ANAPHASE AND CYTOKINESIS IN THE ABSENCE OF CHROMOSOMES

ANAPHASE and cytokinesis are key processes in the segregation of repli cated chromosomes to the daughter cell: in anaphase, chromosomes move apart; in cytokinesis, a cleavage furrow forms midway between the sepa rate chromosomes. Some evidence suggests that chromosomes may be invol ved both in controlling the timing of anaphase onset(1-3) and in dicta ting the position of the cleavage furrow(3). Other evidence indicates that the controlling mechanisms are intrinsic to the spindle and the c ell(4-7). Here we test these possibilities in grasshopper spermatocyte s by observing spindles and cells after removal of chromosomes. We fou nd that both anaphase and cytokinesis occur independently of chromosom es: stage-specific changes occur at an appropriate time and in the cor rect way, despite the absence of chromosomes. This finding is particul arly noteworthy because chromosomes have an important impact on spindl e microtubule assembly(8,9) and the timing of anaphase onset(10) in th ese cells.