Abstract：The Bt gene expression cassettes of GM cotton 33B and GK-12 were sequenced and analyzed. Differences were found both in the Bt gene and the junction region of Bt gene/terminators except the junction region of CaMV 35S promoter/Bt gene. In order to detect the two transgenic cotton lines, three specific primers, MG-P1, MG-P2 and MG-P3, were designed and the duplex PCR detection method was established based on the differences. Forty transgenic cotton samples were tested by this duplex PCR method, thirty-two samples were identified to contain 33B Bt gene structure, six samples were identified to have GK-12 Bt gene structure, and two samples were identified to have both 33B and GK-12 Bt gene structures.
