Chromosome mal-orientation and reorientation during mitosis.
We argue that mal-orientation of mitotic chromosomes is not as rare as once believed. However, unlike bivalents during meiosis I, the reorientation of a mal-oriented mitotic chromosome has yet to be observed. This appears to be due, in part, to the difficulty in differentiating mal-oriented chromosomes from mono-oriented ones which are common during spindle formation in living mitotic cells. We assume that mitotic cells possess mechanisms for correcting chromosome mal-orientations that are similar to those operating during meiosis. However, unlike meiosis, where reorientation appears to be triggered when tension on a K-fiber is relieved or reduced, other factors related to the close proximity of sister kinetochores may also induce reorientation in mal-oriented mitotic chromosomes. We favor a model in which the reorientation of a mitotic kinetochore depends on, and is initiated by, the kinetochore capturing MTs from the pole to which it is reorienting.
Ault
J G
JG
Wadsworth Center for Labs and Research, Albany, New York 12201-0509.
Rieder
C L
CL
D000818:Animals; D002875:Chromosomes; D008870:Microtubules / Q000502:physiology; D008938:Mitosis; D008941:Spindle Apparatus / Q000502:physiology