Abstract:
Short tandem repeat (STR) typing has become
the standard technique in forensic methodology for the
identification of unknown samples. National DNA databases
have been established that contain STR genotypes for
intelligence purposes. Due to their success, national DNA
databases have been growing so fast that the number of
advantageous matches may become a logistic problem for
the analysts. This is especially true for partial STR profiles
as they display reduced discrimination power. To overcome
this drawback, modified versions (so-called mini-STRs) of
existing loci were introduced as well as new loci to improve
the information content of (partial) STR profiles. We pursue
an alternative approach that makes use of nucleotide
variation within the amplified STR fragments, which can
be discerned by mass spectrometry. We have developed an
assay that determines molecular masses from crude STR
amplicons which were purified and separated by a liquid
chromatographic system directly hyphenated to an electrospray
ionization mass spectrometer. We present here new
population data of forensically relevant STRs in Khoisan
and Yakut populations. These autochthonous groups were
selected as they may harbor additional STR alleles that are
rare or unobserved in modern humans from cosmopolitan
areas, especially for the Khoisan, which are known to
represent a very ancient human population. The analysis of
the molecular mass of STRs offered a widened spectrum of
allele variability escorted by enhanced forensic use. Thus,
established STR data derived from fragment size analysis
can still be used in casework or in the context of
intelligence databasing.
