While the so-called classic or conventional serological traits (blood group, serum proteins, enzymes, HLA, etc.) were once drawn on, the IFG relies only on highly informative DNA systems.
DNA (the abbreviation of deoxyribonucleic acid) carries the inherited genetic information of humans. The tests carried out at the IFG are based solely on so-called STR systems (short tandem repeats, also known as microsatellite systems). They are highly individualised non-coding DNA systems, which differ between individuals only in the length of their repeated units. For this reason, such systems are also described as length polymorphisms.
With the help of polymerase chain reactions (PCR) it is possible to specifically determine and replicate one section of the genome (of many thousands). As the alleles have different lengths, they move through a separation medium at different speeds when electric current is applied.
The STRs used in forensic analysis have between four and five nucleotides per repeated unit and generally more than eight different lengths of chromosome section (alleles) in the general population. These alleles occur at different frequencies in the population, meaning that a sufficient number of STR systems are required for a valid assessment (guidelines call for a minimum of 15 STR-Systems).
The STR systems used have been validated by a number of intensive studies, including those carried out in our laboratories. International recommendations and guidelines were and are observed in these studies. Among other things, the validation studies include comprehensive studies of the genetics of the relevant populations as well as regular participation in quality control testing (including the biannual Deutsche Gesellschaft für Abstammungsbegutachtung (federal association of parentage appraisers) and GEDNAP (German DNA Profiling Group) inter-laboratory tests).