Abstract
Fluorescence of H3-p histone and DAPI was studied at different stages of interphase and mitosis in cells of imaginal disks of third-instar Drosophila melanogaster larvae. Three stages differing in the spatial organization of the chromosome set in mitosis were revealed. At the first stage (prophase, prometaphase), the histone 3 phosphorylation level rises, and the volume occupied by the chromosome set in the nucleus increases. The distinctive features of the second stage (metaphase) are a gradual decrease in the histone 3 phosphorylation (the density ofphosphorylation remaining constant) and a reduction of the volume occupied by the chromosome set. At the third stage (anaphase, telophase), the intensity and density of the signal from H3-p histone decrease, and the volume occupied by the chromosome set reduces. At this stage, in Mer4 larvae, in contrast to the control strain, the cells prematurely pass from anaphase into telophase. In addition, a subpopulation of cells with an abnormally large volume of nuclear DNA during the G1 period was revealed in Mer4 larvae. The cells of this subpopulation do not enter into the DNA synthesis and quit the cycle.
