PARTIAL DELETION OF CHROMOSOME 2 IN MYELOCYTIC LEUKEMIAS OF IRRADIATED C3H-HE AND RFM MICE

Chromosomes of mouse myelocytic leukemias that developed in 7 irradiated mice, 3 C3H/He males, 1 RFM female, and 3 RFM males were analyzed with chromosome-banding techniques. Chromosomes #2 were partially deleted in 6 of the 7 mice. Although the deleted #2 chromosomes varied in size in the 6 mice, one common characteristic was noted in all these deletions: A segment lying between a certain band in the region 2C and a band in the region 2E, including the whole region 2D, was missing. Another consistent abnormality was an addition or a loss of the Y-chromosomes in the fraction of cells in all 6 males. In addition to these consistent abnormalities, various chromosomes had structural abnormalities. The RFM female, which did not have the abnormal #2 chromosome, had abnormalities in chromosomes #3, 4, 10, 11, 12, and 15 and in the X-chromosome. Of the 20 chromosome pairs, only such chromosomes as #1, 5, 8, 14, 17 and 19 and the Y-chromosome did not have the structural abnormalities. The possible role of the partial deletion of the #2 chromosome was considered in relation to the development of mouse myeloid leukemias.