The Grandparent test

12 Aug 2017

The Grandparent test is one of the various relationship tests available other than the paternity test itself.  In most cases these types of tests are carried out in order to confirm paternity if the father is not available or has passed away.  A less direct link exists in between a grandchild and his grandparents as normally this child would carry genetic markers inherited from the father that have originally originated from the grandparents themselves. 

By comparing their DNA markers we are able to determine if a relationship exists and whether this child in question was actually issued by the alleged father in question.   This can help determine paternity when the father is not available or has passed away.

Is it better to submit one Grandparent or both for testing?

If we had to run only one grandparent against the grandchild being tested, then the laboratory would run a regular relationship test.  With this type of test we are only looking at how similar the DNA fingerprints are.  A percentage probability marking the grade of relationship is then drawn.  This test could yield a correct result, but most DNA testing companies would always suggest that you test both grandparents.   The reason for this is that the child might have inherited certain DNA markers of the father that originated more from the one Grandparent rather than the other.  If the Grandparent tested happens to the Grandparent of whom the genetic markers were not inherited, then the result would yield a false negative. In other words the result would state that no biological relationship exists whilst one could still possible exist.   If one Grandparent is the only option then it would be highly suggested to also include the mother’s sample to improve the precision of the test keeping in mind also of the possibility of obtaining a false negative. Testing both Grandparents would enable to laboratory to issue a Missing Persons Report that will give you a more conclusive answer.

What is a Missing Persons Report (Result with two Grandparents)

When two Grandparents are tested a Missing Persons Report is drawn.  In this report a conclusion is determined if the Grandchild is related to the two Grandparents tested.  In each genetic marker of the Child’s DNA profile, one value is inherited from the father and the other from the mother.  Each genetic marker inherited from the father must have also originated from the Grandparents.  Either one or the other.  The paternity is calculated by matching the child’s DNA profile with all the possible combinations of alleged fathers the Grandparents could have issued.  When a perfect match is found, then this indicates that a link exists.

The Grandfather and the male grandchild (Y Chromosome testing)

All male human beings have a Y Chromosome.   This Y Chromosome caries certain genes that pertain to the male species and therefor is very useful when a direct male link exists.  In the case were a male Grandchild is in question and only the paternal Grandfather is available for testing, a link can be established between by carrying out the Y Chromosome test.  All males inherit the same exact Y Chromosome from their fathers.  If the alleged father, who is not available of has passed away, passed on the Grandfather’s Y Chromosome to his child, then their Y Chromosome should be identical.  The test is carries out by actually comparing the profiles themselves to check whether they are equal or not.  This test however can only be considered valid if no other male relative, who might also have the same Y Chromosome, fathered the child in question.  In this case their Y Chromosome would match in any way.

For any of the above tests it is always recommended to seek professional consultation by contacting a reputable DNA testing company directly.  Genetic consultants know best how to look into your particular case and offer you the best option possible to solve your questions.