In order to further identify somatically acquired 2nd hits leading to leukemia development in both Pax5-het/Aid-het and Pax5-het/Aid-KO B-ALLs, we performed whole-exome sequencing of five Pax5-het/Aid-het tumors, eight Pax5-het/Aid-KO tumors, and paired samples of germline tail DNA as a reference. The gene discussed is PAX5; the disease is leukemia.