Surprisingly, under this scenario, B-ALL development was observed in 30.4% (7 out of 23) of Pax5-het/Aid-het and in 30% (9 out of 30) of Pax5-het/Aid-KO animals, respectively (Fig. 1b), closely resembling the penetrance of B-ALL development in both the Pax5-het group4 and the carriers with the heterozygous PAX5 c.547G>A mutation7. This evidence concerns the gene PAX5 and acute lymphoblastic leukemia.