How to Interpret DNA Results

Although more than 99 percent of Human DNA is similar, certain regions of an individual's DNA are specific to that individual, making it possible to differentiate people based on their DNA. Perhaps one of the most common uses of DNA testing is to determine the likelihood of a certain male's paternity to a child. After the lab receives DNA samples (generally cheek swabs) from the alleged father, mother and child, it performs DNA testing and mails the involved individuals the DNA results in a report.

Instructions

1. Scan your DNA testing report for the phrase "statement of result," or another similar phrase. The testing lab generally indicates exclusion or non-exclusion of the alleged relationship between the male tested and the child.

2. Know that a statement like "Alleged relationship is excluded" indicates that the tested male is unlikely to be the father of the tested child. The lab tests the DNA regions called loci (or if singular, locus) of the mother, child, and alleged father. These regions are unique to each individual. The fragments of the loci are called alleles, and every locus has two alleles, one from each parent. The lab assigns a number for every different allele and compares these numbers among the three individuals tested. For example, if one of the child's locus has alleles designated as 12 and 18, and the mother has the 18 allele, then the 12 allele has to be present in the father. If the tested alleged father doesn't have the 12 allele, he is excluded from being the father of the tested child.

3. Realize that a statement like "Alleged relationship is not excluded" means that the alleged father could be the father of the tested child. DNA testing cannot prove 100 percent that the tested male is the father of the tested child, but rather the lab reports a probability percentage (or likelihood) of paternity. The National Association of Testing Authorities (NATA) requires that this probability percentage be greater than 99.9 percent in order for the accredited lab to report that the tested alleged father is not excluded from being the father of the tested child.

Tips & Warnings

• Deoxyribonucleic acid, or DNA, stores the genetic information necessary for building and maintaining the cells of humans (and other species) in the form of codes that are made up of chemical bases and attached to sugar and phosphate molecules. DNA can replicate (or make copies of itself). Human DNA consists of about three billion bases, all forming ladder-like structures (known as a double helix), which can serve as a pattern for duplicating the sequence of bases. This is critical when cells divide to make new cells that have an exact copy of the DNA present in the old cell.

References

• U.S. Library of Medicine: What is DNA?
• The Genetic Testing Laboratories: How to Interpret a Aprentage DNA Test
• Victorian Institute of Forensic Medicine: DNA Paternity Testing