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QuestionAnatomy and Physiology

Phases of Mitosis Mitosis is divided into five main phases: prophase, prometaphase, metaphase, anaphase, and telophase. Each phase has distinct characteristics that contribute to the proper separation and distribution of replicated genetic material. II. Duplication of DNA The duplication of DNA occurs during the S phase of the cell cycle, which precedes mitosis. This ensures that each new cell will have an exact replica of the genetic material. III. Chromatin and Chromosomes Chromatin refers to the loosely coiled DNA and associated proteins found in the nucleus of interphase cells. When a cell enters mitosis, chromatin condenses into chromosomes, which are more densely packed and visible structures. Chromosomes consist of two sister chromatids joined at the centromere. IV. Pulling Apart of Chromatids Chromatids are pulled apart during anaphase. The sister chromatids separate at the centromere, and each moves toward opposite poles of the cell, ensuring that each new nucleus will receive one copy of each chromosome. V. Role of Centrioles Centrioles are responsible for organizing the mitotic spindle, a structure composed of microtubules that facilitates the movement of chromosomes during mitosis. The centrioles duplicate during the S phase of the cell cycle and migrate to opposite poles of the cell during prophase. VI. Development of a New Nuclear Membrane A new nuclear membrane develops during telophase, the final phase of mitosis. The nuclear membrane reforms around each set of chromosomes, creating two separate nuclei, each containing the complete genetic material. VII. Single Line of Chromosomes A cell with a single line of chromosomes is in metaphase. During this phase, chromosomes align at the metaphase plate, an imaginary line equidistant from the two spindle poles. VIII. Phases with No Longer Visible Individual Chromosomes Individual chromosomes are no longer visible during prophase, prometaphase, and telophase. In prophase, chromosomes condense and become visible, but the nuclear membrane is still present, obscuring individual chromosomes. In prometaphase, the nuclear membrane breaks down, allowing the spindle fibers to attach to the chromosomes, but the individual chromosomes are not distinguishable. In telophase, the nuclear membrane reforms around each set of chromosomes, and the chromosomes begin to decondense, making them less visible.