Fig. 2. Schematic illustration of the generation of microtubule asymmetry in grasshopper spermatocytes. (A) Bipolar spindles with an asymmetric microtubule distribution were produced by removing all chromosomes, except the X, in prometaphase of meiosis I cells (a,b). The X chromosome subsequently causes spindle asymmetry by promoting microtubule assembly at its proximal pole (c). (B) Greater microtubule asymmetry was produced by further removal of the aster from the achromosomal spindle pole (a,b) following extraction of all but the X chromosome, yielding a cell with a monopolar spindle bearing only the X chromosome (c). (C) The greatest spindle asymmetry was created by cutting cells between segregating chromosomes in anaphase (a,b), producing two cells, each containing a half-spindle with all segregated chromosomes (c).