[Objective] To learn about the genetic diversity,we studied the five X-chromosomal STR (X-STR) loci in Guangdong Han Nationality Groups.[Methods] The five Loci (DXS6803,DXS981,DXS6809,DXS6789,and DXS7132) were amplified in a pentaplex PCR reaction.PCR products were analyzed using capillary electrophoresis and ABI prism 3100 Genetic Analyzer,with GeneMapper ID 3.1 Analysis Software.[Results] A total of 363 individuals (181 unrelated male and 182 unrelated female) from Guangdong Han population were tested,54 alleles were observed for these loci.Polymorphism information content is 0.6935 ～ 0.8177.Power of discrimination in females was 0.8976 ～ 0.9562.Mean exclusion chance for X-STR in standard trios with daughters was 0.7805 ～ 0.8467.[Conclusion] The five loci in the multiplex system provide high polymorphism information for forensic identification and paternity testing,particularly for difficult paternity deficiency cases.

Objective The aim of this study was to investigate mutations of 41 STR loci. Methods 4546 bloodstain samples were typed from 1932 father–mother–child trios by using AGCU_21+1, AGCU_EX22 and GlobalFiler_ExpressTM amplification Kit. Calculate the mutation rates of STR loci. Results 154 mutations were identified at 32 of the 41 loci. The average mutation rate was 1.0×10-3per locus(95%CI: 0.8~1.1×10-3), and the mutations of SE33 was highest. 152(98.7%) mutation events were one-step mutation, 2(1.3%) events were two-steps. The mutation events occurred in 150 father–mother–child triplets. The mutations in 146(97.3%) triplets occurred at single locus, 8 mutations were observed at two loci in 4(2.7%) triplets simultaneously. 104 paternal and 22 maternal mutations could be determined under 79212 paternal and maternal allelictransfers. The ratio of paternal versus maternal mutations was 4.7:1, and 28 unassigned mutations were observed. Conclusion STR mutation are common in paternity testing, and we should pay more attention to it.

Objective To provide the basic data for forensic application by analyzing the genotypes absence at DYS448 locus. Method 5487 bloodstain samples from unrelated male individuals of Chinese Han population were obtained. 4479 samples was co-amplified using Y-filerTM and AGCU Y-24 kits. 1008 samples was co-amplified using Yfiler PlusTM and AGCU Y-24 kits .Probability of genotype absence was calculated. Results 35 samples of 35 haplotypes among 5487 non-related individuals were found to have DYS448 genotypes absence ,while 2 individuals displayed additional alleles at else locus. Conclusion The probability of DYS448 genotype absence was 0.637%, forensic scientists should pay more attention in practical cases and YSTR database.

Objective To deveplope construct and validate a novel multiplex PCR system comprised of 30 Y-STR markers only with low and moderate mutation rates. Methods 30 Y-STRs characterized by low/moderate mutation rate and middle/high polymorphic was amplified simultaneously in a multiplex PCR system using the six color labeling fluorescence. PCR product was analyzed in a ABI 3500XL Genetic Analyzer. The accuracy, specifity, sensitivity and stability of the system and its validation on the mixtures were evaluated. Results The validation studies demonstrated that the system is a stable, accurate, and sensitive multiplex PCR system. The sensitivity was 0.0625ng DNA. Y-STR could be detection in a male/female DNA mixture ratio of 1:4. Conclusion The primary study demonstrates that this multiplex PCR system is effective and reliable for forensic routine DNA analysis. It will be very helpful for constructing Chinese forensic Y-STR database and population genetic research.