With a DNA Sibling test, it is possible to determine whether siblings share either one or bother parents.  It is therefore possible determine what grade of relationship exists in between siblings, whether they are half (Sharing only one parent) or full siblings (sharing both parents.  It is even possible to determine whether they share none at all.

Siblings DNA : How much DNA should Siblings Share?

Sibling tests are based on a statistical analysis of two persons DNA.  It is difficult to determine exactly how much DNA siblings should share.  It is calculated that roughly they should share around 50% of their DNA in order to be full Siblings – Both parents in common.  The amount of DNA siblings share can vary, depending on what common DNA they got from their parents.  There are instances of full siblings sharing very little DNA but there are siblings that could also share 100% of their DNA , like identical twins.

Sibling testing like other tests that are designed to solve diverse familial relationships, fall under the category of Relationship testing.  Other types of relationship genetic testing involve Aunts/Uncles and Nephew/Niece, Cousins and Grandparents.

The fact that siblings have a relationship that is quite close in proximity makes sibling testing quite precise.

With other types of relationship testing, for example with cousins, it turns out that it’s more difficult to determine the relationship- Cousins of first order share only about 25% of their genetic makeup.  Half siblings also share about 25% of the genetic make up.  That is why it is not always possible to determine the difference in between cousins and half siblings unless the samples of a known parent are introduced.

 How is the sibling test carried out?

The way the Sibling DNA test is normally carried out is by means of a saliva sample of the participants.  This is collected by means of a mouth swab that is rubbed inside the mouth.  A saliva sample is the most ideal sample to use for DNA testing as it is easy to collect, has a high presence of cheek skin cells with DNA information and has the ability to preserve itself for a long time, meaning that it is also ideal to send through the post.  Everything for the sample collection is normally provided to you in a testing kit sent out in the post.  The sibling test is normally carried out to determine whether siblings share a or two common parents.  In most cases the mother is already known and could be either in common or there could even be two mothers.  The accuracy of this test is not as high as a paternity DNA test.  It is therefor highly recommended to proceed with a paternity test when possible in order to determine if the father is the father of one or more siblings.  It is only suggested to do this test when the father is not available.  Including the mother’s sample always helps in achieving a more definite answer as her DNA information help scientists decipher with more exactitude the origins of the siblings DNA.