1983 年 58 巻 1 号 p. 1-9
Karyotypes of a mammary cancer spontaneously developed in the domestic cat were analysed in comparison with those of normal somatic cells (2n=38). This tumor was characterized by having bimodal distribution of chromosome numbers: one at hypodiploid and another at hypotetraploid ranges. Based on comparison of karyotypes between the hypodiploid and hypotetraploid cells, the former was suggested to be developed primarily and the latter by duplication of the hypodiploid karyotype. Malignant transformation of this tumor was assumed to be due to the occurrence of monosomics in some chromosome pairs. Although only 2 per cents of the tumor cells were eudiploid so far they were maintained in in vitro culture, the cell population changed markedly to an eudiploid mode (88%) after storage in deep freezing (-80°C). This phenomenon was explained due to the fact that the diploid cells had a more resistance to the hostile condition than the other cells with altered karyotypes.
