C-banding studies in patients with Ph1+ chronic granulocytic leukaemia.

The bone marrow chromosomes of 15 patients with Ph1+ chronic granulocytic leukaemia were studied, using both G- and C-banding. In all cases the Ph1 chromosome was formed by the translocation between chromosomes 9 and 22 and the material from chromosome 22 was found to be translocated randomly onto one or other of the pair of 9 chromosomes. Preliminary results suggest that when the translocation was on the 9 chromosome having a smaller C-band, additional abnormalities occurred in blastic transformation, whereas when the 9 chromosome with the larger C-band was involved in the translocation, additional abnormalities were not found in blastic transformation. These observations require confirmation from a larger series. C-banding also showed that there was a greatly increased heteromorphism of the C-band areas of the chromosome pair 9 in this disease, and an increased heteromorphism in the C-bands of chromosome pair 1, when compared with a control group.