Abstract：Droplet digital PCR(ddPCR) is a new absolutely quantitative method based on Poisson distribution, which shows huge potential applicability in accurate quantification of nucleic acid. Herein, we developed the ddPCR method to evaluate the exogenous gene copy number in genetically modified organisms (GMOs) as the example from genetically modified rice(Oryza sativa) T1c-19 and transgenic human lactoferrin gene goat(Capra hircus) 134 examples, and the results was also compared with those from quantitative Real-time PCR (qRT-PCR) and Southern blot. The results from qRT-PCR and ddPCR for cry1C* in T1c-19 were comparatively unanimous (~2 copies), while 1 copy was reported in literatures by Southern blot. The copy number from ddPCR was higher than that of qRT-PCR for bar gene in T1c-19, 2.09 and 1.51 copies respectively. Same result (~1 copy) was obtained from qRT-PCR and ddPCR for HLF gene in goat 134. Therefore, the ddPCR was well developed as one novel method for estimating transgene copy number with high accuracy, and which may be widely used in the exogenous genes copy number analysis in GMOs.
