The radial positions of metaphase chromosomes may be a consequence of the relative strength of their interaction with the spindle and their size.
Microtubule oriented forces acting on chromosomes on spindles in mitosis and meiosis will produce a radial component of force in the plane of the metaphase plate. The strength of this vector will depend on the angle at which the microtubule meets the plate. Radial forces will tend to segregate chromosomes to peripheral or central positions, depending on their size, and also on the strength of the activity of individual centromeres. In prometaphase, forces pushing chromosomes from the poles will tend to force them to the periphery of the metaphase plate, as seen in radial metaphases. Tension towards the poles at late metaphase will pull smaller chromosomes and those with more powerfully active kinetochores towards the centre of the plate. If the two genomes in a hybrid cell have different centromeric activities, their chromosomes will be segregated. Microtubule assembly and disassembly, and motor proteins such as the kinesins and dynein which haul organelles along microtubules, can provide forces in both directions.
Fletcher
H L
HL
School of Biology and Biochemistry, Queens University of Belfast, Medical Biology Centre, UK.
D001696:Biomechanical Phenomena; D002875:Chromosomes / Q000378:metabolism / Q000648:ultrastructure; D006822:Hybrid Cells / Q000502:physiology / Q000648:ultrastructure; D008677:Metaphase; D008954:Models, Biological; D009068:Movement; D008941:Spindle Apparatus / Q000378:metabolism / Q000648:ultrastructure; D013314:Stress, Mechanical