ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Mutations in the Abl1 gene are commonly associated with chronic myelogenous leukemia (CML) where the Abl1 gene is activated by being translocated within the Bcr (breakpoint cluster region) gene on chromosome 22, creating a new fusion gene, Bcr-Abl, that encodes an unregulated, tyrosine kinase.