Document Type

Brief Communication


The allele frequency distributions in a series of Croats were analyzed for six unlinked polymorphic DNA loci: THOl, FESFPS, VWA01, APOB, D1S80, and D17S5. The allele frequencies were determined for 100 unrelated genomic DNA samples. The observed heterozygote frequencies of the loci ranged from 0.63 to 0.76; however, the expected heterozygosity ranged from 0.68 to 0.82, with only D17S5 having a significant excess of homozygous phenotypes (p < 0.001). The excess homozygosity seen in the D17S5 system may be due to allelic drop-out and warrants further technical analysis of that system, given the uniform lack of significant deviation in the other five systems. The forensic usefulness of these systems can be measured using two different statistics: the power of discrimination and the likelihood of a coincidental match. The power of discrimination ranged from 0.85 to 0.94 for the 6 systems with the combined likelihood of a coincidental match based on these 6 systems of 1 in 3.6 million, or slightly less than the population of Croatia. A second, more conservative estimator of the likelihood of a match is based on the most common phenotype for each system. If someone had the most common phenotype for each of the 6 systems, the chance of a coincidental match would be approximately 1 in 64,000. For paternity testing the usefulness of a system is measured by the average power of exclusion or (1 — power of exclusion), the random man not excluded. The average power of exclusion, based on observed heterozygosity, ranged from 0.33 to 0.53, and the average power of exclusion based on the expected heterozygosity ranged from 0.39 to 0.64. The combined average power of exclusion was 99.2% for these 6 systems, using the expected heterozygosity. Based on the results of testing these six systems, there is no significant substructuring within the southern Croatian populations, and these systems provide a useful tool for forensic, paternity, and anthropological applications.