More information about the X chromosome test

An X chromosome test will in such cases allow the tested parties to establish whether they are:

  • Half sisters or full sisters
  • Half sisters or not sisters at all

The cost of an X chromosome test for two sisters is £329 with you results ready in 15 working days. You can proceed to order your test online or if you have any questions you can contact us or request a call-back free of charge!

How accurate is an X chromosome test?

The X chromosome test is based on the fact that females receive one X chromosome from the mother and the other from the father. In the case where two sisters have different mothers, we can do an X chromosomes test without the need for the sample of the mother. The X chromosome test will establish whether they share the same X chromosome. If they do, it means they share the same father.

Two sisters that share the same mother and want to establish whether they are full siblings or half siblings will need to include their mother’s DNA sample alongside their own to be able to conclude the test. We will need to map the X chromosome pattern in the mother’s DNA sample and exclude this from this from the analysis. We can then compare the remaining X chromosome pattern on the sisters’ DNA to look for a match. If the X chromosome profile match is confirmed, this would indicate that they likely inherited it from the same father. If the mother’s sample is not available then a siblings STR test is recommended.

Paternal grandmother and granddaughter

The X chromosome test can be used between paternal grandmother and granddaughter as they 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 and require no other samples in this particular case.

Carrying out a paternity test

It is important to note that we always advise doing a home paternity test where possible rather than the X-chromosome test as the testing procedure for the X chromosome is more complex and thus, more expensive.  Results for a paternity test are also more conclusive as we establish paternity by directly comparing the DNA of the alleged father and child.

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