The Philadelphia Chromosome is an abnormal chromosome found in some patients with certain types of leukemia, particularly Chronic Myeloid Leukemia (CML). It results from a genetic mutation where parts of the BCR gene on chromosome 22 and the ABL gene on chromosome 9 swap places, creating a new fusion gene called BCR-ABL. This fusion gene produces a protein that promotes cancer cell growth. The presence of the Philadelphia Chromosome is significant for diagnosis and treatment. It can be detected through genetic testing, and its identification helps guide therapy options, including targeted treatments like imatinib (Gleevec), which specifically inhibit the BCR-ABL protein's activity.