Known as PCR (polymerase chain reaction), the procedure is used in comparing samples of the child’s DNA with that of the alleged father. Since the child’s DNA is a fairly equal combination of DNA of his parents, excluding the DNA of the mother gives us a genetic profile of the biological father.
However, before science knew how to isolate DNA, blood samples were the standard in a variety of testing methods in the past to help exclude potential fathers.
All had varying rates of success. Back in the early 1900s, blood testing was the first method used in determining paternity.
Blood typing
During the 1920s, scientists were able to identify one blood type from another. Just like DNA, a child’s blood type is a combination of that of the parents.
The blood type is determined by the proteins in the red blood cells known as ABO antigens. These antigens are the reason that you must have a specific blood type during transfusions.
It also limits the blood type of your offspring. Using these blood markers and characteristics, scientists later learn the logic and the possibility of excluding potential fathers if the blood types do not match.
However, blood typing alone cannot establish paternity since unlike DNA., blood types are not individually unique. Nevertheless, it had allowed specialists before to narrow down the list of putative fathers by excluding around 30% of potential candidates.
Serological testing
Still later, science discovered other proteins in the blood that are more group-specific than the ABO antigens themselves.
Following ABO comparison, science discovered other proteins in the blood that are more group-specific than the ABO antigens themselves. The proteins (Rh, Kell and Duffy blood groups) give scientists the ability to exclude potential fathers at a slightly higher accuracy rate of about 40%.
Just like ABO, serological tests still cannot identify the father with enough certitude, although it can exclude those that do not possess the correct blood groups.
HLA testing
In the 70s, another breakthrough was made. Scientists isolated another set of proteins called HLA (human leukocyte antigens).unlike basic blood type proteins, the HLA proteins are found in all the body’s cells except the red blood cells. They are used by the body’s immune system to detect foreign bodies and fight infections.
While still not as reliable as DNA testing, HLA can exclude potential fathers with up to 80% accuracy ratings. Unfortunately, HLA testing requires a larger blood sample.
However, blood sample comparisons are still relevant. One instance is if a child’s blood type does not match that of a putative father. From there, things are already clear and there is no need for an expensive and emotional paternity suit and DNA tests.
