Abstract: Objective To develop a PCR-based X-STR kit for typing of 16 X-STR loci and investigate the polymorphisms of the X-STR markers. Methods Sixteen STR loci （GATA165B12, DXS101, GATA172D05, HPRTB, DXS981, DXS8378, DXS6795, GATA31E08, DXS6809, DXS6803, DXS9902, DXS6807, DXS7423, DXS7133, DXS6810 and DXS7132） located on X chromosome were selected. The primers for multiplex PCR were designed by Primer Premier 5.0 software and labeled by four fluorescences（FAM, HEX, TAMRA and ROX）. The developed multiplex PCR system was used for investigating the polymorphisms of the X-STR markers in Han populations. Results The 16-plex amplification system named IDtyper X-16 was successfully developed and validated. Among the 16 X-STR loci, DXS7133 and DXS7423 were found to be moderately polymorphic and the other 14 X-STR markers were highly polymorphic（PIC>0.5, H>0.5）. The cumulative discrimination power in females and in males were 0.999 999 999 999 97 and 0.999 999 993 respectively in Han population. The combined power of exclusion in trios and in duos were 0.999 999 93 and 0.999 990, respectively. Conclusion The IDtyper X-16 kit is highly valuable in forensic science and is suitable for paternity testing in disputed cases.

Key words: forensic genetics, X chromosome, polymorphism, genetic, STR