Many sub-types of T-cell leukemias are associated with chromosomal translocations involving the T-cell receptor genes (TCRA, TCRB, TCRD and TCRG). Because of the somatic rearrangement of the TCR genes that occurs normally, these genes can accidentally associate with a proto- oncogene in a chromosomal translocation, thus activating it, resulting in a T-cell neoplasia. Below is a table of genes involved in these translocations. This disease specific set contains CCAP BACs that span the known breakpoint regions in order to detect disruption of the normal sequence using FISH.