连锁遗传及工染色体作图.pptVIP

Chapter 4 Linkage Inheritance and Mapping Gene on Chromosome 第四章 连锁遗传及染色体作图;4.1 Law of Linkage (连锁规律);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)：;Complete linkage 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 雌果蝇的不完全连锁遗传 (incomplete linkage)：;庭充督肆虞返炮尤芦揉爽隙琢艺樟台慕芯饥莉寇翘雇靖齿刚贝鳞吼剃芦涝连锁遗传及染色体作图连锁遗传及染色体作图;Incomplete linkage 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 presented in 1910 by Morgan ;4.2 Frequency of cross-overs (交换值) Frequency of cross-overs ={重组配子数(交换型配子数) / 总配子数(交换型+亲本型)}×100% = (No. of recombinant / Total no. of progeny) ×100% = 50% = 0 ~ 50% = 0 The closer the two genes are together the less likely it is that a cross-over will take place between them. The frequency of recombinants give an indirect measure of how close the two genes lie to each other. * 发生交换的性母细胞比例为交换值的?倍;单交换(single cross-overs)：基因间分别发生单个交换 双交换(double cross-overs)：同源染色体上的等位基因间同时发生两次单交换。;Two-factor crosses (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wx Crosses are set out below:;重组;2. 糯性、饱满(wxwxShSh) ×非糯性、凹陷(WxWxshsh) F1 WxwxShsh × 糯性、凹陷 (wxwxshsh) W、Sh交换值20%, 20 cM; |-------------23.6-----------------------|?|----------------20----------|----3.6----|wx sh c ;3. 非糯性、有色(WxWxCC) × 糯性、无色(wxwxcc) F1 WxwxCc × 糯性、无色(wxwxcc) W、C 交换值22%，22cM 两值为什么不完全一致?;Three-factor crosses (三点测验法): These are more accurate than two-factor crosses, in that they identify and utilize many of the double cross-overs that are missed by two-factor cross. ; P 有色、饱满、非糯 (++ ++ ++ ) × 无色、皱缩、糯性(cc shsh wxwx)　 F1 有色、饱满、非糯 (+c +sh +wx) × 无色、皱缩、糯性(cc shsh wxwx);Phenotypes Genotypes no. of F2 assembled types 有色、饱满、非