Non-random chromosomal changes involving chromosomes 6 and 7 in spontaneous rat immunocytomas

G-banding analysis of seven Ig-secreting spontaneous rat immunocytomas showed a consistent translocation of the distal part of the q-arm of chromosome 7 to the telomeric end of chromosome 6. The breakpoints were assigned to q3.3 on chromosome 7 and q3.2 on chromosome 6. Previously, we found a similar translocation pattern in mouse plasmacytomas induced by different agents. The distal part of the q-arm of chromosome 15 was translocated to the telomeric end of chromosome 12, known to carry Igh, the immunoglobulin heavy chain cluster. The banding homologies between the chromosomes involved in the translocation in the two species suggest that a similar mechanism is responsible for plasmacytomagenesis in both. We also predict that the rat Ig heavy chain gene cluster will be located to the terminal segment of chromosome 6.