Certain types of human cancer are associated with chromosome rearrangements. For example, chronic myelogenous leukemia (CML) is associated with an aberration of chromosome 22. This abnormal chromosme was originally discovered in the city of Philadelphia and thus is called the philadelphia chromosome. Such chromosome is actually the result of a reciprocal translocation between chromosomes 9 and 22. The translocation breakpoint on chromosome 9 is in the C-abl oncogene and the break point on chromosome 22 is in a gene call bcr. Burkitt’s lymphoma is another exampleof white blood cell cancer associated with reciprocal translocations. These translocations invariably involve chromosome and one of three chromosomes (2, 14 and 22). Translocation involving chromosom 8 and 14 are the most common. In these translocations, the c-myc oncogene on chromosome 8 is juxta posed to the genes for the immunoglobulin chains on chromosme 14. This rearrangement results in the overexpression of the c-myc oncogene in cells that produce immunoglobulin heavy chains in B- lymphocytes.