Research the Literature on your Own What controls spindle
microtubule polymerization? (Hints: check the literature on
centrosomes with special attention to an isoform of tubulin
called “gamma-tubulin”. Look into the idea that chromosomes too
are able to increase the probability of microtubule
polymerization by looking up “ran-GTP” and its ability to alter
the tubulin-microtubule equilibrium. Look also at recent
evidence for kinetochore-mediated initiation of microtubule
growth.) When all these facts are in hand, consider the
implications of your knowledge for a basic understanding of how
the spindle forms. Is the diversity you have now seen the source
of fundamental variation in spindle function, or is it just
another example of biological diversity on a fundamental
process? How are sister chromatids held together, and how is
this connection severed to allow anaphase onset? (Hints: check
out the literature on cohesin, but be sure to get more than one
point of view, e.g., work from both the Nasmyth and the Kos