It has been postulated that illegitimate function of the recombination-activating gene (RAG) complex, whose normal physiological activity mediates V(D)J recombination, may be behind the deletions in the CDKN2A/B gene cluster and the many other recurrent ALL deletions, for example, IKZF1 (IKAROS), a key transcription factor that regulates the commitment of hematopoietic precursors in B cells [11]. Here, IKZF1 is linked to acute lymphoblastic leukemia.