Paternity testing provides a scientific method to establish biological relationships. It analyzes genetic material to determine if a presumed parent is the biological parent of a child. This field’s evolution reflects advancements in understanding DNA’s role in inheritance.
Paternity Testing Before DNA
Before DNA analysis, paternity testing relied on less precise biological markers. The early 20th century saw the ABO blood group system used, comparing blood types. This method could only exclude paternity, not confirm it, due to limited blood types and common traits.
Human Leukocyte Antigen (HLA) testing emerged in the 1970s as a more sophisticated option. HLA testing analyzed inherited proteins on white blood cells. While improving accuracy with a probability of paternity, it remained costly, time-consuming, and required invasive blood samples. It also struggled to differentiate closely related individuals, indicating the need for a more conclusive method.
The Groundbreaking Discovery
In 1984, British geneticist Sir Alec Jeffreys discovered DNA fingerprinting at the University of Leicester. His research revealed unique patterns of repeating DNA sequences (VNTRs or minisatellites). These patterns are highly individual and vary significantly.
On September 10, 1984, Jeffreys observed these patterns, realizing their potential for identification. This discovery laid the foundation for biological identification, offering a tool for forensic science and establishing relationships. The technique quickly demonstrated its utility in resolving disputed parentage and immigration cases.
From Research to Real-World Application
DNA fingerprinting swiftly transitioned from discovery to application. Shortly after Jeffreys’s discovery, DNA evidence confirmed a family relationship in a 1985 immigration case and was used in a 1986 criminal case in the United Kingdom. Restriction Fragment Length Polymorphism (RFLP) analysis was the initial testing technique.
RFLP involved cutting DNA samples with specific enzymes, producing fragments for analysis. Early RFLP testing required large, undegraded DNA samples, and was time-consuming and costly. Polymerase Chain Reaction (PCR) technology, invented by Kary Mullis in 1983, addressed these limitations. PCR allowed amplification of very small DNA quantities, transforming genetic analysis feasibility.
Modern DNA Paternity Testing Standards
DNA paternity testing evolved beyond RFLP to more efficient methods. The current standard uses Short Tandem Repeat (STR) analysis, widely adopted in the 1990s. STRs are short, repeating DNA sequences (2-6 base pairs) that vary in repeat numbers among individuals.
Analyzing multiple STR markers provides a highly discriminating DNA profile. This method improved the accuracy, speed, and accessibility of paternity tests, with results typically showing a probability of paternity of 99.9% or higher. Modern tests often use non-invasive sample collection, like cheek swabs, making the process convenient and reliable. The core principle of comparing inherited DNA markers remains, with advancements making testing efficient and reliable.