Grandparent DNA results typically involve genetic analysis with a set of grandparents and a target child. Usually, the test is used to establish the paternity of the child. However, sometimes a grandfather may use the grandchild to determine if he is the biological father to his own children.

Understanding DNA results can be confusing if you’re not familiar with them. While people may grasp the conclusion at the bottom of the report, the DNA profiles at the top can be unfamiliar.

We frequently receive requests from our clients to further explain the DNA analysis shown at the top of the results.

Read about our dna test for grandparents

DNA Testing Basics

  1. DNA Matching: Children have a genetic match with each set of grandparents on every genetic locus. This entails that one allele matches with a paternal grandparent, while the other allele matches with a maternal grandparent.
  2. Probability of Relationship: Results are given as a percentage and probability. This indicates the likelihood that the alleged grandparents are the biological grandparents to the child. A probability of 0%-8% indicates it is very unlikely for the biological relationship. While a probability of 92% and higher is considered a positive match.
  3. Inclusion vs Exclusion: Exclusion implies inconsistencies between the child and the grandparents, indicating an unsupported relationship. Conversely, inclusion suggests that the grandparents cannot be excluded because the genetic markers sufficiently match.
  4. Legal vs Non-Legals Tests: Relationship tests can be conducted for court admissible purposes or simply for personal knowledge. Legal tests follow specific protocol and strict chain of custody, to be admissible for court and other legal proceedings. Non-legal tests offer the same accuracy but lack notarization for use in legal settings.
  5. Chain of Custody: Chain of custody is required for legal tests. Samples must be collected and handled in a way that ensures they are not tampered with.
  6. Accuracy: When the father is unavailable, a grandparent test provides the next best accuracy. Grandparents replicate the full DNA profile of the father, offering the same level of accuracy as a standard paternity test when both grandparents are used. Choosing a reputable testing laboratory is crucial for achieving the highest accuracy.

Let’s look at a couple sample reports for a better understanding on how to read the results. The first sample shows a non-legal test with a positive result. The first sample illustrates a non-legal test with a positive result, while the second represents a legal test with a negative result.

Positive Grandparent DNA Result

In the illustration below, we have a genetic analysis that includes Mary Doe as the child, Denise Doe as the alleged paternal grandmother and Jerry Doe as the alleged paternal grandfather. There are 5 lines presenting the genetic analysis. The first line lists the name of the specific loci being examined. The next 3 lines represent the individuals testing. The “C” is the child’s DNA, PGM is the paternal grandmother’s, and PGF is the paternal grandfather’s. The final line is the PI. The PI is the probability index.sample report for positive grandparent dna test result

Genetic markers in individuals are reflected as alleles, depicted as numerical values within the report. Every individual has one or two alleles in each marker. If they have 2 alleles, one of the alleles comes from their father and the other from their mother. If an individual only has one allele, this indicates they received it from both their mother and their father.

Since the father receives one allele from his father and one allele from his mother, the child will match with one or the other paternal grandparent in each marker.

Looking at the first marker of the report, we are able to see the child matches with the grandmother. In the following marker, the child coincidentally matches the same allele with both grandparents. Some alleles are very common in certain markers. So, this is not out of the ordinary.

Lastly, we can take a look at the PI. The PI is the probability index for that specific marker or pair of markers. The PI is based off how often a specific allele size is seen in the specific marker. If the allele is not seen commonly, then the PI will be larger. However, if the allele size is more common in a certain marker, then the PI will be much smaller.Probability index for positive grandparent dna result

Now that you understand how the DNA matches work, let’s look at the full report. It is clear that the child matches with at least one grandparent on each genetic marker. So, we can skip down to the conlusion. In the conclusion, it reads that Jessica and John cannot be excluded as the biological grandparents. This means that they are included and that their son is the biological father.

It is important to notice the disclaimer on this report stating that the laboratory cannot identify the individuals testing. The reason for the disclaimer is because this report would be from a home testing kit. Since, our staff and collectors were not present for the collection, we have no proof who was collected. Our clients could collect samples from anyone. This is why home testing kits do not hold up for legal matters.

In our next sample report, we will show a report that holds up for legal purposes. Legal tests require notarized results along with a fully executed chain of custody. It must be collected by a non bias collector.

Negative Grandparent DNA Result

In the following example, we have included a negative report meaning that that grandparents are not the biological grandparents to the child.

Below is another illustration depicting a genetic analysis, featuring Mary Doe as the child, Denise Doe as the alleged paternal grandmother, and Jerry Doe as the alleged paternal grandfather. The analysis comprises four lines. The first line identifies the specific loci under examination, while the subsequent three lines represent the DNA samples of the individuals tested. The abbreviations denote the child’s DNA as “C,” the paternal grandmother’s as “PGM,” and the paternal grandfather’s as “PGF.” Notably, there is no Paternity Index (PI) in this instance due to exclusions.sample report for negative grandparent dna test result

As highlighted in the previous example, for a positive result, a child must match at least one allele with either grandparent. Let’s examine a couple of markers randomly selected from the report: FGA and D8S1179. In both markers, it’s evident that the child’s alleles do not match those of either grandparent, constituting inconsistencies.FGA marker negative grandparent test result

The report concludes that there were inconsistencies across multiple markers, which do not support a positive result. Therefore, the conclusion states that Denise and Jerry’s son is not the biological father of the child.

Wrapping Up: Understanding Grandparent DNA Results for Clarity and Resolution

Understanding grandparent DNA results is crucial for accurately determining biological relationships. By interpreting genetic markers and probabilities, one can navigate through the complexities of DNA testing with clarity. Whether for personal knowledge or legal purposes, discerning the implications of DNA results ensures informed decisions.

In examining both positive and negative reports, we’ve illustrated the importance of thorough analysis and the role of legal standards in establishing biological relationships. While non-legal tests offer insights, legal tests provide the necessary rigor and reliability for formal proceedings.

Ultimately, each report tells a story, unraveling the mysteries of ancestry and paternity. Through careful interpretation and adherence to established protocols, the truth can be unveiled, bringing clarity and resolution to complex familial questions.