DNA Direct: Your Genes in Context

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Paternity & Family Tests

Related Genetic Tests

DNA Archive™

Convenient at-home DNA storage. New SampleMatrix™ technology.

Price: $225.00

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Pre-test & Post-test Consultation

Our genetic experts can counsel you before and after testing.

Price: $250 per hour

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Sibling Testing

What does this test tell me?

A sibling DNA test can help establish a biological relationship between two people who may share one or both parents. This test can be used when other biological relatives (like parents or grandparents) aren't available for DNA testing. For example, it can be used to confirm a shared father, when the possible father isn't available. However, if the paternal grandparents are available, grandparentage testing is more reliable than sibling testing.

Sibling tests compare the DNA from two people to see how much of their DNA may have been inherited from a common father.

A full-sibling DNA test is for people who share the same biological mother and want to know if they also share the same biological father.
A half-sibling DNA test is for people who have different mothers, but want to know if they share the same biological father.

This sibling test begins by looking at 16 different DNA markers (unique sequences) in the DNA of each person tested. Everyone has a pair of each of these DNA markers: one inherited from the biological mother and one inherited from the biological father. The test compares each of these markers between the possible siblings and the mother(s) (if available). Half of a child's DNA markers should match the mother's and the other half should match the father's.

Sibling testing is more complicated than paternity or grandparentage testing, and there may be additional charges and time required for some cases. It usually isn't possible to definitively say that two people are siblings instead of being biologically related in some other way. The laboratory reports a number (called a "Combined Sibship Index") that tells you the genetic odds that the two people tested are, indeed, full or half siblings.

Who needs to be tested?

Two potential siblings (no more than two at a time)
If possible, the siblings' shared mother (if related through the mother) or both mothers (if possibly related only through the father)

Although the mother(s) aren't required to submit a sample, having those results allows the laboratory to exclude the markers contributed by the mother(s) and focus on the father's contribution for each child. This increases the test's reliability. If the mother(s) aren't available, the laboratory may have to test more than 16 markers to reach an acceptable level of certainty about the sibling relationship. This may cost more and take more time.

How does testing work?

With DNA Direct, you can order online, collect a painless cheek swab sample at home for any people that need to be tested, and receive your results anonymously. Test results are ready 14 business days from the time the laboratory receives DNA samples from all participants.

After placing an order, you are sent a self-collection kit that includes cheek swabs, return envelopes, and instructions. It is important to follow the instructions carefully. To collect each DNA sample, you rub a cheek swab up and down the inside of the person's cheek. The laboratory extracts the DNA from the cheek swab and analyzes it using standard laboratory procedures.