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DNA Paternity Test – How to Make Sense of the Results

The results from your paternity test are finally in, but what is an allele and how do you interpret the results?  Where did they get the 99.9% probability from?  Paternity test results can be confusing to understand, but here’s what you need to know.


Twenty-two genetic markers, which are known for being highly variable between individuals, are studied in order to conduct a paternity test.  Each of the DNA markers contains two alleles, one inherited from the biological mother and the other from the biological father. The paternity test compares these markers between the alleged father and the child in order to determine paternity.  An example paternity test result is shown below:




paternity dna test report

The highlighted numbers indicate the alleles that the child inherited from the alleged father.  Each marker is also assigned a Paternity Index (PI), which is the statistical measure of how strongly a match at a marker indicates paternity.  The Combined Paternity Index is all of the PI numbers multiplied together, indicating the overall probability of the alleged father being the biological father, relative to any other random man from the population of the same race.  If the probability of paternity is reported as 0% probability, the alleged father is excluded as the biological father.  If the probability of paternity is at least 99.9%, the alleged father cannot be excluded as the biological father.

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