Above I scanned three systems (plus amelogenin) from a paternity case. The top row is the allelic ladder-this represents all know alleles for the three STR's. The numbers under each peak represent the number of pattern repeats in that system. The XY represent the sex marker. The second row is the positive control it will always be the same (if not the run is invalid).

The three remaining rows are the alleged father (AF), child (C), and mother (M).

Looking at the child's sample you can see that child is male and got his:

• 14 from his father and a 12 from his mother in D8
• 29 from his father and a 28 from his mother in D21
• from his father and a 19 from his mother in D18

If we looked at the remaining systems, we would see that they all matched. Paternity calculations are based on the pattern of shared alleles and frequency of the obligate paternal allele...the calculation looks like this: