Grandparent DNA testing is often used to determine the paternity of a child when the father is not available for testing. This is often the case when the father is deceased and the mother is trying to obtain Social Security benefits or a will is being disputed. By testing the grandparents, we are able to determine the genetic profiles of any of their biological offspring such as that of the alleged father. A sample is obtained from the mother, the child and typically both of the alleged father's parents. By comparing the DNA variations of the mother and child, it is possible to identify the variations that the child inherited from his or her biological mother. The remaining DNA variations (paternal variations) must have come from the biological father. By determining the genetic profile of the grandparents, you are able to determine the genetic profiles of any of their biological offspring and then use this information to include or exclude them, as the biological grandparents of a tested child.
If the DNA profiles from the grandparents do not contain the paternal variations observed in the child, they are excluded as the biological grandparents and therefore, the alleged father is excluded as the biological father. In cases where the grandparents in combination contain all of the required paternal variations, a statistical analysis is performed to calculate the probability of grand parentage is determined. This is then used to calculate the probability that the untested alleged father man is the true biological father of the child. For a grandparentage testing (mother, child, and both parents of the alleged father) UNTHSC guarantees a minimum probability of 99.9% of paternity for inclusions. It should be noted that in grandparentage testing, an assumption is being made that the grandfather is indeed the biological father of his deceased son. It is also assumed that the deceased alleged father did not have another male relative, such as a brother, who could have fathered the child. The staff at UNTHSC will ensure that all relevant questions are asked and clarified prior to testing, to ensure the most accurate result is achieved. Testing between a grandfather and grandson can also be performed using our Y-chromosome STR loci to determine whether a common paternal lineage exists between the two.