Anaphase transport of akinetochoric fragments in tipulid spermatocytes. Electron microscopic observations on fragment-spindle interactions.

Akinetochoric chromosomal fragments in spermatocytes of mutant Pales ferruginae are transported polewards in anaphase. During migration their surfaces form radial lamellar projections between which non-kinetochoric spindle microtubules become arranged in an orderly fashion. The same morphological features had been observed earlier in intact chromosomes in late anaphase. It is assumed that the fragments are transported by some kind of poleward directed "streaming" force of the anaphase spindle, which is applied to the fragment's surface. Non-kinetochoric microtubules are thought to be engaged in the generation or, at least, in the transmission of this spindle force. Due to the morphological similarities with akinetochoric fragments, extra-kinetochoral application sites for anaphase spindle forces can be also suggested for chromosomes possessing kinetochores.