Proving Fatherhood with Paternity Test DNA

The goal of this page is to help you understand paternity test DNA, just one type of DNA testing covered on this web site. I went through this testing with my alleged father and am happy to share what I learned through research and personal experience.

When a child is born, there is rarely any doubt about the mother’s identity. She must be present…and the birth is usually witnessed and recorded by medical staff.

The father, however, played his role about nine months earlier. Since pregnancy is not immediately obvious, many situations arise where one or both parents may not be certain who the true biological father is.

Issues such as child custody and child support are just some of the reasons for paternity test DNA.

The New Science of DNA

DNA, which stands for deoxyribonucleic acid, is found in all living things. This is the main molecule responsible for heredity, determining which traits pass from parents to children. Most of our DNA is in tightly coiled strands called chromosomes. There are 46 chromosomes in a human cell.

If you could unwind each chromosome and place them end-to-end, you would have a long, double-stranded helix that looks like a twisted ladder. That’s the common visual to represent DNA. The arrangement of DNA molecules, called the DNA sequence, provides the instructions for our physical characteristics and body functions. These instructions are found in segments of the chromosome called genes. And the science is called genetics.

DNA and Paternity

Each one of us inherits (randomly) 23 chromosomes from our father and another 23 from our mother. Chromosomes are found in certain areas of the body, including white blood cells, cells inside our cheeks, and in saliva and hair roots. DNA collected from any of these sites can be used to identify people and determine relationships.

Paternity test DNA examines certain loci (regions) on the chromosome. Comparing the DNA sequence of a child to that of an alleged father can show if the child’s DNA was derived from that man or not. When possible, the mother should also be included in the testing, since she can provide additional genetic information and simplify the testing process. But paternity can still be checked without the mother’s DNA.

Sample Collection

When my alleged father and I were compared, the lab tested our blood. Today, most companies collect DNA samples by rubbing what they call a “buccal” swab inside your cheek. It’s simple and painless. If a court is involved, paternity test DNA samples will have to be collected at a DNA testing center. If not, you can use a home DNA test and mail in the samples.

Lab Tests and Reports

The first step with paternity test DNA is to see if the man can be excluded. There are certain genetic markers that a father MUST transmit to his children. Similarly, there are certain markers in the child that MUST come from the father. If any of these fundamental requirements are not met, the man cannot possibly be the father.

If a man cannot be excluded, a probability of paternity is calculated and reported. The probability cannot be 100%, since every man in the world is not being tested. But a probability value of 99.99% or higher eliminates most other men from being the biological father. This virtually proves that the tested man is indeed the father of the child.

Other Considerations

One limitation to be aware of is that identical twins' DNA is “identical.” If a man has an identical twin, paternity test DNA cannot determine which brother was actually the child’s father. Fraternal twins, on the other hand, are no more alike than other siblings. But if more than one man from the same family is a possible father to the child, then all of the candidates should be tested.

You may see mentions of other blood testing techniques that don’t use DNA. These are more powerful than a simple blood type analysis. But they are less accurate than paternity test DNA. If you’re going to get a paternity test, insist on one based on DNA.

My Recommended Test Lab

I recommend DNA Findings for traditional paternity testing, especially if you need a legal paternity test.

If you only need the information for personal knowledge, I suggest you look at 23andMe or Family Finder or AncestryDNA. Any of these genetic genealogy tests can clearly identify parent-child relationships as well as uncles, grandparents, siblings, half siblings, and cousins. Plus, you can measure your ethic ancestry and discover biological cousins who can help you build a family tree.

You can buy two home test kits from any of these three companies for less than $200.





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23andMe now offers two versions of it's DNA test. The Ancestry-only version is just $99. The Health + Ancestry version that includes some FDA-approved health test results is $199.


If you already have results from another autosomal DNA test, you may be able to transfer into Family Finder for free.