BCR and leukemia: This reciprocal chromosomal translocation event, which is generated by t(9,22) (q34;q11), also contributes to between 20 and 30% of adult B cell acute lymphoid leukemia (B-ALL).1BCR-ABL encodes the BCR-ABL oncoprotein which has sustained kinase activity, and is the central factor in initiating Ph+ leukemias and driving their progression.