[Activity of the nucleolus-organizing regions of the chromosomes of normal and transformed spleen cells in the African green monkey].

The activity of nucleolus organizer regions (NOR's) of chromosomes in the African green monkey cells has been studied before and after the transformation. In cells before their transformation, one or two chromosomes entering into association and possessing NORs are involved in the formation of one nucleolus. In transformed cells no correlation between the numbers of nucleoli in interphase and those of chromosomes possessing NORs was revealed in metaphase plates. It is supposed that in chromosomes of the transformed cells with faintly stained NORs the gene activity is preserved only in part.