Large-scale rearrangements mediated by 8p23.1 repeats. Schematic idiograms of the short arm of chromosome 8 simplified with color coding: (blue) REPD; (green) REPP; (yellow) the region between these repeats; (red) the region between REPD and the telomere. (a) The common inversion of 8p23.1. (b) deletion of the interval between the repeats with a residue of both repeats remaining (small light blue and green arrows). (c) Duplication of the interval between the repeats with three copies of REPP mixed with REPD repeats at two of the three repeat loci. (d) Copy number variation in which multiple copies of the DEFB4 repeat (light blue) can mimic the appearance of a duplication (c). (e,f) Classical inverted duplicated and deleted chromosome 8s with a proximal duplication breakpoint in the 8 centromere (e) or in band 8p21.2 (f). (Dark blue) The duplicated regions (with an arrow to indicate their orientation); (red) the deleted region. (g) The supernumerary neocentric marker chromosome 8 with the duplicated regions (red, with an arrow to indicate their orientation) flanking the region between the repeats (small light blue and green arrows). (h) The duplicated and triplicated chromosome 8: (yellow) the duplicated region; (red) the triplicated region; (red arrows) the approximate position of the MYOM2 repeats. (i) The unbalanced der(4)(t(4;8)(p16.1p23.1) translocation derived from mothers who are doubly heterozygous for the common inversions of chromosome 4 (left pair) and chromosome 8 (middle pair) producing an unbalanced der(4) chromosome with deletion of the distal (white) segment of 4p and duplication of the distal (red) section of 8p with a residue of REPD(8) (light blue) and REPP(4) (pink) repeats. (j) Terminal deletion of 8p resulting from post-zygotic breakage of a dicentric intermediate with the diagonal line indicating the distinct cell lines with the terminally deleted 8p (left side) and a classic inv dup del(8) chromosome (right side).
