Fig. 3: Inversions and evolutionary rearrangements in great apes.

a, Alignment plot of gorilla chromosome 18p and HSA16p shows a 4.8 Mb inverted transposition (yellow). SDs are shown with blue rectangles. b, Experimental validation of the gorilla chromosome 18 inverted transposition using FISH with probes pA (CH276-36H14) and pB (CH276-520C10), which overlap in human metaphase chromosomes. The transposition moves the red pB probe further away from the green pA probe in gorillas, resulting in two distinct signals. FISH on metaphase chromosomes using probe pC (RP11-481M14) confirmed the location of a new inversion to the terminal end of the short arm of PAB chromosome 2. Each FISH experiment was repeated three times, and ten metaphase spreads with the corresponding fluorochromes were captured for each experiment. Scale bar, 1 µm. c, An evolutionary model for the generation of the inverted transposition through a series of inversions mediated by SDs. d, Alignment plot of orangutan chromosome 2 homologues to HSA3 highlights a more complex organization than previously known by cytogenetics¹¹⁷: a new inversion of block 5A is mapping at the terminal end of the short arm of chromosome 2 in both PAB and PPY. e, A model of serial inversions requires three inversions and one centromere repositioning event (ENC) to create PPY chromosome 2, and four inversions and one ENC for PAB. Red asterisks show the location of SDs mapping at the seven out of eight inversion breakpoints. ANC, ancestor.