Pattern of the unidentified exons. The closed boxes represent exons in the genomes. Unidentified exons in macaques are presented as blue boxes. Intergenic regions and introns are depicted by thick and thin horizontal lines, respectively. (A) extended exons. (B) novel exons. These exons were further classified into internal (right panel) and external (left panel) exons. The number of genes in each category is shown on the left of each schema. The number of unidentified exons that have not been found even in the EST sequences is shown in parentheses.