Chronic myeloid leukaemia (CML), a myeloproliferative disorder, is caused by a chromosomal translocation that results in a fusion of two genes, the breakpoint cluster region protein (BCR) gene on chromosome 22 and the Abelson murine leukaemia viral oncogene homolog 1 (ABL1) gene on chromosome 9 [1]. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.