What is the principle behind a paternity test using DNA?

The question of paternity has always been of paramount importance for individuals, families, and society as a whole. Scientific advancements, particularly in the field of genetics, have made it possible to use a precise method to determine paternity: the DNA paternity test. But what exactly does this test entail? What is the principle behind this procedure, often regarded as an undeniable source of truth? Let's take a closer look at how this revolutionary method works.

How does genetics help determine paternity?

The DNA paternity test is based on a simple yet powerful principle: every individual inherits their genetic material, DNA, from their biological parents. DNA, or deoxyribonucleic acid, is a molecule present in every cell of our body, carrying the genetic information that determines our physical characteristics, inheritable traits, and other aspects of our biology. DNA is composed of segments called genes, which contain instructions for the production of proteins and other cellular components. These genes are organized into structures called chromosomes. Humans have 23 pairs of chromosomes, one of which determines sex: females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). When a child is born, they inherit half of their DNA from their mother and the other half from their father. This genetic transmission forms the basis of the DNA paternity test.

How does the DNA paternity test work?

  • Sample Collection: The first step in the process is to collect DNA samples from the presumed child and the presumed father. This can be done by taking a saliva sample using a buccal swab or by using other non-invasive methods to obtain cells containing DNA. 
  • Sample Analysis: The collected DNA samples are then analyzed in a laboratory. Specialized laboratories typically use techniques such as PCR (polymerase chain reaction) or RFLP (restriction fragment length polymorphism) to amplify and analyze specific segments of the DNA. 
  • Comparison of Genetic Profiles: Once the samples are analyzed, researchers compare the genetic profiles of the child and the presumed father. They examine specific genetic markers present in the DNA and look for similarities between the two profiles. These markers are sequences of DNA that vary from person to person and are inherited in a predictable manner. 
  • Calculation of Paternity Probability: Based on the comparison of the genetic profiles, a paternity probability is calculated. This probability is expressed as a percentage and indicates the likelihood that the presumed father is indeed the biological father of the child. A high paternity probability, generally above 99.9%, is considered conclusive.

What is the reliability and accuracy of the DNA paternity test? 

The DNA paternity test is widely recognized as an extremely reliable and accurate method for determining paternity. With an accuracy of over 99.9% in most cases, this test is often considered irrefutable proof of biological paternity. However, it is important to note that the test's reliability depends on the quality of the samples collected and the accuracy of the analyses conducted in the laboratory. Errors can occur if the samples are contaminated or mishandled, highlighting the importance of using specialized and accredited laboratories to conduct the test. The quality of the samples and the accuracy of the analyses are fundamental to ensuring the reliability and credibility of DNA paternity tests. By addressing these aspects, specialized laboratories can provide precise and reliable results, offering an undeniable source of truth in often delicate and complex situations.


The DNA paternity test is based on the fundamental principle of genetic inheritance. By comparing the genetic profiles of the presumed child and the presumed father, this test can determine paternity probability with great precision. Through this method, individuals can obtain definitive answers regarding biological paternity, providing an undeniable source of truth in often complex and emotional situations.