In prophase, which is the first stage of mitosis, several key events take place:
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Chromosome condensation: The parent cells chromosomes, which were duplicated during the S phase, condense and become highly compact. Each chromosome consists of two identical sister chromatids joined at a point called the centromere, and these structures appear as X-shaped bodies when viewed under a microscope.
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Mitotic spindle formation: The mitotic spindle begins to develop during prophase. As the cells two centrosomes move toward opposite poles, microtubules gradually assemble between them, forming the network that will later pull the duplicated chromosomes apart.
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Nuclear envelope breakdown: In late prophase, the nuclear envelope breaks down, releasing the condensed chromosomes and allowing the mitotic spindle to capture and organize the chromosomes.
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Nucleolus disappearance: The nucleolus, a part of the nucleus where ribosomes are made, disappears during early prophase, indicating that the nucleus is getting ready to break down.
These events set the stage for the subsequent stages of mitosis, including prometaphase, metaphase, anaphase, and telophase.
In summary, prophase is a crucial stage in mitosis where the cell prepares for chromosome segregation and division by condensing its chromosomes, forming the mitotic spindle, and breaking down the nuclear envelope.
