This chromosomal translocation leads to the fusion of the 5′ region of the BCR gene with the sequences upstream of the second exon of the ABL1 gene (almost the entire gene coding for this tyrosine kinase), giving rise to the p190 fusion protein found in approximately 85% of Ph+ paediatric ALL and 50–70% of Ph+ adult ALL [203, 204]. This evidence concerns the gene ABL1 and acute lymphoblastic leukemia.