A relationship test like the grandparent test can be of great assistance  in answering the question of paternity when the father is not available or is deceased.   All genetic markers of the father have originally been inherited from the grandparents themselves so the same genetic information should also be contained in the DNA profiles of the grandparents. 

By looking at their DNA we are able to confirm if the grandchild is indeed a relative of the Grandparents and in turn also determine if the alleged father is the father of the child in question.

Can the test be carried out with only one Grandparent?

The main difficulty with this test lies in whether only one Grandparent is available for this test or both.  When a child inherits genetic markers from the father, we must consider that these markers are generally at random.  It is not possible to know whether the child has inherited genetic markers that originated from the Grandmother, Grandfather or in equal parts.  With only one Grandparent we have half the picture and even though we could possibly obtain a correct answer the main concern is that a negative result could be a false.  If one Grandparent is the only possibility then the test can be carried out, preferably including the mother’s sample to maximize precision, and keeping in mind the risk.  A relationship test is carried out in between the participants to grade the level of similarity in the DNA profiles.  If a positive result is produced the, it is a definite result.  The question remains with a negative result as a lack of similarity could be indicating the Grandchild inherited more of the other Grandparent that is not available rather.  If both Grandparents are available then a Missing Persons Report is issued.  This gives a conclusive answer of whether the Grandchild is really related or not.

Testing with both Grandparents The Missing Persons Report

Together both Grandparents hold the same DNA information that the alleged father holds.   When both grandparents are available for testing in a grandmother and grandfather DNA test, a Missing Persons Report is normally drawn and in this way it is possible to reach a conclusion of the grandchild is biologically linked to them.  By looking at all possible “Alleged Father” combinations (All combinations of all possible offspring issued from the grandparents), it is possible to detect if one of these combinations matched with the grandchild in question.   The alleged father’s DNA profile is composed of values that have been inherited from his parents (The Grandparents).  The grandchild, to be related, need to have a value in each of his markers that matches with the grandparents.  To further more improve the accuracy of the test result,  it is always recommended to also include the sample of the mother.

The male lineage test Grandfather and Grandchild

The male lineage can be determined in between two male persons by the use of a Y Chromosome test.  All male human beings have a Y Chromosome that they inherit from the father.  In the case were a Grandfather wants to determine if hi Grandson if the child of his son then he can carry out a Y chromosome test This will detect if the Y Chromosome profiles are actually identical or not.  You will obtain a confirmation of whether the Grandson comes from the same male lineage or not.  It is important that no other male relative could have fathered the child as this will also give a positive result as the Grandchild would still be related, but not necessarily through the father in question.  This test is extremely useful is the alleged father is not available or has passed away.

Professional advise from a genetic consultant is always highly suggested in order to obtain the most accurate suggestions possible.