Understanding Your DNA Test Results

The results in simple terms

The DNA test results will either include or exclude a given person from being biologically related to another person. In paternity testing, the tested putative father is father is excluded as being the biological father when he shares an insufficient number of genetic markers with the child; in this case the probability of paternity reads 0% in your result. When alleged father and child share a sufficient number of genetic markers, he is “included” as the biological father; the probability of paternity in this case reads 99.99%.

The combined paternity index or CPI

The Combined Paternity Index (CPI) is a scientific algorithm used for DNA comparisons. When a given person’s DNA undergoes analysis, the scientists examine what are referred to as the genetic Loci or very specific locations on their genetic makeup. These loci help accurately confirm or exclude the genetic relationship between the people tested. PTL analyses 23 genetic loci, including gender markers, in order to run a complete and scientifically valid DNA test which adheres to international testing standards. The actual CPI of a test subject is the coincidence, or similarity level, of one person’s 21 genetic markers in comparison with another. It is done by multiplying all 23 paternity indexes that are derived for every one of the 20 genetic loci we test. Using these values we can proceed to calculate the probability of paternity. This figure expresses how many times more likely the alleged biological father is the real father of the child when compared with an untested male in his same ethnic group. In this way DNA tests can positively determine genetic relationships to a startling accuracy of 99.99999% when testing for paternity.

Your DNA test results

During the DNA analysis at our accredited laboratories, the loci required will be extracted, amplified and examined using a process of analysis known as PCR or polymerase chain reaction. This biochemical technology in molecular biology enables us to work with very small DNA samples and provide highly accurate results.

On the actual DNA test report sent to our clients, there will be two columns. On the left hand portion of the report will be the actual loci tested – all 20 of them. For each Loci identified, there are two numbers presented. For example, if the child’s numbers for a particular locus are 12 and 18, the number 12 size loci will be inherited from one side (maternal or paternal) and the other number 18 from the other (paternal or maternal). PTL will be able to determine which locus was inherited from which parent by comparing the profiles of two or more people. Thus, if the alleged father has numbers 18 and 2 for the same locus, we can conclude that the child inherited the number 18 locus from the father and the 2 from the mother.

Whilst we do not need to have the mother’s sample to accurately conclude a paternity test. We always recommend testing the mother’s sample because this will help us have a more thorough analysis. We can extract the mother’s DNA profile and include it in the comparison of genetic markers, helping us provide a more accurate result. In some exceptional cases of genetic mutations, the mother’s sample may become indispensable to the analysis. Contact us for more information.