Tc1 mice carrying a human fragment of Chromosome 21 (Hsa21) are viable, fertile, and normal in size. Only the female carriers consistently transmit the mutation to the germline. When maintained on a background other than (C57BL/6 X 129S8/SvEv), germline transmission is completely abolished. These Tc1 mice contain 42Mb of a freely segregating Hsa21 containing 269 genes, including most of the gene orthologs located on mouse Chromosome 10 (Mmu10), Mmu16, and Mmu17, which have been found to contribute to human Down Syndrome (DS). The Tc1 mouse exhibits several characteristics of DS, including alterations in behavior, learning, memory, synaptic plasticity, cerebellar neuronal number, heart development, mandible size, defects in motor coordination, perturbed hematopoiesis, and reduced tumor angiogenesis. These mice may be useful for studying the genes involved in human chromosome aneuploidy and its role in DS.

These Tc1 mice contain 42Mb (approximately 90%) of a freely segregating human fragment of Chromosome 21 Hsa21 containing 269 genes, including most of the gene orthologs located on mouse Chromosome 10 (Mmu10), Mmu16, and Mmu17, which have been found to contribute to human Down Syndrome (DS). These mice may be useful for studying the genes involved in human chromosome aneuploidy and its role in DS.