Pac-Man does not resolve the enduring problem of anaphase chromosome movement.
The Pac-Man hypothesis suggests that poleward movement of chromosomes during anaphase A is brought about by: disassembly of kinetochore microtubules (MTs) at the kinetochore; generation of the poleward force exclusively at or very close to the kinetochore; and the required energy coming from coupled disassembly of these MTs. This model has become widely accepted and cited as the sole or major mechanism of anaphase A. Rarely acknowledged are several significant phenomena that refute some or all of these postulates. We summarise these anomalies as follows: poleward movement of chromosomes occurring without insertion of any MTs at the kinetochore; "anaphase" shortening of kinetochore fibres in spindles entirely devoid of chromosomes and, presumably, kinetochores; continued movement of chromosomes while their severed kinetochore stub elongated poleward after treatment with UV microbeams; and fluxing of tubulin subunits through kinetochore MTs during anaphase A, indicating that during anaphase, kinetochore MTs disassemble partly or solely at the poles.
Pickett-Heaps
J D
JD
School of Botany, University of Melbourne, Parkville, Victoria, 3052, Australia.
Forer
A
A
D000705:Anaphase / Q000502:physiology*; D002875:Chromosomes / Q000502:physiology*; D018386:Kinetochores / Q000502:physiology; D008870:Microtubules / Q000502:physiology; D008954:Models, Biological; D009068:Movement