连锁遗传及染色体作图课件

Chapter4LinkageInheritanceandMappingGeneonChromosome

第四章连锁遗传及染色体作图4.1LawofLinkage(连锁规律)4.2Frequencyofcross-overs(交换值)4.3Mappinggeneonchromosomes(基因定位)4.4Interference（干涉）

4.5Linkageanalysisinfungi(真菌的连锁分析)4.1LawofLinkage(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。e.g.雄性果蝇的完全连锁遗传(测交后代表型与亲本完全一致,无新类型产生)：亲本灰身残翅(male)×黑身长翅(female)子一代灰身长翅(male)×黑身残翅(female)子代配子配子比1:1测交后代灰身残翅黑身长翅表型比1:1BvgBvgbVgbVgBvgbVgbvgbvgBvgbVgbvgBvgbvgbVgbvg4.1.1Completelinkage(完全连锁):4.1.2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%

BvgBvgbVgbVgBvgbVgbvgbvgBvgbVgbvgBvgbvgbVgbvgBVgbvgBVgbvgbvgbvgIncompletelinkage

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presentedin1910byMorgan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)4.3MappinggeneonchromosomeTwo-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:重组有色、饱满(CCShSh)×

无色、凹陷(ccshsh)F1

CcShsh×

无色、凹陷(ccshsh)C、Sh交换值3.6%3.6cM

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

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

wxshc

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

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

shcwx3.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?Three-factorcrosses(三点测验法):Thesearemoreaccuratethantwo-factorcrosses,inthattheyidentifyandutilizemanyofthedoublecross-oversthataremissedbytwo-factorcross.

PhenotypesGenotypesno.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=1334Frequencyofsinglecross-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Frequencyofdoublecross-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----------------ICShWxCoefficientofcoincidence（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7allelesMendalresearchedsituatedon7individualchromosome?

IIIIIIIVVVIVIIA/a-0I/i-204R/r-60Gp/gp-21V/v-211Le/le-199F/f-78Application:

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?

4.5Linkageanalysisinfungi(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

eg.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+m5m++m6m+m