What changes occur in the nucleus and cell during prophase in mitosis?
* Chromatin fibers become coiled into chromosomes with each chromosome having two chromatids joined at a centromere. * The mitotic spindle, composed of microtubules and proteins, forms in the cytoplasm. * In animal cells, the mitotic spindle initially appears as structures called asters which surround each centriole pair. * The two pair of centrioles (formed from the replication of one pair in Interphase) move away from one another toward opposite ends of the cell due to the lengthening of the microtubules that form between them. In late prophase: * The nuclear envelope breaks up. * Polar fibers, which are microtubules that make up the spindle fibers, reach from each cell pole to the cell’s equator. * Kinetochores, which are specialized regions in the centromeres of chromosomes, attach to a type of microtubule called kinetochore fibers. * The kinetochore fibers “interact” with the spindle polar fibers connecting the kinetochores to the polar fibers. * The chromosomes begin to migrate t
