Figure 1.

A genome-wide view of human Alu activity. A total of 850,044 full-length (>268 bp) genomic Alus were identified in hg18 of the reference human genome sequence and assigned to known Alu subfamilies. Alu elements frequently have sequence changes relative to consensus sequences. The number of changes for each full-length copy is indicated on the x-axis; the copy number for a given level of sequence variation is indicated on the left y-axis. Pink data points mark the mobilization activities of the 89 Alu copies that were examined in this study (labeled on the right y-axis). In sum, 8 AluJ, 27 AluS, and 54 AluY copies were tested, spanning a range of subfamilies and variation levels. Note that elements with fewer changes relative to consensus sequences (zero changes) generally had the highest levels of activity; no elements below 10% variation (28 changes) were active. Please see Supplemental Table 1 for additional details and error measurements.