Utility of X-chromosome SNPs in relationship testing

X-chromosome markers may complement the results obtained from other genetic markers in complex relationship cases. Until now, reports on relationship testing using X-chromosome markers have mainly included data of short tandem repeats (STRs) while little data on single nucleotide polymorphisms (SNPs) in relationship testing have been published. We selected 25 highly polymorphic biallelic SNPs distributed through the human X-chromosome. One 25-plex PCR reaction and one 25-plex single base extension (SNaPshot) reaction were developed. The maximum size of the PCR products was 120 bp and the size of the SBE primers varied between 18 and 85 nucleotides. We analyzed the allele and haplotype frequencies in 1078 unrelated males. All the SNPs were polymorphic and the lowest minor allele frequency was 0.103. All the haplotypes were unique. The forensic parameters were calculated in the Danish and Somali populations. In the Danish population (N = 93), the power of discrimination (PD) in females was one in 4.4 X 10(9) individuals and the PD in males was one in 2.6 X 10 6. The PD in Somalis (N = 91) was one in 2.7 X 10(9) in females and one in 1.7 X 10(6) in males. Finally, we present an example of how the 25 X-chromosome SNP-multiplex may help to solve a complex immigration case. (C) 2008 Elsevier Ireland Ltd. All rights reserved.