Diagram of Hsa21 and the regions of trisomy in the various mouse models of DS. Human chromosome 21 and specific genes that may contribute to the development of leukemia in children with DS are shown on the left. Syntenic regions on Mmu16, and the mouse models in which they exist in 3 copies, are depicted on the right. Note that the Tc1 mouse is trisomic for the majority of human chromosome 21. Mouse models outlined in red are discussed under “Utility of animal models of DS.”