FISH analysis of MM patients using the IGHconstant regions (green) and the YAC 764-H1 (red) as probes. (A) and (B) Interphase and metaphase nuclei of patient no. 30. The colocalized signals at der(14q) are indicated. YAC 764-H1 recognized two chromosomes 4 on metaphase spreads indicated by X. In one chromosome 4, the signal is faint and consistent with a der(4) chromosome (see text). (C) and (D) Interphase nuclei from cases 9 and 24, respectively. (E) and (F) Interphase and metaphase nuclei of patient no. 18. In this case, the IGH probe is colocalized with YAC 764-H1 on the tip of one chromosome 4p (F); the other chromosome 14q32 is apparently absent, but the second chromosome 4 can be seen (indicated by X).