Stages of Mitosis - Prophase, Prometaphase, Metaphase, Anaphase & Telophase




In mitosis, the nucleus divides to produce two nuclei that are genetically identical to each other and to the parent nucleus. To prepare for division, the DNA replicates in the preceding interphase. Although the chromosomes are not yet compacted and visible as discrete bodies, we illustrate them as such to show the formation of a second chromatid per chromosome. Also during interphase, the cell replicates its centrosome. Centrosomes are microtubule organizing centers, which are important for chromosome movement during mitosis. In many organisms, each centrosome contains a pair of centrioles. In the first phase of mitosis, called prophase, chromatin coils and condenses, resulting in compacted chromosomes that are visible with a light microscope. In prometaphase, the nuclear envelope breaks down and microtubules emanating from the centrosomes attach to the chromosomes. The microtubules attach to structures called kinetochores, which are found in the centromeres of the chromosomes. In metaphase, the centromere regions connecting paired chromatids become aligned in a plane at the cell's equator. In anaphase, the centromere pairs from each chromosome separate, and the single chromatids—which are now considered individual chromosomes—move toward the poles. In telophase, the separating chromosomes reach the poles. The division of the cytoplasm, called cytokinesis, also begins during this phase. As the cells enter the next interphase, the nuclear envelopes and nucleoli re-form and the chromatin again becomes diffuse.



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