A grandparent DNA test calculates the likelihood of relatedness between a child and one or both grandparents.
A child inherits exactly 50% of its genes from its biological mother and 50% from its biological father, that child shares exactly 25% of its genes with each biological grandparent. If both biological parents of the alleged parent are tested and they do not possess the paternal or maternal genes between them, then they are excluded ruled out as the biological grandparents. When both biological parents of the alleged parent possess the paternal or maternal genes between them, they are not excluded as the biological grandparents.
It may not be possible to obtain conclusive results in a grandparent DNA test if both alleged grandparents are not tested. We recommend testing both alleged grandparents as well as one parent if possible to achieve the most accurate results, similarly to the Missing Parent DNA test.
It is also important to understand that, in reporting the results of a DNA grandparent test, the laboratory assumes that the tested alleged grandparents are, in fact, the biological parents of the unavailable, alleged parent. If there is any question regarding the paternity of the unavailable alleged parent, then the alleged biological grandfather should not be tested.
All grandparentage tests utilize stringent, validated testing procedures and include up to 22 STR loci plus the gender identification marker amelogenin in order to achieve 100% accurate results.
