How's it work?

Special locations (called loci) in human DNA display predictable inheritance patterns that can be used to determine biological relationships. These locations contain specific DNA sequences, called markers, that forensic and DNA scientists use as identifying marks for individuals. In a routine DNA paternity test, the markers used are Short Tandem Repeats (STRs), short pieces of DNA that occur in different repeat patterns among individuals. Each person’s DNA contains two copies of these markers—one copy inherited from the father and one from the mother.

 

Within a population, the markers at each person’s DNA location can differ in length and sometimes sequence, depending on the markers inherited from the parents. The combination of marker sizes found in each person represents his/her genetic profile. The laboratory examines a minimum of 16 STR markers to create a genetic profile for each tested person in a paternity, identity, or family relationship test.