Using green fluorescent protein probes and rapid acquisition of high-resolu
tion fluorescence images, sister centromeres in budding yeast are found to
be separated and oscillate between spindle poles before anaphase B spindle
elongation. The rates of movement during these oscillations are similar to
those of microtubule plus end dynamics. The degree of preanaphase separatio
n varies widely, with infrequent centromere reassociations observed before
anaphase. Centromeres are in a metaphase-like conformation, whereas chromos
ome arms are neither aligned nor separated before anaphase, Upon spindle el
ongation, centromere to pole movement (anaphase A) was synchronous for all
centromeres and occurred coincident with or immediately after spindle pole
separation (anaphase B). Chromatin proximal to the centromere is stretched
poleward before and during anaphase onset. The stretched chromatin was obse
rved to segregate to the spindle pole bodies at rates greater than centrome
re to pole movement, indicative of rapid elastic recoil between the chromos
ome arm and the centromere. These results indicate that the elastic propert
ies of DNA play an as of yet undiscovered role in the poleward movement of
chromosome arms.