Background: Highly polymorphic autosomal short-tandem-repeat (STR) analysis can be useful in most kinship testing. Y-chromosome-specific STRs, in contrast, have been increasingly applied for the verification of equivocal paternal genetic transmissions.
Study design and methods: A total of 338 unrelated males were first typed for the 9-loci Y-STR European minimal haplotype (minHt). Samples with haplotypes that were found at least two times were subject to further study by a commercially available 17-Y-STR multiplex set (AmpFlSTR Yfiler). A separate clinical study for 113 various kinship identifications of male genetic transmission were then conducted by a panel consisting of 18 autosomal STRs and complemented by both Y-STR multiplex sets and their respective results compared.
Results: For the 338 individuals, a total of 270 haplotypes were identified after the minHt study, of which 234 were unique. Among the rest of the 104 samples, AmpFlSTR Yfiler identified 82 other unique haplotypes. Altogether, 324 different haplotypes were observed; 316 (97.5%) were unique whereas 8 were shared by two to seven times. The haplotype diversities for the minHt and the AmpFlSTR Yfiler were 99.75 and 99.96 percent, respectively, whereas the powers of discrimination (PDs) were 79.88 and 95.86 percent, respectively. Despite a lower PD for minHt, there was no discrepancy on the clinical setting for personal identification between the two Y-STR sets in an allegedly true male lineage transmission involving 66 cases with 24 father-son, 19 siblings, 9 uncle-nephew, 8 grandfather-grandson, 3 cousins, and 3 half-siblings. For 47 other cases with a false allegation of paternity, exclusion was made for all without ambiguity by either Y-STR panel.
Conclusion: The 9-loci minHt Y-STR set is adequate to complement conventional autosomal STRs for kinship studies where Y-lineage transmission is concerned.