Array-CGH copy number analyses of these malignancies identified amplification of chromosome 15 (and consequently Myc) and focal deletions of the second allele of Pax5. Exome sequencing revealed B ALL samples from ENU treated mice had 5-fold more exonic mutations than MuLV infected mice and identified recurrent mutations in the human ALL mutated genes: Pax5, Jak3, Ptpn11, Jak1, and Nras. Pax5 mutations were almost exclusively within the DNA-binding paired domain and equivalent to mutations observed in human B ALL. This evidence concerns the gene PAX5 and acute lymphoblastic leukemia.