Abstract: Objective To analyze the change of genetic structure of KM mice colonies between 1990 and 2010. Methods KM mice colonies (18 mice in 1990 and 50 mice in 2010) were monitored by biochemical markers under instruction of national standard GB/T 14927.1-2008. POPGENE 1.32 software was used to process the data. Results In 1990, average heterozygosity is 0.262 5, polymorphism information content is 0.206 5. In 2010, average heterozygosity is 0.161 5, polymorphism information content is 0.130 7. By compared with the two colonies, population differentiation coefficient is 0.122 4 and the genetic distance is 0.095 1. Conclusion After 20 years outdred, the KM colony has medium change of population differentiation , but still be considered as same strain from the point of population genetics.

Key words: KM mice, Genetic structure, Biochemical markers