Beyond STRs: The Role of Diallelic Markers in Forensic Genetics

Short tandem repeat (STR) polymorphisms have been firmly established as standard DNA marker systems since more than 15 years both in forensic stain typing as well as in paternity and kinship testing. However, when analyzing genetic relationships in deficiency cases, STRs have a couple of disadvantages due to the sometimes poor biostatistical efficiency as well as the possibility to observe one or more genetic inconsistencies that could also be explained by mutational events. In such situations, additional robust markers with negligible mutations rates such as single nucleotide polymorphisms (SNPs) and insertion/deletion markers (indels) can be used as adjuncts to provide decisive genetic information in favor for or against the assumed relationship. Both SNPs and indels can now be typed more easily using multiplexes of up to 50 loci based on fragment length analysis on instruments available in all routine forensic and paternity testing laboratories, thus making it possible to extend the range of markers beyond the currently used STRs.