Figure 3. Evidence for exchange of SST1 on NOR-bearing chromosomes in chimpanzee and bonobo genomes.

A) Ideograms of all the NOR-bearing chromosomes in human, chimpanzee, and bonobo, annotated with the human numbering system. The directionality of 45S rRNA gene arrays (grey) and SST1 arrays (colored 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 subfamily indicated. Random regions of the genome (randBins, randGC which was GC matched) were used to determine background. C) All SST1 monomers from the chimpanzee genome were subjected to phylogenetic analysis using the maximum likelihood method. The color indicates the source chromosome. Notably, the SST1 monomers from chromosomes 13, 14, 18, 21, and 22 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. Notably, the SST1 monomers from chromosomes 14 and 22 form a single branch, indicating a high degree of similarity. E) SST1 monomers from human, chimpanzee and bonobo were subjected to phylogenetic analysis using the maximum likelihood method. The three subfamilies are apparent.