連鎖遺傳及染色體作圖課件

Chapter4LinkageInheritanceandMappingGeneonChromosome

第四章連鎖遺傳及染色體作圖4.1LawofLinkage(連鎖規(guī)律)4.2Frequencyofcross-overs(交換值)4.3Mappinggeneonchromosomes(基因定位)4.4Interference（干涉）

4.5Linkageanalysisinfungi(真菌的連鎖分析)4.1LawofLinkage(連鎖規(guī)律)Linkageisthetendencyforallelesoftwoormoregenestopassfromonegenerationtothenextinthesamecombination.Onlygenessituatedonthesamechromosomecanshowlinkage.Thatmeanstheclosertogetheranytwogeneslieonthesamechromosomethemorelinkagetheyaretoshowlinkageandthestrongerthatlinkagewillbe.連鎖-兩個或兩個以上等位基因一起從一代傳遞到下一代的現(xiàn)象。e.g.雄性果蠅的完全連鎖遺傳(測交后代表型與親本完全一致,無新類型產(chǎn)生)：親本灰身殘翅(male)×黑身長翅(female)子一代灰身長翅(male)×黑身殘翅(female)子代配子配子比1:1測交后代灰身殘翅黑身長翅表型比1:1BvgBvgbVgbVgBvgbVgbvgbvgBvgbVgbvgBvgbvgbVgbvg4.1.1Completelinkage(完全連鎖):4.1.2雌果蠅的不完全連鎖遺傳(incompletelinkage)：親本灰身殘翅(male)×黑身長翅(female)子一代灰身長翅(female)×黑身殘翅(male)子代配子配子比兩兩相等測交后代

灰身殘翅灰身長翅黑身殘翅黑身長翅親本型83%

41.5%8.5%8.5%41.5%交換型17%

BvgBvgbVgbVgBvgbVgbvgbvgBvgbVgbvgBvgbvgbVgbvgBVgbvgBVgbvgbvgbvgIncompletelinkage

同源染色體上的基因既有連鎖又有交換的遺傳現(xiàn)象—

連鎖互換律presentedin1910byMorgan單交換(singlecross-overs)：基因間分別發(fā)生單個交換雙交換(doublecross-overs)：同源染色體上的等位基因間同時發(fā)生兩次單交換。圖距：Iftherecombinationfrequencyis14%,theyhaveamapdistanceof14mapunits(圖距)betweenthem.1%recombinationisequivalentto1mapunit.(1%的重組率等于1個圖距)4.3MappinggeneonchromosomeTwo-factorcrosses(兩點測驗法)

eg.Maize:有色C/無色c飽滿Sh/凹陷sh非糯性Wx/糯性wxCrossesaresetoutbelow:重組有色、飽滿(CCShSh)×

無色、凹陷(ccshsh)F1

CcShsh×

無色、凹陷(ccshsh)C、Sh交換值3.6%3.6cM

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

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

wxshc

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

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

shcwx3.非糯性、有色(WxWxCC)×糯性、無色(wxwxcc)F1WxwxCc×糯性、無色(wxwxcc)W、C交換值22%，22cM兩值為什么不完全一致?Three-factorcrosses(三點測驗法):Thesearemoreaccuratethantwo-factorcrosses,inthattheyidentifyandutilizemanyofthedoublecross-oversthataremissedbytwo-factorcross.

PhenotypesGenotypesno.ofF2assembledtypes有色、飽滿、非糯+++2238parental無色、皺縮、糯性cshwx2198無色、飽滿、非糯c++98single有色、皺縮、糯性+shwx107cross-oversⅠ有色、飽滿、糯性++wx672single無色、皺縮、非糯csh+662cross-oversⅡ無色、飽滿、糯性c+wx39double有色、皺縮、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%

單交換值=(單交換個體數(shù)+雙交換個體數(shù)）/總數(shù)×100%=單交換值I+雙交換值Frequencyofdoublecross-overs(雙交換值)=(39+19)/6033×100%=0.96%Frequencyofsinglecross-oversI(單交換Ⅰ交換值)=(98+107)/6033×100%+0.96%=3.4%+0.96%=4.36%Frequencyofsinglecross-oversII(單交換Ⅱ交換值)

=(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（并發(fā)系數(shù)S）：

Theextentofinterferenceiscalculatedasthecoefficientofcoincidence,theobservednumberofdoublecross-oversdividedbytheexpectednumberofdoublecross-overs.

并發(fā)系數(shù)S=實際雙交換值/理論雙交換值=0~1S，干涉；=1,singlecross-oversindependently,nointerference;=0,completeinterference,nodoublecross-overs.1-S=干擾值7allelesMendalresearchedsituatedon7individualchromosome?

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

大麥(barley)高竿(B)/矮竿(b)，抗條銹病(T)/不抗條銹病(t)BT/BT×bt/bt兩對基因連鎖遺傳，交換值為12%。如何在F2代獲得3-4株純種矮竿抗病單株?

4.5Linkageanalysisinfungi(真菌的連鎖分析):

Ascomycete(粗糙鏈孢霉):Monoploidandsexualreproduction

-Goodmaterialforgeneticanalysis

Tetradanalysis(四分體分析):減數(shù)分裂形成的四個線性排列的子囊孢子(orderedtetrad)的分析

p112,p144

eg.1甲硫氨酸（-）的鏈孢霉菌株(m)與野生型(+)菌株雜交，基因與著絲粒間距多遠?做圖表示交換型子囊產(chǎn)生過程?

子囊數(shù)孢子

1+23+45+67+86+m+m5m++m6m+m