What is a Siblingship DNA Test?
Over the past few weeks, we have discussed heavily on the different types of DNA testing that is out there and the different areas they are used in to help determine either paternity, ancestry, or within the criminal justice system. One area we have not touched base on and is used less than the others but should still be understood is in the cases of a siblingship DNA test. You can probably guess what these tests are used for. This DNA test is used to help determine whether or not two or more siblings are related and the probability of full siblingship, half siblingship, or unrelated. If the results show that the two individuals are related, then they could share either both or only one of the parents.
A siblingship test is analyzed very similarly to that of a paternity test. Results are studied for Short Tandem Repeats which is where DNA segments repeat themselves. These segments are passed down from parent to offspring. These patterns are then compared to the two individuals taking the DNA test to see if they have similar repeats in their DNA. The patterns will help determine if you are in fact related and can help determine whether full or half siblingship.
One thing that is different from paternity or maternity testing is that siblingship is slightly less conclusive. Even if siblings are related, their STRs markers can be fewer than that of parent and child because they vary when they are passed down. Because genes are passed down from both parents to the offspring, it is uncommon that siblings will share the exact DNA and STR markers which is why when taking a siblingship test, you do not receive the most conclusive results compared to that of a paternity/maternity test.
This may sound discouraging and not necessarily the most certain, but there are factors that can help in the conclusiveness of a siblingship test. One way to help the results be more conclusive is to also have one known or shared parent also take a test. This gives the testing company another set of genes and STR markers to compare the results to which will ultimately help determine a more conclusive set of final results. Another factor that can help with better results is setting how many STR markers are being analyzed. No matter how many family members you can get to take the test, setting the highest amount of STR markers that will be analyzed will give you clearer results. This amount will vary from company to company, and you should ask for the highest amount that the company you choose will test for.
It may seem crazy to think that you would need a DNA test to determine whether you and another individual were brother or sister, but for those who have been long-lost over the years, this type of testing can be extremely useful.
