Muscle and nerve cells will remain in Go until they die. Liver cells may be recruited back to the cell cycle under certain cues, such as growth factors. Duplicated chromosomes that cannot be distinguished individually due to loosely packed chromatin fibers. Chromatin fibers condense into discrete, observable chromosomes, composed of two identical sister chromatids joined at the centromere . It is composed of microtubules between the two centrosomes or microtubule organizing centers.
Centrosomes move apart.
Nuclear envelope fragments, which allows microtubules to interact with the highly condensed chromosomes. Each chromatid now has a specialized structure, the kinetochore, located at the centromere region. Kinetochore microtubules become attached to the kinetochores and put the chromosomes into agitated motion . Centrosomes are positioned at opposite poles of the cell. Chromosomes move to the metaphase plate, the plane equidistant between the spindle .