Experimental validation of gibbon–human chromosomal rearrangements. (a) Examples of interchromosomal rearrangement. Two gibbon clones, BACs CH271–279L5 (left) and CH271–301L21 (right), whose end sequences aligned to different human chromosomes, are hybridized to human and gibbon metaphases (NLE metaphase in the upper right-hand corner). The FISH assays show split signals in human and a single signal in gibbon, confirming that the two BACs span the 5b/16a and 5c2/16b1 breakpoints, respectively. (b) Two examples of intrachromosomal rearrangements. Gibbon BACs CH271–203C4 (left) and CH271–131G15 (right) span the 14a1/14a2 and 9b1/9b4 junctions, respectively, yielding split signals in human metaphases, but single signals in gibbon. (c) Cohybridization FISH experiments of gibbon BACs CH271–346A15 (red) and CH271–131D24 (green) against gibbon (left) and humans (right) metaphases. The two BACs span the junctions 6c/2d and 6d/2e, respectively. In humans, the two BACs span the breakpoint region in gibbon, as shown by the yellow color representing the fusion of red and green signals. (d) A reciprocal assay wherein human BACs spanning the 6c/6d and 2d/2e breakpoints (RP11–1007C6 and RP11–11N16, respectively) were hybridized on human (right) and gibbon (left) metaphases. In gibbon, these BACs span the regions that face each other on NLE chromosomes 17 and 22b, and therefore produce a yellow signal. (SB) Synteny break.
