(A) The probes used for the FISH studies, ordered on the 5q31q35 and 12p12p13 regions of normal chromosomes 5 and 12. (B) Probes detected on each derivative chromosome of a t(5; 12)(q31q33; p12) in pre-B ALL. The probes derived from chromosome 12 are shown in bold. Note a deletion of 5q32 region flanked by y773D3 and y756A2, as well as a loss of 12p12 sequences between c12pC6 and c106B9.