Conserved syntenies and an evolutionary model for LG3 and LG12. (A) LG3 and LG12 share conserved syntenies with Hsa16p and Hsa22 and other mammalian chromosomes in addition to Hsa17. (B) A model for the origin of Hsa17, Hsa16p, Hsa7b, and Hsa22. The overlapping conserved syntenies of orthologs of these human chromosome segments in fish, mouse, cat, and human suggest that they were originally part of a single chromosome that fragmented in the tetrapod lineage. Hsa10q and Hsa19p may have joined LG12 and LG3, respectively, after the ray-fin genome-wide duplication. Accession nos. are listed in Supplementary Data at http://www.genome.org.