Relationship DNA Test Guide

By: Erin Hasinger, Tests.com

DNA tests can be used to determine familial relationships. Relationship DNA testing can help one learn more about their maternal or parental lineage, paternal relatives, grandparentage or siblingship. Often, relationship DNA testing is done when one’s biological father is not confirmed or when he is unavailable for a DNA test himself. Relationship DNA tests cannot conclusively determine maternity or paternity, but can help find one’s biological maternal and paternal relatives.

In nearly all relationship DNA tests, DNA from the mother is requested in addition to that of the child and other relatives for exclusionary purposes. Once the mother’s half of the DNA has been excluded, analysis is far easier, and also more cost-effective.

Paternal Lineage

A paternal lineage test analyzes patterns of the y-chromosome in DNA to determine if two males are related through the same paternal family line. Only males carry the y-chromosome, and the chromosome is passed from father to son over time with few changes. Analysis of the y-chromosome in suspected relatives helps to determine if they come from the same paternal line.

Maternal Lineage

Maternal lineage DNA tests use mitochondrial DNA patterns to determine if two or more people are related through a maternal family line. Such a test is generally used when maternity is not known, but rather suspected. Maternity cannot be confirmed through this particular test, but relationship to maternal relatives can. The mitochondrial DNA test is specific to testing maternal relatives because only women pass mitochondrial DNA to their children. In this analysis, mitochondrial DNA sequences are compared.

Paternal Relatives

When one’s suspected biological father is not available for a DNA test to confirm paternity, a relationship DNA test can be used on the alleged father’s relatives. The DNA of the child and the relatives are compared to determine if there is a genetic relationship. The closer the relatives are in relationship, the greater likelihood of more conclusive test results. In this type of test, it is necessary to test the child’s mother so that her half of the DNA can be excluded. Generally, at least three relatives are also required for testing.

Grandparentage

Similar to testing paternal relatives, a grandparentage DNA test can be done to help determine paternity. A grandparent DNA test looks at the DNA of the paternal grandmother, paternal grandmother, mother and child. Once the mother’s half of the DNA is excluded, the remaining half is compared to that of each of the grandparents.

Siblingship

In this test, DNA from suspected siblings is tested to see if they share a common father. Two types of tests are available – one for siblings with the same mother and one for those who do not. When the mother is available, her DNA is requested for the test so that half of each sibling’s DNA can be excluded during testing.

DNA is collected for relationship DNA testing using a buccal sample, which simply means a cheek swab. A cotton swab is swiped against the inside of one’s cheek. The DNA in the collected cells is then analyzed. If the DNA sample is collected in a laboratory facility, a professional will do the collection, but home test kits are also available in which one can do the cheek swab and then mail the cotton swab back to the lab in a provided container.

Tests are available from labs worldwide; those seeking a DNA test should work with a lab accredited by the American Association of Blood Banks.

Analysis times vary. When the mother’s DNA is available for exclusionary purposes, testing may be expedited. Generally, test results are made available within three to fourteen days.

Costs also vary depending on the type of test, number of participants and location of the laboratory. Test costs range from around $200 to $1,000. Some tests are less expensive when the mother’s DNA is tested because less analysis is required.

For more on relationship DNA testing, see the Relationship DNA Test Directory.

Sources: DNA Diagnostics Center, Easy DNA