Genetic variation and sequence studies of a highly variable short tandem repeat at the D17S976 locus

The STR locus D17S976 was investigated by PCR amplification and native polyacrylamide gel electrophoresis in 158 unrelated Austrian Caucasians. No deviations from Hardy-Weinberg expectations were observed. The mean exclusion chance was 0.792, the discriminating power was 0.980 and the observed heterozygosity rate was 0.873. Moreover two alternative denaturing electrophoretic protocols are proposed. An allelic ladder consisting of 14 sequenced alleles (236-288 bp) was constructed. Sequence analysis revealed that the locus contained three different repeat motifs: ATCA, ATCT and ACCT, all of which vary in number between alleles. The aggregate number of the three tetrameric repeat types was used for allele designation. As a repeat with a single base deletion (ATC) was found in both the smallest and the largest alleles, a ".3" was added to the allele designation in those cases. Therefore the smallest allele is designated 19.3, and the largest allele is designated 32.3. To evaluate the exact extent of sequence variation more extensive sequence studies are necessary.