceofDNAattheinsertionsite74Duplicationofashortsequenc74TheISelementsarenormalconstituentsofbacterialchromosomesandplasmids.75TheISelementsarenormalcon75FormationofaconjugativeRplasmidbyrecombinationbetweenISelements76(Resistancetransferfactore,RTF)細(xì)菌耐藥性FormationofaconjugativeRp762.復(fù)合轉(zhuǎn)座子CompositeTransposons

CompositetransposonscontainavarietyofgenesthatresidebetweentwonearlyidenticalISelements.CompositetransposonisdesignatedbyTn,followedbyanumber.77四環(huán)素2.復(fù)合轉(zhuǎn)座子17四環(huán)素7778氯霉素四環(huán)素卡拉霉素18氯霉素四環(huán)素卡拉霉素78一些復(fù)合轉(zhuǎn)座子兩端的IS序列完全相同的，如Tn9和Tn903。Insomecases,ISmodulesareidentical,suchasTn9(directrepeatsofIS1)orTn903(invertedrepeatsofIS903).另外一些轉(zhuǎn)座子中，IS非常相似但不完全相同，因而用R和L表示。Inothercases,themodulesarecloselyrelated,butnotidentical.SowecandistinguishtheLandRmodulesinTn10orinTn5.復(fù)合轉(zhuǎn)座子特點(diǎn)：一些復(fù)合轉(zhuǎn)座子兩端的IS序列完全相同的，如Tn9和Tn90379Aschematicmapofaplasmidcarryingsimpleandcompositetransposon-resistancegenes.80Aschematicmapofaplasmidc80IS序列既可以自我轉(zhuǎn)座又可以和復(fù)合轉(zhuǎn)座子共同轉(zhuǎn)座。AfunctionalISmodulecantransposeeitheritselfortheentiretransposon.當(dāng)IS序列完全相同時(shí)，兩者均可獨(dú)立進(jìn)行轉(zhuǎn)座。WhenthetwoISmodulesareidentical,eithermodulecansponsorthetransposition.當(dāng)IS序列不完全相同時(shí)，兩者之一引發(fā)轉(zhuǎn)座，L。Whenthemodulesaredifferent,transpositioncandependononeofthemodulesIS序列既可以自我轉(zhuǎn)座又可以和復(fù)合轉(zhuǎn)座子共同轉(zhuǎn)座。813.非復(fù)合型轉(zhuǎn)座子Noncompositetransposons82轉(zhuǎn)座酶抑制酶氨芐青霉素抗性反向重復(fù)序列3.非復(fù)合型轉(zhuǎn)座子Noncompositetranspo8283共整合體23共整合體83第二節(jié)真核生物的轉(zhuǎn)座因子

TransposableElementsinEukaryotesDNA轉(zhuǎn)座子

(cutandpastetransposons)AcandDselementsinmaizePelementsinDrosophila反轉(zhuǎn)座子（Retrotransposons）84第二節(jié)真核生物的轉(zhuǎn)座因子

TransposableEl841.玉米的Ac-Ds轉(zhuǎn)座系統(tǒng)

（TheAc-Dssysteminmaize）BarbaraMcClintock(1902-1992)1940s~1950s1983NobelPrize851.玉米的Ac-Ds轉(zhuǎn)座系統(tǒng)

（Th8586Movie26Movie86玉米中轉(zhuǎn)座因子效應(yīng)87？玉米中轉(zhuǎn)座因子效應(yīng)27？87882888其它植物中的轉(zhuǎn)座因子Transposableelementinotherplantspeassnapdragons89SBE直鏈支鏈其它植物中的轉(zhuǎn)座因子peassnapdragons29SBE89雜交劣育（Hybriddysgenesis）:aconditioncausingsterility,elevatedmutationrate,andachromosomerearrangementintheoffspringofcrossesbetweencertainstrainsoffruitflies.

902.果蠅的P因子

PelementtransposonsinDrosophilia302.果蠅的P因子9091319192反向重復(fù)序列體細(xì)胞生殖細(xì)胞終止密碼子阻遏蛋白轉(zhuǎn)座酶32反向重體細(xì)胞生殖細(xì)胞終止密碼子阻遏蛋白轉(zhuǎn)座酶9266KD的轉(zhuǎn)座阻遏蛋白是造成現(xiàn)象差異的主要原因。（The66KDrepressorproteinisprovidedasamaternalfactorintheegg）9366KD的轉(zhuǎn)座阻遏蛋白是造成現(xiàn)象差異的主要原因。（Th93P-element-mediatedgenetransferinDrosophila94P-element-mediatedgene34943.反轉(zhuǎn)錄病毒與反轉(zhuǎn)座子

RetrovirusesandRetroposons

反轉(zhuǎn)錄病毒：單鏈的RNA病毒，依靠獨(dú)立的雙鏈DNA中間體結(jié)構(gòu)進(jìn)行感染。Retroviruses

aresingle-strandedRNAanimalvirusesthatemployadouble-strandedDNAintermediateforreplication.953.反轉(zhuǎn)錄病毒與反轉(zhuǎn)座子

Retroviruses95963696※Thelifecycleofaretrovirus※97※Thelifecycleofaretroviru97Thetypicalgenomeofaretroviruscontainsgag,pol,andenvgenes逆轉(zhuǎn)錄病毒基因表達(dá)98菱形衣殼蛋白外殼蛋白逆轉(zhuǎn)錄酶病毒側(cè)翼序列Thetypicalgenomeofaretrov98逆轉(zhuǎn)錄病毒可隨機(jī)整合到宿主細(xì)胞。TheviralDNAintegratesintothehostgenomeatrandomlyselectedsites.有時(shí)（幾率較小）逆轉(zhuǎn)錄病毒可能將宿主細(xì)胞轉(zhuǎn)化為腫瘤細(xì)胞。Sometimes(probablyratherrarely),theintegratedretroviruscanconvertahostcellintoatumorigenicstatethroughactivatingcertaintypesofhostgenes.99逆轉(zhuǎn)錄病毒可隨機(jī)整合到宿主細(xì)胞。3999100啟動(dòng)子增強(qiáng)子40啟動(dòng)子100逆轉(zhuǎn)座子（Retroposon）

逆轉(zhuǎn)錄轉(zhuǎn)座子指通過RNA為中介,反轉(zhuǎn)錄成DNA后進(jìn)行轉(zhuǎn)座的轉(zhuǎn)座因子。逆轉(zhuǎn)座作用出現(xiàn)在真核生物。

（TransposableelementsthatutilizereversetranscriptasetotransposethroughanRNAintermediatearetermedretrotransposons.）退化的逆病毒逆轉(zhuǎn)座子（Retroposon）逆轉(zhuǎn)錄轉(zhuǎn)座子指10110242102

逆轉(zhuǎn)座子在真核生物中可分為兩類：

病毒樣逆轉(zhuǎn)座子

(Viralretrotransposons):

與反轉(zhuǎn)錄病毒結(jié)構(gòu)類似，不同之處在于不形成病毒顆粒。

如YeastTyelements,Drosophila

copia

elements

非病毒樣逆轉(zhuǎn)座子

(Nonviralretrotransposons)

:

不形成逆轉(zhuǎn)錄酶和整合酶，依靠外源提供的轉(zhuǎn)座酶，真核生物基因組中所占比例最高。

LINEs(longinterspersedelements)and

SINEs

inmammals103逆轉(zhuǎn)座子在真核生物中可分為兩類：43103病毒與真核生物基因組中逆轉(zhuǎn)座子結(jié)構(gòu)比較104鼠白血病毒病毒與真核生物基因組中逆轉(zhuǎn)座子結(jié)構(gòu)比較44鼠白血病毒104酵母TY系列（YeastTyelements）About35Ty1copiesintheyeastgenome.

δsequences:330bp,about100copies.

soloδelement.105酵母TY系列（YeastTyelements）Abo105**3.Basesubstitutionformarkingoneδ

TranspositionthroughanRNAintermediate1062.半乳糖誘導(dǎo)啟動(dòng)子1實(shí)驗(yàn)證明：**3.Basesubstitutionformark106Drosophila

copiaelements107Drosophilacopiaelements47107轉(zhuǎn)座因子的頻率不同的轉(zhuǎn)座因子的轉(zhuǎn)座頻率不同。每個(gè)世代轉(zhuǎn)座頻率約為10-3~10-4

。Newgerm-linetranspositionsareestimatedtooccuronceinevery50to100humanbirths.每個(gè)世代中轉(zhuǎn)座插入靶位點(diǎn)使某個(gè)基因所引起的突變和自發(fā)突變概率相當(dāng)，約為10-5~

10-7

。108第三節(jié)轉(zhuǎn)座的遺傳學(xué)效應(yīng)

Geneticeffectoftransposition轉(zhuǎn)座因子的頻率不同的轉(zhuǎn)座因子的轉(zhuǎn)座頻率不同。48第三節(jié)轉(zhuǎn)108109TransposableelementsasgeneticparasitesReplicationandspreadofTesmayservenopurposeforthecell.TheinsertionofTesintoagenewilloftendestroyitsfunction,