More about the X chromosome test

An X chromosome test can be done to confirm whether 2 or more females from different mothers share the same father. In cases where females share the same mother, an X-chromosome test can still be done; however, this test is only possible if the mother is available for testing. If the mother is not available for testing, then you will need to do an STR siblings test.

Why do I need the mother’s sample?

The reason for needing the mother’s samples is the following: Any female inherits one X chromosome from their mother and one X chromosome from their father. If two siblings share the same mother, thereby being at least half siblings from the mother’s side, an X-chromosome test will not be able to determine which X chromosome was inherited from the mother and which from the father. Having the mother’s DNA means we can exclude her share in genetic inheritance and concentrate on matching the X chromosome from the father’s side.

X chromosome testing: Paternal Grandmother and Granddaughter

The X chromosome test can be used between paternal grandmother and granddaughter as they must share one X chromosome. This shared X chromosome is the one that the grandmother passed to her son and he, in turn, passed to his daughter. We only need DNA samples of the paternal grandmother and granddaughter for this test. We require no other samples in this particular case.

How do I collect my DNA samples?

You can collect your samples with our home DNA testing kit. Our kit includes everything you need to collect your DNA samples. This includes:

  • 4 mouth swabs per person tested
  • Instructions (which include precautions and the step-by-step sample collection kit)
  • DNA sample consent forms
  • Self-addressed envelope

We provide a full explanation of the procedure on our sample collection page.

Pricing and results

The X chromosome test is priced at $499 for the testing of two females. Results will be available in only 15 working days.

Full siblings testing

X chromosome testing can only be carried out if the individuals are female. In cases where brothers and sisters are taking part in the test and want to know if they share a common father, we suggest a siblings DNA test.


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