implemented into the PCR reactions after they were washed with sterile water and 90% ethanol. Blood and tissues were obtained in agreement with protocols reviewed and approved by the Institutional Animal Care and Use Committee. Cross-species PCR To easily identify the breakpoint in various gibbon taxa, a PCR system with two different PCR reactions were established. To verify the breakpoint, primers 263C9_BP_L (59-ATTCGTAAGGCAGT- GAGATG-39) and 263C9_BP_R (59-GGTTTGTCCTCACTG- GAATA-39) were used, whereas to confirm its absence, primer 263C9_BP_L was combined with primer 263C9_HSA22_R (59- CTGAGAACTGTATGGAAGACTG-39) (Figure 1B). For both reactions, identical PCR conditions including a pre-denaturation step at 94uC for 2 min., 30 cycles each with 94uC for 30 sec., 55uC for 30 sec. and 72uC for 1 min., and a final extension step at 72uC for 10 min. were applied. Results of PCR amplifications were checked on 1% agarose gels. 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