Y-chromosomal kinship estimation for forensic familial searching: YMrCA to the rescue

The Y-chromosome can be used as an identification method to find paternally related males of the perpetrator. When a close Y-haplotype match is identified, the time to their most recent common ancestor (tMRCA) needs to be estimated to reconstruct their genealogy. To date, two mutation models and three online tMRCA calculators exist. But, they do not include individual mutation rates with multi-step changes, while ignoring hidden multiple, back or parallel modifications. To improve tMRCA estimation, we developed a user-friendly calculator, the 'YMrCA', including all previously mentioned mutation characteristics. Here, a case using genealogical pairs with confirmed biological kinships visualizes the good estimation performance of the YMrCA compared to the state-ofthe-art. Even when genealogical pairs have equal number of mutations, the YMrCA still estimates the correct number of generations due to the inclusion of individual Y-STR mutation rates and the different mutational influencing factors.