DNA LOCI

Instead, all labs pin-point various 'regions' (technically called loci), to discover the type of DNA each person tested has in these selected regions and revelling to us their biological relationships.

The more regions tested, obviously the higher the accuracy of your test.

The most commonly tested loci tested are called the 13 CODIS regions. These loci were adopted as the 13 internationally accepted regions of DNA to test in 1986.

Today most paternity labs are using these 13 loci, although some labs are testing as few as 9 loci, most have adopted 16 loci (CODIS + 3) to provide an accuracy that they are comfortable with.

Loci used for paternity or identity testing are not areas in genes, but are actually areas of DNA between the genes. These areas of DNA between the genes are often highly variable (polymorphic) and therefore usually different between unrelated persons.

The reason these loci are so highly variable is because if there is a mutation in this area it will not affect any of your genes, and hence will not affect your abilty to function and reproduce normally.

Hence, over many many generations, these mutations have persisted in the population, eventually leading to areas of DNA that have many different possible combination.