Fig. 3: Evidence for exchange of SST1 on rDNA array-bearing chromosomes in chimpanzee and bonobo genomes.

a, Ideograms of all the rDNA array-bearing chromosomes in human, chimpanzee and bonobo, annotated with the human numbering system (indicated by Hsa prefix). The directionality of 45S rRNA gene arrays (grey) and SST1 arrays (coloured bars) are indicated with arrowheads. b, Predicted PRDM9 binding sites were identified in the chimpanzee genome, and the number of sites per kb is plotted for SST1 arrays for the indicated subfamily. Random regions of the genome (randBins and randGC (GC-matched random regions)) were used to determine background. c, All SST1 monomers from the chimpanzee genome were subjected to phylogenetic analysis using the maximum-likelihood method. The colour indicates the source chromosome. The SST1 monomers from Hsa13, Hsa14, Hsa18, Hsa21 and Hsa22 chromosomes form a single branch, indicating a high degree of similarity. d, All SST1 monomers from the bonobo genome were subjected to phylogenetic analysis using the maximum-likelihood method. The SST1 monomers from chromosomes 14 and 22 form a single branch, indicating a high degree of similarity. e, SST1 monomers from human (Hs), chimpanzee (Pt) and bonobo (Pp) were subjected to phylogenetic analysis using the maximum-likelihood method. The three subfamilies are apparent.