ALL is characterized by recurring structural chromosomal alterations, including aneuploidy (high-hyperdiploid, chromosomes ≥51; hypodiploid, chromosomes ≤44) and translocations (e.g., t (12;21)/ETV6-RUNX1, t (1;19)/TCF3-PBX1, t (9;22)/BCR-ABL1, and KMT2A (also known as MLL) rearrangement). The gene discussed is KMT2A; the disease is acute lymphoblastic leukemia.