Abstract: Objective In order to increase significantly the discriminatory potential of Y-STR systems available to the forensic community, we have developed a system capable of simultaneously amplifying 9 Y-STR loci by fluorescence-labeled multiplex PCR technique. Methods Primers of STR loci DYS434, GATA-A10, DYS438 and DYS439 were labeled with 6-FAM, primers of STR loci DYS531, DYS557, DYS448 were labeled with HEX, and primers of STR loci DYS456, DYS444 were labeled with TAMRA, respectively. PCR products were analyzed using capillary electrophoresis and GeneScan Software on the ABI Prism310 DNA Analyzer. Series experiments were carried out to evaluate the useful value in forensic application such as the sensitivity, male specificity and genotyping DNA different tissues of the same individual. Results 9 Y-STR loci were exactly determined following optimization of the polymerase chain reaction. In a sample of 120 males, a total of 105 different haplotypes was identified, 97 of them being unique. Overall, haplotype diversity was 0.996 8. It was proved that genotyping of these 9 Y-STR loci in some sexual crime should be prior to that of automosomal STR. Conclusion The results suggest that the newly constructed 9-plex will be very powerful for establishing Y-STR database, population genetic studies and mixture stains identification.

Key words: Y chromosome, STRs, multiplex PCR, haplotype