Giulia Filippini

Development and forensic validation of a new multiplex PCR assay with 12 X-Chromosomal short tandem repeats

One multiplex system for the co-amplification of 12 X-chromosomal short tandem repeats (STRs) DXS7132, DXS8378, DXS6809, DXS7133, DXS6789, DXS7424, GATA172D05, HPRTB, DXS7423, GATA31E08, DXS101, DXS6807 and amelogenin was analysed in a sample of 200 (100 males and 100 females) unrelated healthy individuals living in Northern Italy. The chi2-test for genotype distribution of the X-chromosomal STRs showed no significant deviation from the Hardy-Weinberg equilibrium (HWE). Allele frequencies between female and male samples were not significantly different in all examined markers. In the kinship cases involving 40 family trios with daughter and 10 father/daughter duos, no mutation was detected. The combined power of discrimination (PDc) of the 12 X-STRs for both females and males was PDc > 0.999999.

Two additional reports of deletion on the short arm of the Y chromosome

Deletions on the short arm of the Y chromosome involving the amelogenin Y gene (AMELY), located on Yp11.2, can be misleading for sex typing with serious consequences in forensic applications and prenatal diagnosis. In this study, we describe two AMELY null cases concerning two unrelated Italian males from Northeast Italy. PCR amplification of short tandem repeats on the Y chromosome (Y-STRs) showed a lack of AMELY and DYS458 markers. The presence of all the other markers located on the Y chromosome and of the SRY gene in both samples led us to conclude that a deletion had occurred in a portion of the short arm of the Y chromosome. Twenty-three Y-specific sequence tagged sites (STSs) were chosen to delineate the deletions length, which was estimated to be in the range of 3.35-3.87Mb for one sample and 1.51-2.58Mb for the other. These and previous findings suggest that in all cases where potential AMELY drop out has occurred, it should be used additional specific Y chromosome markers or human DNA quantification methods that specifically quantify male DNA using target male genomic markers, which not being located within the deletion regions, allow an accurate sex identification.