FAQ: “Can you help me determine if my brother is really my brother?”
The commonly asked question is followed by a slew of questions from one of our customer service representatives.
1. Do you believe you are full brother’s or half brother’s?
2. Do you believe you share a mother or a father?
3. Are either of your mother's available and willing to be tested?
4. Are any other known family members available and willing to be tested?
DNA relationship testing can be used as an effective tool at proving biological relationships. However, the conclusiveness of test results depends on a number of factor, the most important being the participants’ DNA profiles.
Ex. Sally and Mary believe they are half sisters, and that they share a father. The father is deceased, so a paternity test is not an option. Their mothers are not available for testing because they too are deceased. We have only one option to prove these girls are siblings.
Half vs. Unrelated Siblingship Test – We analyze and compare the DNA profiles of both women. This can lead to a couple outcomes. First, if they both have “common” genes, the results will be inconclusive, showing a probability of relatedness around 50%. Second, if they have “rare” genes, the results will be more conclusive since it is unlikely that unrelated people would share those genes.
If Sally and Mary believed they shared a mother, then we could do Mitochondrial DNA Testing. Mitochondrial DNA is passed down from mother to children, both boys and girls. However, only girls continue to pass it on to their children.
If Sally and Mary were men, then we could do Y-Chromosome DNA Testing. Y-Chrome DNA is passed down from fathers to sons. It continues through the male line, and it is not passed to females.
In Sally and Mary’s case, more participants would help the process, ideally one or both of their mothers. If not their mothers, one of their father’s sisters or brothers would help. The probability of getting a conclusive DNA test result in a half vs. unrelated sibling test is low, but it depends on the individuals being tested. They may share very rare alleles, making it very likely that they are related.