DNA Siblingship Tests
DNA siblingship tests help to determine whether or not siblings share the same two biological parents or not. It is important to note the term “probability”. Unlike a paternity test there are no absolute guarantees, only percentages of probability assigned. Siblingship tests are one of the newest forms of DNA testing on the market, and as such, as the science of DNA evolves and grows the tests will gain higher degrees of accuracies.
When two siblings, or the parents of such siblings, wish to determine if they are true biological siblings (they have the same father and the same mother) the best method available to determine biological siblingship is to test the parents. This will help isolate the chromosomes from each and then map them back against the chromosomes present in the siblings. If for some reason the parents are not available for testing (unknown as in the case of adoption, or deceased) then the DNA testing for siblings can be used to analyze the biological relationship between the two. However, in order to gain the most accurate probability of siblingship from the test, the presence of one parent greatly increases the accuracy of such a test.
Unfortunately siblingships do not provide the absoluteness that paternity tests provide. The results of such a test are not always conclusive, especially when the true parents of the subjects being tested are not available. When the test itself is performed the lab attempts to determine the genetic profile of the subjects being tested. As they are analyzing the DNA of both siblings they examine the type of genetic materials that each sibling has inherited from the biological parents. This genetic material is then used to form a siblingship DNA index.
In the cases where the index is less than 1.0 the two siblings are not biologically related. If the index is over 1.00 then the test shows the probability of biological relationship. The larger the value of the number, the higher the probability the two are biologically related.
In some cases the siblings may only share one common parent, such as the same father but different mothers. In this case a half siblingship index can be calculated based on the genetic material present in the DNA of the siblings. Once this index has been established it is compared to the full siblingship index. The ratio of the two indexes then provides the probability that they are related to only one parent. Again, it is only a ratio and no true determination can be made.
Although there is no absolute certaintity provided when undergoing a siblingship test, the test itself can help provide siblings with an indication of biological relationship.
More often than not the siblingship test is used in cases when the biological mother and father of two individuals is not available or deceased. One of the most common uses of this test is for testing children who may have been separated at birth and placed up for adoption. With the parents unknown, or deceased, it becomes one of the best methods available to help determining if the two children were related at birth.