G- and C-banding patterns in the T2 murine leukemia

The bone marrow cells of BALB/c mice with T2 murine leukemia were analyzed cytogenetically. Of 98 leukemia metaphases, 16.3% were hypodiploid, 4.1% hyperdiploid, and 79.5% diploid. The distribution of G bands in diploid metaphases indicated that almost half of them were pseudodiploid, with chromosome abnormalities such as trisomies, monosomies, nullisomies, unidentified chromosomes, translocations, deletions, or duplications. Since all mouse chromosomes are acrocentric and can be identified only tentatively most of the anomalies detected with G-banding procedures would have passed unnoticed with conventional cytogenetic techniques. The C-banding pattern of leukemia cells did not differ from that of normal controls. However, a considerable number of leukemia cell metaphases had bridges connecting the centromeric C bands of two or more chromosomes. This phenomenon probably indicates an increased stickiness of the heterochromatin, which may produce mitotic nondisjunction and the appearance of monosomies and trisomies.