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 linkedA 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