Carrying out a DNA Test between Brothers and Sisters

12 Aug 2017

There a number of DNA tests which can be done between siblings. We shall briefly look into the most important ones and provide the information about how to go about these tests and anything else that is important for those wishing to do a sibling DNA test to know.

Sibling tests are a type of relationship test. There are a number of sibling tests, namely these are:

• Y chromosome test
• X chromosome test
• Full STR sibling test
• MtDNA test

As the name implies, a DNA test for siblings is specifically done analyzing the DNA of siblings. Many times the test is required in order to establish whether siblings share a common biological parent, for example, two half brothers want to know whether they share the same father.

Generally, the most common scenario is the desire for siblings to determine paternity. Normally, it is necessary to do a sibling test because the father is not available for the test- the siblings in question may not actually want to tell the father about the DNA test or the alleged father may have passed away.

The type of DNA testing for Siblings

The Y chromosome test is done solely between males that want to know whether they share a common paternal line. The test is highly accurate and reliable and will very much provide a yes or no answer. However, if the tested males might still be related through the male line (for example first cousins) the test will not tell you very much as the two alleged fathers are related.

The X chromosome test is done between females who wish to know if they share a father. For an X chromosome test, it is always strongly recommended to include the mother’s sample. The test works best when the siblings have different mothers. If they have the same mother, it is rather more difficult to determine whether the X chromosome shared was inherited from the mother or from the father. Again, the mother’s sample is very important.

In cases where the siblings are male and female or when the mother’s sample is not available, a full siblings test will be needed.

An MtDNA test is done to confirm whether two or more people share a common maternal line. In some cases adopted children may be interested in this test. If two people are related through their maternal line the test will show nothing more than what they already know.

DNA testing for siblings can answer countless questions about the existence of biological relationships between siblings.