Grandparent DNA Testing
Testing Biological Relationships

Genetic Grandparent testing

DNA Grandchild and Grandparents

Biologically Related?

Grandparent DNA Testing


What Is A Grandparent Test?
Why Do People Take Them?
Types Of Tests
How To Carry Out A Test
How Much Do They Cost?

Guide To Genetic Tests
For an overview, read:
Genetic Testing

What Is A Grandparent Test?

Also known as grandparentage testing, this is a DNA test to determine the biological relationship between 2 alleged grandparents and a child. It is most commonly performed when the alleged father is absent. Biologically both grandparents contribute equally to their son's DNA. The son in turn passes 50 percent of his DNA onto his child. A grandparentage test can establish a relationship by determining if half of your child's DNA comes from the alleged grandparents. Ideally the mother's DNA should also be taken as this makes it easier to eliminate her 50 percent DNA contribution and to highlight the father's or grandparent's DNA. A motherless test however is also possible if the mother is not willing or available to participate. Of course, if the alleged father is available paternity testing is another alternative.

Why Do People Take Them?

According to the American Association of Blood Banks’ (AABB) Relationship Testing Program Unit just over 414,000 relationship tests were carried out in America in 2008. This also includes other types of relationship tests such as:

Sibling DNA Tests
Twin DNA Testing
Y Chromosome DNA Tests

This was a significant increase from 77,000 in 1988. The most common reason to take a grandparentage test is to prove paternity of a child in the absence of the alleged father. This may be for inheritance reasons, social welfare payments or simply to resolve family disputes. If the grandparents had more than one son, all sons may need to be tested if legal disputes are involved. The other important use is for immigration. DNA tests are required for most visa applications to prove relationships with citizens already established in the U.S. It is important to note that non-legal paternity or grandparent tests will not be accepted by the Department of Homeland Security. A so-called chain of custody needs to be established whereby a trail of paperwork is generated. Reputable laboratories such as DDC (DNA Diagnostic Center) offer 'legal' tests which are AABB approved and accepted by the U.S. government. Given the extra administration involved legal tests are always more expensive than non-legal. For those people who simply wish to satisfy their own curiosity and do not plan to use the results in court, a non-legal test is perfectly adequate.

What these tests are NOT used for is checking for a genetic disorder or illnesses. If this is a concern please see our articles on:

Genetic advisors: professionals who can explain all the various testing methods available.
Genetic testing before pregnancy: for couples who would like to assess their risk of having children with birth defects.

Types Of Tests

Duo Grandparentage

This analyses the DNA of both grandparents, the child in question and one parent of the child. The parent of the child is optional, but if available can improve the overall accuracy. Results are normally 99 percent accurate.

Single Grandparentage

This analyses the DNA of one grandparent, the child in question and one parent of the child. Again the parent of the child is optional. If only one grandparent is available the results are substantially less accurate. This is because each single grandparent only passes 25 percent of their DNA onto their grandchildren. A low result would indicate that the child is either not a grandchild or that the child's key genetic markers come from the missing grandparent. For this reason, it becomes impossible to rule in or out if the child is their grandchild. Results can be anywhere between 1 and 99 percent accurate. If a grandparent is dead or missing some labs offer further testing possibilities by using Y-STR, X-STR or Mt-DNA tests. For example DDC have developed trademarked product PlatinumPlex which tests for 27 markers instead of the average 16. This increases the power of the test, however it also increases the price by around $100.

Y-Chromosome Testing

This test is only an option for males. It checks the relationship of grandfather and grandson. This may be an option if the grandmother is not available for testing.

In all cases, accuracy is better if the DNA of the mother can also be tested.

How To Carry Out A Test

According to the AABB 98 percent of relationship tests use buccal swabs. In rare incidences blood, bone or hair samples are used. In both legal and non-legal instances the actual test is the same, involving swiping a cotton tipped buccal swab on the inside cheek and returning the sample to the laboratory in an envelope provided in the testing kit. A non-legal test can be bought over the internet and carried out in the privacy of your home and posted back to the lab. They usually take about 5 to 7 working days for a result.

A legal test however requires documentation of chain of custody. To meet chain of custody requirements you must:

1. Arrange a neutral party such as a local lab or hospital to take the sample.
2. Adults will be asked to present a government issued proof of identity.
3. Children will need a birth certificate or social security card.
4. All parties will be photographed and finger printed.
5. A Client Identification and Consent Form will need to be completed and signed.

The collector will then return the samples to the DNA lab. Results are normally emailed, posted for given over the phone within 10 to 14 working days.

How Much Do They Cost?

Costs will depend on how many people are to be tested and whether or not a chain of custody (legal) needs to be established. Below is an average estimate of costs.

Type Non-Legal Legal
Single Grandparentage $550 $650
Duo Grandparentage $450 $600
Additional Markers Tested $100 $100

  Related Articles on DNA

For more on relationship testing, see the following:

Genetic Testing During Pregnancy
Ancestry Gene Tests
Can a paternity test be done without the father?
Genetic Testing for Breast Cancer
Paternity Test Kit

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