Abstract: Objective To analyze genetic diversity and relationship of two closed colonies of SD rats from Beijing and Shanghai respectively.Methods Seven microsatellite loci were tested by Hardy-Weinberg equilibrium (Hardy-Weinberg equilibrium,HWE),meanwhile,the values of the allele frequency,gene heterozygosity,polymorphic information content (PIC),the genetic distance and some other indexes were counted.Results The average number of observed alleles are 4.857 1 and 5.142 9 in two colonies respectively.The average observed heterozygosity were 0.647 6 and 0.585 7,the average PIC were 0.644 5,0.667 6 respectively.Three and two loci showed evident deviation from that of the HWE (P<0.05) in SD rat colony from Beijing and Shanghai respectively.The unbiased genetic distance of the two colonies was 0.158 2 (Nei 1978).Conclusion The genetic diversity of SD rat colonies from Beijing and Shanghai are relatively rich.There are medium level of genetic differentiation between the two colonies.Microsatellite marker technique is an effective mean for genetic monitoring for closed clolony of SD rats.

Key words: SD rat, Microsatellite DNA, Closed colony, Genetic analysis