Grand Parents

A grandmother and child are compared to determine if her son could be the father. After testing 16 markers it is found that there was only a 30.80% probability of relationship (69.20% unrelated). We report any probability less than 80% as inconclusive. In other words, you cannot draw a conclusion from the information when it is below 80%. Ideally, we’d like to have the probability as close to 100% as possible in either direction (related or unrelated). We asked for the mother’s sample and tested with the 16 marker test. The results were also inconclusive with a probability of relationship at 43.88% (56.12% unrelated). After testing 41 markers, the probability of the grandmother being related dropped to 0.01%, meaning that she was 99.99% probable to be unrelated to the child.

99.99%

In another grandmother and child comparison with 16 markers, the results were found to be a probability of relationship of 27.09% (72.90% probable to be unrelated). The mother was unavailable for testing and we proceeded with the 41 marker test. We found the probability to be 99.70% in favor of a relationship with the child. This illustrates the power of additional markers and why our inconclusive level is set at 80%. The 16 marker test was simply not strong enough and, at times, produce misleading results.

This grandmother and child DNA comparison with 16 markers produced a nearly equal probability of being related or unrelated at 48.85%. After testing 41 markers, the probability increased to 87.26% probability of relationship. Of course, we would like the percentage to be higher and asked for the mother’s sample to strengthen the case.

In this case, the alleged grandfather, child and mother were tested. The probability of relationship at 16 markers was 57.56%, which is inconclusive. The probability increased to 99.99% after testing the three participants with the 41 marker test.