Abstract: Objective To construct STR slippage model and study factors involved in this procedure. Methods DNA samples were amplified with the technology of Degenerate oligonucleotide- primed PCR ,then their products were taken as later DNA template and their STR genotype were analyzed by optimizing several factors. Results STR slippage model was constructed. Conclusion Several factors were involved in the produce of STR slippage, such as amount of modulate DNA, concentration of MgCl2, property of DNA polymerase, motif sequence of STR loci, sample, etc.

Key words: short tandem repeat(STR), slippage, model, degenerate oligonucleotide- primed PCR