Kinship determination using DNA markers

Abstract

Autosomal and Y chromosome short tandem repeats (STRs) and mitochondrial DNA polymorphisms are the most commonly used molecular tools for determination of kinship. To report a revision of 1,120 kinship cases (paternity and others) analyzed in our laboratory. Revision of all kinship cases analyzed between years 2001-2006. Autosomal and Y chromosome STRs and mitochondrial DNA polymorphisms were analyzed in DNA extracted from blood samples. Paternity was excluded in 27.2% of cases. This figure did not change significantly along years. Most paternity exclusions were confirmed by the discordance in 5 genetic markers (30.5%), followed by exclusion of 4 and 6 genetic markers (20.3 and 20% respectively). Two studied cases were paternal and maternal exclusions, corresponding to a change of children between two families. In one case, the paternal line was assessed through Y chromosome markers, studying 16 STRs of this chromosome, positively confirming this paternal relationship. Another case was analyzed for maternal line using mitochondrial DNA analysis. In six cases, a genetic marker with a paternal-sibling mutation, was observed. The criteria for the determination of mutation was the finding of only one discordant marker between at least thirteen markers analyzed in each case. Also, an increase or decrease in one unit repeated in tandem (tetranucleotide) between the alleged father and the son was also required. One subject had a double mutation. In this case, paternity was confirmed analyzing thirteen autosomic STRs and five Y-STRs. The authors have acquired great expertise in kinship analysis and had established criteria to solve complex kinship cases.