The chromocenter integrates the entire Drosophila genome into a unit. The formation and reorganization of chromocenter are genetically determined. Currently, several mutations affecting the structure of chromocenter have been described. In this work, I present evidence on the time of the formation and reorganization of chromocenter in mitotic and meiotic cells of females of the wild type and the ff16 mutant line obtained by selection of mosaic clones produced from mitotic recombination of chromosomes in the dividing embryo cells. In females homozygous for this mutation, the second stage of the formation of chromocenter (joining two groups of nonhomologous chromosomes X-4 and 2-4 into a united ring structure -X-2-3-4-) is disturbed. The differences between the mitotic and meiotic reorganization of chromocenter and the role of chromocenter in the control of chromosome segregation are discussed.