Understanding the Different Stages of Mitosis

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Prophase:
During prophase, the replicated chromosomes undergo extensive condensation (i.e., coiling). The chromosomes are greatly thickened and shortened but are still contained within the nuclear envelope. Late in prophase, within about 6 min of nuclear envelope breakdown, the mitotic spindle begins to grow, and two triangular 'clear zones' become visible, with one on each side of the nucleus. In three dimensions, the clear zones are actually conical and the nucleus is spherical. With continued spindle expansion, the nucleus rapidly becomes compressed and appears elliptical in the optical section provided by differential interference contrast optics. Prophase ends with the sudden dispersion of the nuclear envelope (nuclear envelope breakdown), and the ...