The relative sizes of the syntenic human (H), chimpanzee (C), and orangutan (O) LR-PCR products were used to determine whether the rearrangement occurred in the human or chimpanzee genome and whether it was an insertion or deletion event. (A) The relative sizes of syntenic human, chimpanzee, and orangutan LR-PCR products compared using gels. (B) The size variation of the human insertion in (A) is barely detectable on gels but is evident in the comparative 21q array data. These LR-PCR products correspond to the rearrangements in Suppl. Table 2 as follows: human insertion = Segment 10 at 161 kb, human deletion = Segment 2 at 301 kb, chimpanzee insertion = Segment 12 at 278 kb, chimpanzee deletion = Segment 76 at 51 kb.