亲本杂交bprX+ b pr 摩尔根的果蝇杂交试验 测交bpr b pr b pr 表型观察值独立分配的预期值 子代bpr黑体210 120 亲本型bpr紫眼 野生型240 120 pr 重组型b+ 黑体 14 120 b pr t pr 紫眼 16 120 b pr 总和 480 80
摩 尔 根 的 果 蝇 杂 交 试 验 2 亲本杂交 b pr + + b pr + + 测 交 b pr + + b pr b pr 表 型 观察值 独立分配的预期值 子 代 b pr 黑体 210 120 亲本型 b pr 紫眼 + + 野生型 240 120 b pr 重组型 b + 黑体 14 120 b pr + pr 紫眼 16 120 b pr 总和 480 480
Linkage连锁遗传现象 Linkage: the genes should travel as a unit through meiosis because they are physically attached to the same strucfure 连锁遗传现象:亲本所具有的两个性状 在F2中常常联系在一起而遗传的现象
Linkage: the genes should travel as a unit through meiosis because they are physically attached to the same structure. 连锁遗传现象：亲本所具有的两个性状 在F2中常常联系在一起而遗传的现象。 Linkage连锁遗传现象
Explanation for linkage 连锁遗传现象的解释 Red. lon Red. lon ■ The gene for (Self-fertilized) R different characters Parental Recombinant Recombinant Parental are located on the same chromosome Parenta 两个非等位基因处 在一对同源染色体 R 上 Recombinant G White, long Rt R Parental Red short white, lng vArre short
◼ The gene for different characters are located on the same chromosome. 两个非等位基因处 在一对同源染色体 上 Explanation for linkage 连锁遗传现象的解释
Frequency of recombination as a measure of linkage intensity Calculation of frequency of recombination The most direct way of estimating the frequency of recombination is to use a testcross Linkage phase连锁相 Coupling相引 Repulsion相斥
Frequency of recombination as a measure of linkage intensity ➢ Calculation of frequency of recombination ✓ The most direct way of estimating the frequency of recombination is to use a testcross ➢ Linkage phase 连锁相 ✓ Coupling 相引 ✓ Repulsion 相斥
A test cross for linkage O A heterozygote for two linked genes is testcrossed to a recessive homozygote. R L Coupling and repulsion 包國 Red, long White, short linkage phases in double heterozygotes hEgm在双杂合子中的相引相和 回励 相斥相 Red, long Red, short White, long White, snort 450 42 38 470 Coupling Repulsion heterozygote heterozygote 80 recombinant R L 920 parental Frequency of recombinants 8008 80+920 O The low frequency of recombination indicates that the genes are rather tightly linked
A test cross for linkage Coupling and repulsion linkage phases in double heterozygotes 在双杂合子中的相引相和 相斥相