Low-copy repeats (LCRs) flanking the Charcot-Marie-Tooth disease type 1A duplication (CMT1A-REP) and the Smith-Magenis deletion (SMS-REP). (a) A somatic cell hybrid panel with a chromosome 17p ideogram (left) and vertical bars representing the regions retained in the individual human hybrid cell lines listed at the top. (b) Southern hybridization with a CMT1A-REP probe. There are two cross-hybridizing signals in human genomic DNA (lane 1), none in the mouse and hamster genomic DNA (lanes 2 and 3), and the same two in a monochromosomal hybrid (MH22-6, lane 4) retaining human chromosome 17. Both copies map to the CMT1A duplication region at 17p12. This is interpreted as showing that there are two copies of CMT1A-REP, both mapping to the CMT1A duplication locus, and both of which evolved late in the mammalian radiation as they are not present in mouse or hamster . (c) Three copies of SMS-REP (arrows) on chromosome 17 . We used the term REP because at the time my laboratory was working with prokaryotic repeated sequences (REP) and had developed a technique we referred to as rep-PCR [157, 158].