Considerations from the European DNA profiling group (EDNAP) concerning STR nomenclature

(1) The nomenclature of any STR follows from comparison with a control allelic ladder; availability of reference allelic ladders is central to any scheme. The components of an allelic ladder should be sequenced. (2) The DNA commission recommended a nomenclature based upon the number of repeat sequences present in an allele. Whereas this method is suitable for typing simple STRs, complex hypervariable repeats such as ACTBP2 do not conform to a simple repeating structure. We propose that designation of complex STR repeats such as ACTBP2, D11S554 and APOAI1 follows from the size of specific alleles. Because the size is dependant upon the primers utilised, the size is not definitive (it may also be dependent upon the internal structure of the allele), hence designations are prefixed with the term 'type-'. (3) Allelic ladders should span the entire known range of the common alleles of a locus. (4) It is not necessary for every known allele to be represented in the allelic ladder. The common types should be present; alleles intermediate to two common types can be designated by simple extrapolation. If possible, there should be a maximum 4bp gap between allelic ladder markers for tetrameric and dimeric STRs (if the STR repeat is greater than 4bp, then the maximum gap defaults to the size of the repeat). (5) The designation scheme to be used for a given locus is dependent upon the characteristics of the locus itself. If possible the designation should follow the recommendations of the DNA commission unless its allelic structure precludes that option.