Fig. 5. Centromeres on ape sex chromosomes.

a, Left, active alpha satellite suprafamilies (SFs) on the primate phylogenetic tree. Active centromeres in each chromosome have different higher-order repeats in chromosome-specific organization and similar repeats in pan-chromosomal organization. Right, centromeres for each branch (not to scale) with alpha satellite suprachromosomal family composition of the active core indicated in the middle and of the dead flanking layers on the sides. Each branch has one or more alpha satellite suprachromosomal family fewer than in African apes but may also have layers not shared with human (indicated by hues of the same colour). The African ape centromere cores are shown as horizontal bars of SF1–SF3 as each chromosome usually has one alpha satellite suprafamily, which differs with each chromosome. b, The UCSC Genome Browser tracks of alpha satellite suprafamily composition of centromere cores and flanks for cenY and cenX (not to scale). CenX is surrounded by stable vestigial layers (that is, the remnants of ancestral centromeres), whereas cenY has a ‘naked’ centromere devoid of such layers. Thin grey lines under the tracks show overlaps with segmental duplications. In gorilla cenX, SF3 was replaced by SF2 and then by SF1 (see details in Supplementary Note 7).