Some characteristics of karyotype changes in the NK/Ly ascites tumor during its growth.

The NK/Ly ascites tumor has been studied with respect to the karyotype and its changes during tumor growth. The numeric stem line of the tumor cells is 43. The chromosome markers are as follows: a large metacentric chromosome, a large submetacentric chromosome with the long arm divided or, in a few cases, not divided by achromatic space, a large telocentric chromosome with a well-visible achromatic space which divides its long arm into two sections, and 1--2 extremely small chromosomes. The combination of the large metacentric chromosome, the large submetacentric chromosome with achromatic space, and of 1--2 extremely small chromosomes is modal. With the NK/Ly tumor growth, the number of modal cells decreases, while the variability in the number of chromosomes in the cells increases, i.e. their number is diminishing, and so is the percentage of cells with the modal combination of chromosome markers. On the 12th day of tumor growth, no clearly visible stem line can be noticed. The observed karyotype changes may be considered, alongside with other causes, to be due to longer period of the cell cycle during the NK/Ly ascites tumor growth.