Figure 1: The general structure of the D1S80 locus is that of a monomeric type VNTR consisting of four 5′ repeat units (A-B-C-D) and seven 3′ repeat units (H-I-J-I-I-L-G) that are constant (motifs), with variable number of repeats in between. These two motifs are essentially identical in almost all alleles sequenced in all population groups so far (data not shown). There is a 132 base pair 5′ flanking region which includes the forward PCR primer (P1) and a 32-base pair 3′ flanking region which includes the reverse PCR primer (P2) sequence. The two-flanking restriction site polymorphism, HinfI (GANTC), 58 base pairs from the 5′ end of the primer, and the Fnu4HI (GCNGC), the first base after the last repeat are shown by arrows.