Fusion genes are formed when two different genes combine to create a new gene. This process can occur due to various reasons, such as chromosomal rearrangements or genetic mutations. Fusion genes can lead to the production of abnormal proteins that may disrupt normal cellular functions. These genes are often associated with certain types of cancers, such as chronic myeloid leukemia and lung cancer. The presence of fusion genes can serve as important biomarkers for diagnosis and treatment, as they may indicate specific therapeutic targets or help predict patient outcomes.