The 1970s brought on HLA typing, which does not require DNA and was used for paternity testing. Later PCR (polymerase chain reaction) was developed. This test eliminated 80% of the male population but cannot distinguish between related alleged fathers.
HLA (Human Leukocyte Antigen) is a protein found in white blood cells and any individual has quite a unique set of HLA proteins inherited from their parents.
This testing had drawbacks: very large amounts of blood were needed meaning that babies had to be over 6 months old to be tested.
Using DNA to establish paternity was logically only possible after the discovery of the structure of DNA in the 1950s.
It was not however, until the 1980s that DNA was used to establish paternity.
In the 1980s these tests became available with the possibility of including a father as the biological dad with an accuracy of 80% or sometimes even 90%. The procedure is known as RFLP (restriction fragment Length polymorphism). The testing required blood samples but an issue was that considerably large DNA samples were needed for scientists to work with. The processing time was also lengthy and thus, the method has gradually become disused as a better method was invented.
DNA Paternity Testing in the 1990s
PCR (Polymerase Chain Reaction) is the method that is used nowadays for paternity DNA testing. Scientists can work with very small quantities of DNA because with PCR they are able to replicate and make thousands of copies of the DNA and thus, have lots to work with. The DNA sequencing process with this method takes only around 2 hours. The process involves a reaction in which DNA is heated to 94 Celsius. An enzyme is then used (DNA polymerase) to assist in the replication and amplification of the DNA. The enzyme reads the code and then uses it as template. This is essentially the process very simply put.
Paternity testing has become extremely accurate with PCR; the HLA has become obsolete.