In human neuroblastomas, gain of an entire chromosome 7 occurs in 40% of tumors and appears to be prevalent in all tumor stages, whereas gain of 7q, observed in 12% of human tumors, is more common in higher stage tumors.9 Three tumors harbored a gain of the entire mouse chromosome 12, which is syntenic to human chromosome 2p and includes the MYCN locus, as well as human chromosome 14q and parts of human chromosome 7p and 7q (Figure 4a and Supplementary Figure 4d). The gene discussed is MYCN; the disease is neuroblastoma.