连锁遗传及染色体作

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1、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)Linkageisthetendencyforallelesoftw

2、oormoregenestopassfromonegenerationtothenextinthesamecombination.Onlygenessituatedonthesamechromosomecanshowlinkage.Thatmeanstheclosertogetheranytwogeneslieonthesamechromosomethemorelinkagetheyaretoshowlinkageandthestrongerthatlinkagewillbe.连锁-两个或两个以上等位基因一起

3、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):Completelinkage同源染色体上的基因随其染色体一起进入到同一配子中去的遗传方式。4.1.2雌果蝇的

4、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presentedi

5、n1910byMorgan4.2Frequencyofcross-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%=0Thecloserthetwogenesaretogetherthelesslikelyitisthatacross-overwilltakeplacebetweenthem.Thefrequencyofr

6、ecombinantsgiveanindirectmeasureofhowclosethetwogeneslietoeachother.*发生交换的性母细胞比例为交换值的?倍单交换(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%recom

7、binationisequivalentto1mapunit.(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)F1CcShsh×无色、凹陷(ccshsh)C、Sh交换值3.6%3.6cM2.糯性、饱满(wxwxShSh)×非糯性、凹陷(WxWxshsh)F1Wx

8、wxShsh×糯性、凹陷(wxwxshsh)W、Sh交换值20%,20cM

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13、wxshc

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18、shcwx3.非糯性、有色