Population genetic data, comparison of the repeat structure and mutation events of two short STRs

The short tandem repeat (STR) systems D3S1545 and D7S1517, both small size STRs (fragment lengths <160 bp), were investigated in a population sample of German Caucasoids. New primer sequences more closely flanking the repetitive region were designed for D3S1545. For D3S1545, 7 alleles could be found (heterozygosity 0.68) while 11 alleles could be typed for D7S1517 (heterozygosity 0.83). Additionally, sequencing of selected alleles was carried out to establish the allele nomenclature and to clarify the structure of the tandem repeat arrays. D3S1545 showed a uniform GATA repeat structure but, in contrast, the repeat stretch of D7S1517 showed a compound structure characterised by different numbers of GAAA and CAAA repeats. Two isolated cases of a new mutation could be confirmed for D7S1517. The alleles of these two family constellations were characterised by sequencing and the probable mutational events were demonstrated.