连锁遗传及染色体作图课件

连锁遗传及染色体作图连锁遗传及染色体作图14.1LawofLinkage(连锁规律)Linkageisthetendencyforallelesoftwoormoregenestopassfromonegenerationtothenextinthesamecombination.Onlygenessituatedonthesamechromosomecanshowlinkage.Thatmeanstheclosertogetheranytwogeneslieonthesamechromosomethemorelinkagetheyaretoshowlinkageandthestrongerthatlinkagewillbe.连锁-两个或两个以上等位基因一起从一代传递到下一代的现象。4.1LawofLinkage(连锁规律)Linka2连锁遗传及染色体作图课件3连锁遗传及染色体作图课件44.1.2雌果蝇的不完全连锁遗传(incompletelinkage)：亲本灰身残翅(male)×黑身长翅(female)子一代灰身长翅(female)×黑身残翅(male)子代配子配子比两两相等测交后代

灰身残翅灰身长翅黑身残翅黑身长翅亲本型83%

41.5%8.5%8.5%41.5%交换型17%

BvgBvgbVgbVgBvgbVgbvgbvgBvgbVgbvgBvgbvgbVgbvgBVgbvgBVgbvgbvgbvg4.1.2雌果蝇的不完全连锁遗传(incomplete5连锁遗传及染色体作图课件6Incompletelinkage

同源染色体上的基因既有连锁又有交换的遗传现象—

连锁互换律presentedin1910byMorganIncompletelinkage74.2Frequencyofcross-overs(交换值)Frequencyofcross-overs={重组配子数(交换型配子数)/总配子数(交换型+亲本型)}×100%=(No.ofrecombinant/Totalno.ofprogeny)×100%=50%=0~50%=0

Thecloserthetwogenesaretogetherthelesslikelyitisthatacross-overwilltakeplacebetweenthem.Thefrequencyofrecombinantsgiveanindirectmeasureofhowclosethetwogeneslietoeachother.*发生交换的性母细胞比例为交换值的?倍4.2Frequencyofcross-overs(8单交换(singlecross-overs)：基因间分别发生单个交换双交换(doublecross-overs)：同源染色体上的等位基因间同时发生两次单交换。图距：Iftherecombinationfrequencyis14%,theyhaveamapdistanceof14mapunits(图距)betweenthem.1%recombinationisequivalentto1mapunit.(1%的重组率等于1个图距)4.3Mappinggeneonchromosome单交换(singlecross-overs)：基因间分别发9Two-factorcrosses(两点测验法)

eg.Maize:有色C/无色c饱满Sh/凹陷sh非糯性Wx/糯性wxCrossesaresetoutbelow:Two-factorcrosses(两点测验法)10重组有色、饱满(CCShSh)×无色、凹陷(ccshsh)F1CcShsh×

无色、凹陷(ccshsh)C、Sh交换值3.6%3.6cM重组有色、饱满(CCShSh)×112.糯性、饱满(wxwxShSh)×非糯性、凹陷(WxWxshsh)F1WxwxShsh×糯性、凹陷(wxwxshsh)W、Sh交换值20%,20cM2.糯性、饱满(wxwxShSh)×非糯性、凹陷(WxW12

|-------------23.6-----------------------|

|----------------20----------|----3.6----|

wxshc

|-------------20------------|

|-----3.6----|----16.4------|

shcwx|-------------23.6-----------133.非糯性、有色(WxWxCC)×糯性、无色(wxwxcc)F1WxwxCc×糯性、无色(wxwxcc)W、C交换值22%，22cM两值为什么不完全一致?3.非糯性、有色(WxWxCC)×糯性、无色(wxwx14Three-factorcrosses(三点测验法):Thesearemoreaccuratethantwo-factorcrosses,inthattheyidentifyandutilizemanyofthedoublecross-oversthataremissedbytwo-factorcross.

Three-factorcrosses(三点测验法):15

P有色、饱满、非糯(++++++)×无色、皱缩、糯性(ccshshwxwx)

F1有色、饱满、非糯(+c+sh+wx)×无色、皱缩、糯性(ccshshwxwx)P有色、饱满、非糯(++++++)16PhenotypesGenotypesno.ofF2assembledtypes有色、饱满、非糯+++2238parental无色、皱缩、糯性cshwx2198无色、饱满、非糯c++98single有色、皱缩、糯性+shwx107cross-oversⅠ有色、饱满、糯性++wx672single无色、皱缩、非糯csh+662cross-oversⅡ无色、饱满、糯性c+wx39double有色、皱缩、非糯+sh+19cross-oversTotalno.ofF26033no.ofF2fromdoublecross-overs：39+19=58;no.ofF2fromsinglecross-oversI:98+107=205;no.ofF2fromsinglecross-oversII:672+662=1334Phenotypes17Frequencyofsinglecross-overs={(no.ofsinglecross-overs+no.ofdoublecross-overs)/totalno.ofprogeny}×100%

单交换值=(单交换个体数+双交换个体数）/总数×100%=单交换值I+双交换值Frequencyofsinglecross-over18Frequencyofdoublecross-overs(双交换值)=(39+19)/6033×100%=0.96%Frequencyofsinglecross-oversI(单交换Ⅰ交换值)=(98+107)/6033×100%+0.96%=3.4%+0.96%=4.36%Frequencyofsinglecross-oversII(单交换Ⅱ交换值)

=(672+662)/6033×100%+0.96%=22.11%+0.96%=23.07%MapunitofC、Sh:4.36cM，Sh、Wx:23.07cM

I-------------------27.43-----------------------------II-----4.36-----I----------------23.07----------------ICShWxFrequencyofdoublecross-over194.4Interference（干涉）：

交换在交叉处发生，一个单交换的发生，会影响另一个单交换的发生，即干涉。双交换理论值=单交换值Ⅰ×单交换值Ⅱ=4.36%×23.7%=1%Thepresenseofonechiasmatainaparticularchromosomeregioncanreducethefrequencyofothersformingclosetoit.Thiscanresultinareductioninthenumberofdoublecross-oversobserved.双交换实际值≠双交换理论值时表明两个单交换间有干涉4.4Interference（干涉）：20Coefficientofcoincidence（并发系数S）：

Theextentofinterferenceiscalculatedasthecoefficientofcoincidence,theobservednumberofdoublecross-oversdividedbytheexpectednumberofdoublecross-overs.

并发系数S=实际双交换值/理论双交换值=0~1S，干涉；=1,singlecross-oversindependently,nointerference;=0,completeinterference,nodoublecross-overs.1-S=干扰值Coefficientofcoincidence（并发217allelesMendalresearchedsituatedon7individualchromosome?

7allelesMendalresearched22IIIIIIIVVVIVIIA/a-0I/i-204R/r-60Gp/gp-21V/v-211Le/le-199F/f-78IIIIII23基因连锁群：

同一染色体上基因处同一连锁群，同类生物有n对染色体就有n个连锁群。e.g.Tomato2n=2412linkagegroupsDrosophila2n=84linkagegroups基因连锁群：24Application:

大麦(barley)高竿(B)/矮竿(b)，抗条锈病(T)/不抗条锈病(t)BT/BT×bt/bt两对基因连锁遗传，交换值为12%。如何在F2代获得3-4株纯种矮竿抗病单株?

Application:254.5Linkageanalysisinfungi(真菌的连锁分析):

Ascomycete(粗糙链孢霉):Monoploidandsexualreproduction

-Goodmaterialforgeneticanalysis

Tetradanalysis(四分体分析):减数分裂形成的四个线性排列的子囊孢子(orderedtetrad)的分析

p112,p144

4.5Linkageanalysisinfungi26决定孢子颜色的基因和着丝粒间没有发生交换，被称为第一种分裂分离(4:4的线性比)p112决定孢子颜色的基因和着丝粒之间发生了交换，两种颜色表型在第二次减数分裂时被分开，出现其他分离类型，称为第二种分裂分离(2:2:2:2或2:4:2线性比)子囊中仅一半的孢子发生重组.p113

Inascomycetefungi,firstandseconddivisionsegregationpatternscanbeusedtodeterminedistancebetweenageneandthecentromere.Asimilarapproachcanbeusedtoestimatedistancesbetweengenes.决定孢子颜色的基因和着丝粒间没有发生交换，被称为第一种分裂分27Recombinantfrequencybetweengeneandcentromere=(no.ofrecombinantascus/totalno.ofascus)×100%×½基因与着丝粒的重组率=交换型子囊数×100%×1/2总子囊数Recombinantfrequencybetween28eg.1甲硫氨酸（-）的链孢霉菌株(m)与野生型(+)菌株杂交，基因与着丝粒间距多远?做图表示交换型子囊产生过程?

子囊数孢子

1+23+45+67+86+m+m