A child inherits exactly 50% of his genes from his biological mother and 50% from his biological father, therefore this child shares exactly 25% of his genes with each biological grandparent.
Based on the number of genetic matches, the lab calculates the statistical probability that the presumed grandparents are biologically related to the child. To perform this test, the grandfather and grandmother must be the biological parents of the presumed father or mother .
Since the child has only 25% of genes in common with his grandfather and 25% with his grandmother , it is mandatory that both biological grandparents participate in the test with the child .
On average, the test of parentage grandparents allows the laboratory to determine only half of the genes of the alleged parent.
It is always recommended to test one or both of the known parents to get the most accurate results possible . Since the genetic heritage of children is only half of that of the parents.
The parents' participation in the grandparents' relationship test makes it possible to exclude half of the child's DNA, leaving the other half for comparison with the DNA of the person sought. This improves the reliability of the results.
In this sense, it is very important to do this test with the biological parents (grandparents) of the presumed parent (of the father or mother sought) . Otherwise, the test will not be conclusive.
If in your research of kinship, the doubt relates to presumed parents coming from the same family, then all the known relatives must take part in the test with the children . Otherwise, the results may lose precision. As a general rule, the more genetic information available, the better the chances of a successful test.
Frequently Asked Questions
How accurate is a grandparent DNA test compared to a paternity test?
A grandparent parentage DNA test is less accurate than a paternity test because the conclusiveness of the results can vary. Thus the probability of a relationship will depend on the number of participants and the initial family situation. To reinforce the conclusiveness of the test results, we recommend that both biological grandparents participate in the test and if possible that the mother (or father depending on the situation) of the child also participates. When the grandparents and the mother participate in the tests, the probability of paternity is almost always lower than a paternity test.
Can we do the grandparent parentage test using only one grandparent?
In fact, it is possible. You can do this DNA test using samples from just one grandparent and the child; however, the chances of obtaining conclusive results are drastically reduced. If possible, we always recommend including DNA from the mother (or father depending on the situation) in grandparent DNA testing. Be careful, some laboratories refuse the test with only one grandparent, judging the results not reliable enough for customers.
Can the DNA test be done without the known parent (mother or father according to situation )?
Yes, a grandparents test can be done without the mother, although it is strongly recommended that she is included as well. His participation helps analysts determine more clearly which of the child's DNA comes from the father's side and from the mother's side and can also help strengthen the probability of a relationship percentage. Same principle in the search for maternity with the father added to the test.
Can a relationship test with grandparents be used for legal or administrative reasons?
Yes, a grandparents DNA test can be used for legal reasons provided a procedure has been put in place and followed. More information regarding legal testing here .
Test participants must provide proof of identity at the appointment and collection by a medical professional. Forensic grandparents test results are admissible in court and can be used for legal and administrative reasons. The results of a grandparents' home DNA test cannot be used legally.
Relationship DNA testing compares the genetic profiles of two or more people to determine a common biological heritage. In general, the test highlights the similarities and differences that make up your genetic fingerprint and evaluates your match rate in order to give you results corresponding to your search for a relationship.
Under no circumstances can this study be established without comparing different individuals , because your DNA is unique and does not contain the genetic profiles of your family, but only its heritage.
The test with the grandparents is a relationship test, because the DNA of two alleged parents will be compared with the DNA of a child.
But other participants can help this research:
- Test between siblings
- Test with grandparents
- Test with uncle or aunt
- Test with cousins
The DNA Relationship Test
Do you want to remove any doubt about your biological origin or that of a loved one? But you don't know which test is best suited to your situation? Follow our guide ! On infotestadn.com we propose to guide you on the possible tests available by putting you in the position of a search for paternity or maternity . It's simple and free, it will allow you to already have solid information before contacting the laboratory that suits you.
Which DNA test to choose?
DNA testing with grandparents can be done with:
- Saliva samples (Sterile buccal swabs)
- Non-standard samples : Like hair, nails, toothbrush...
Be careful, you must follow the instructions and respect the conditions so that the samples provide enough genetic information for your test.
What type of sample is used for the test?
Grandparent Test Participants
- The biological grandfather must participate in the test
For a paternity search between exclusively a grandfather and a grandson, it is advisable to use the Y Chromosome test
- One or more children can participate in the test
Children can be full siblings
Children can be half-brothers or half-sisters
The reliability and authenticity of the test between grandparents and grandchildren depends on several factors:
- The quality of the samples
- Laboratory accreditation
- The choice of test according to family situation
How reliable are the results?
The quality of the DNA will depend on the collection and storage of the samples . It is therefore important to follow the instructions of the laboratory in order to ensure that you receive results.
Accredited laboratories meet the requirements relating to the analysis process, management of resources and equipment, impartiality and confidentiality of information. For a DNA test with grandparents, the laboratory must have an ISO 17025 accreditation .
The reliability of the result depends on the number of genes compared. All the laboratories offer tests on an average of 15 to 22 genes (Loci STR) to carry out the comparison between the participants. Depending on your situation, you have the possibility to ask the laboratory for an extended comparison of the number of loci. The extended comparison improves the precision and therefore the reliability of the results.
The results are presented in the form of a table:
- Each column corresponding to a participant
- Each line has a gene
- The composition of the gene is represented by one or two numbers on each profile
How to read the results of a parentage test?
DNA analysis with grandfather and grandmother is an indirect relationship test. The genetic laboratory tries to recreate the genetic profile of a father or a mother with only the information of the biological parents (grandfather and grandmother). Thus the test is based on statistics and probabilities which play an important role in the interpretation of the results. Participants may have alleles that are different due to random, yet common, inheritance. Conversely, it is not because the alleles are similar that they necessarily confirm the parent in common.
It is possible to obtain inconclusive results .
Checking the participant relationship:
The DNA test for parentage comes with a relationship index . This index in base of 1 expresses the probability of gene in common between the participants. The relationship index is then converted to a relationship percentage.
Parentage test results with grandparents should be interpreted in terms of probability and the parentage relationship index is translated into a percentage that can range from 0% to 99.99% .
- If the index is greater than 1 and your percentage is greater than 90%, the test is positive
- If the index is less than 1 and your percentage is less than 10%, then the test is negative
Parentage Link Results
The Mitochondrial DNA test allows you to compare your DNA with that of your grandmother in order to define a maternal biological link.
Maternal line research
Paternal line research
The analysis of the Y chromosome makes it possible to define whether the grandfather and the grandson come from the same paternal line. By deduction if they are biologically related.
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Discover your results
The Grandparent Parentage DNA Test determines the probability of kinship , between a child (grandson and/or granddaughter) with their grandparents (grandfather and grandmother) .
The test is a genetic comparison in order to establish a biological parentage on the side of a presumed father or mother. The test can be done with buccal samples and non-standard samples. Those tested include a child and a grandfather with the grandmother.
What is a grandparent parentage test?
You can do a DNA test to find out the parentage at home in a private setting . The order can be made directly on the internet from your home in order to receive the sampling equipment at home.
Only, it is still impossible to obtain a DNA test in a pharmacy, moreover only a laboratory with genetic analysis equipment and accredited by international standards can provide the result for a DNA test to know the parentage.
How to do a DNA test between grandchildren and grandparents?
Unfortunately, the answer is no ! Genetic analysis to determine parentage using the genetic profile of a single grandparent is not sufficient to establish accurate and reliable results. Depending on your search for paternity or maternity and depending on the participants available, you can:
Paternity research :
- You can do a Y Chromosome test between a grandfather and his grandson
- You can test the Chromosome X between a grandmother and her granddaughter
Maternity search :
- You can do a mitochondrial DNA test between a grandmother and her grandchildren (boy, girl)
Can I do a test with only one grandparent?
Consent is the agreement you give to the laboratory to use your DNA for the purpose of carrying out a genetic analysis. It is mandatory if you want to do a genetic analysis test. Consent can only be given explicitly by an adult and fully lucid person. This agreement must be drafted after having received information about the outcomes of the test, through a contract or a consent form.
It is against the law to do a DNA test without the person's consent.
For minors, consent must be provided by one of the legal parents.
What is consent for a DNA test?
- 5-7 days using buccal swabs for all participants
- 10 days and more if a participant uses discrete samples
This time is calculated from the moment your samples arrive at the laboratory. The delivery time is not taken into account.
What are the analysis times for a test with grandparents?
The choice of laboratory is a very important step when you want to do a Grandparent DNA test. You should know that not all laboratories offer the same services and depending on several factors it is better to make the right choice.
You must choose a laboratory according to:
- Your family situation and available participants
- The confidence that the laboratory inspires through customer feedback
- The transparency of the company concerning its activity and your expectations