The stage of mitosis or meiosis in which the nuclear membrane disintegrates and the centrioles reach the poles of the cell, while the chromosomes continue to contract.
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pro·meta·phase -'met-ə-.fāz n a stage sometimes distinguished between the prophase and metaphase of mitosis or meiosis and characterized by disappearance of the nuclear membrane and formation of the spindle
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pro·meta·phase (pro-metґə-fās) the phase of cell division that follows prophase; it begins with the disintegration of the nuclear membrane, after which microtubules from each pole of the spindle bind to the kinetochores of the chromosomes, which begin moving toward the cell equator.Medical dictionary. 2011.