Mitotic Behavior of Induced Chromosomal Fragments Lacking Spindle Attachments in the Neuroblasts of the Grasshopper

Abstract

X-ray-induced chromosomal fragments in dividing neuroblasts of Chortophaga viridijasciata, although lacking spindle attachments, show similar behavior and distribution to the chromosomes, indicating that polar repulsions effect the equatorial position at metaphase; that the separation of the chromatids is autonomous; that the orientation and migration toward the poles is due either to protoplasmic currents or to an expanding "Stemmkorper" (Bl[image]r); and that the kinetochore functions mainly in making the orientation and separation of the chromosomes uniform and equal. Evidence for delayed attachment of fragments to broken chromosome ends is presented and suggested as an explanation of "delayed fragmentation.".