Overlap between different ANCOR sets. The quantitative relations are illustrative. The highlighted square zooms in on rare ANCORs, which are predicted to be functional. Ro, top 5% of conserved elements in a human-rodent comparison; Ch, the approximately 2.5% of the human genome that can be reliably aligned with chicken ; Func, the 5% portion of the human genome estimated to be functional on the basis of rodent comparisons [10, 15]. Paralogs, noncoding sequences which belong to paralogous families within human genome ; Fi, elements conserved in the pufferfish Fugu rubripes genome ; RoU, ultraconserved elements, defined as > 200 bp of 100% identity between human, mouse and rat ; ChU, the same definition for ultraconserved elements applied to human-chicken comparison .