Chromosome ends and the nuclear envelope at premeiotic interphase in the male grasshopper Brachystola magna by 3-D,E.M. reconstruction

During premeiotic interphase in the male grasshopper Brachystola magna the nucleus is divided into two nuclear envelope bound compartments, one containing the X chromosome and one the autosomes. — The autosomal compartment is characterized by an invaginated nuclear envelope with nuclear pores distributed throughout the envelope. In a polarized region of the cell the pericentric heterochromatic chromocenters are associated with the inner membrane of the envelope invaginations. In this species the chromosomes are telocentric (acrocentric?) and the pericentric heterochromatin marks the proximal chromosome ends. It is concluded that the chromosome ends are attached to the nuclear envelope at premeiotic interphase. — Comparisons are made between the present observations on chromosome arrangements and the nuclear envelope at premeiotic interphase to earlier observations at early meiotic prophase in the same species (Church, 1976). It is concluded that a rearrangement of both the proximal chromosome ends and the nuclear envelope occurs as cells enter meiotic prophase.