Abstract: Objective · To establish a method for identifying the chimeric rates in Down syndrome chimeric mice, and study the chimeric rules in different organs. Methods · The proportion of trisomic cells (Tc1 cells) in different organs was calculateddetecting the relative quantity of human chromosome 21 (Hsa21) and mochromosome 15 (Mmu15) in samples. The relative quantity of Hsa21 and Mmu15 was evaluated with specific primers for genes SIM2 on Hsa21 and Derl1 on Mmu15, respectively,quantitative real time PCR (qPCR) technology. Results · Three mice were chimeras and the chimeric levels of Tc1 cells were different in various tissues. The chimeric rates in hearts of these 3 mice were 8.98%, 21.71% and 57.70%; in cerebellums, the chimeric rates were 5.62%, 20.17% and 40.43%; in brains, the rates were 8.48%, 15.35% and 20.45%; in livers, the rates were 2.66%, 6.50% and 16.84%; and in spleens, the rates were 1.73%, 3.80% and 11.80%. Conclusion · The chimeric rate of trisomic cells in Down syndrome chimeric mice can be detectedqPCR technologyusing primers for genes on specific chromosomes. The chimerism occurs in the hearts, cerebellums, brains, livers and spleens of the chimeric mice and the chimeric rate of Tc1 cells tends to be the highest in the hearts.

Key words: Down syndrome, chimera, momodel, quantitative real time PCR, chimeric rate