Figure 3. Alu quiescence in the orang-utan lineage.
We identified only ∼250 lineage-specific Alu retroposition events in the orang-utan genome, a dramatically lower number than that of other sequenced primates, including humans. The total number of lineage-specific L1, SVA and Alu insertions is shown (pie chart) at the terminus of each branch of the phylogeny of sequenced great apes shown in grey at left, along with the rate of insertion events per element type (bar graph). Reduced Alu retroposition potentially limited the effect of a wide variety of repeat-driven mutational mechanisms in the orang-utan lineage that played a major role in restructuring other primate genomes.