Cell cycle - The mitotic spindle: A self-made machine

The mitotic spindle is a highly dynamic molecular machine composed of tubul in, motors, and other molecules. It assembles around the chromosomes and di stributes the duplicated genome to the daughter cells during mitosis. The b iochemical and physical principles that govern the assembly of this machine are still unclear. However, accumulated discoveries indicate that chromoso mes play a key role. Apparently, they generate a local cytoplasmic state th at supports the nucleation and growth of microtubules. Then soluble and chr omosome-associated molecular motors sort them into a bipolar array. The eme rging picture is that spindle assembly is governed by a combination of modu lar principles and that their relative contribution may vary in different c ell types and in various organisms.