Validation of the X chromosomal STR DXS7424 which is closely linked to DXS101

Abstract

In some special cases of post-mortem identification and deficiency paternity testing, the investigation of X-chromosome (ChrX) markers may be more informative than the investigation of autosomal polymorphisms. We analysed the trinucleotide repeat polymorphism DXS7424 (GDB-G00-577-633), cytogenetically mapped at Xq22. PCR fragment length measurements, sequencing and linkage studies were carried out. In a sample of 474 unrelated Germans, we found 12 alleles with the regular repeat structure (TAA) [9–20]. The population sample was characterised by the following features: polymorphism information content (PIC)=0.776; heterozygosity (Het)=0.836; mean exclusion chance (MEC)=0.762. Kinship tests revealed a typical X-linked inheritance without any mutation. Significant deviations from the Hardy–Weinberg equilibrium (HWE) were not established. Linkage studies confirmed close linkage to DXS101. It was not possible to exclude linkage disequilibrium between DXS101 and DXS7424 through haplotyping of 390 male individuals.