Chromosome number of in vivo and in vitro cultured Krebes-2 carcinoma of mice: the selective property of the in vitro culture medium.

The chromosome number of the Krebs-3 ascites carcinoma maintained in Swiss mice was found to be grouped about a modal number of 78-79. After in vitro culture in medium No. 858 (modified) containing 10 per cent calf serum, primary cultures showed a shift to a smaller number of chromosomes. This medium when used for originating single-cell cultures favored the selection of cells with a modal chromosome number of 64-65. The cell lines selected by the medium were, for the most part, stable with respect to maintaining the same modal number both in vitro and in vivo.