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Which of the following does NOT happen during mitosis?

A. Synthesis of DNA.
B. Condensing of chromosomes.
C. Formation of the spindle.
D. Separation of sister chromatids at the centromeres.

1 Answer

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Final answer:

DNA synthesis does not occur during mitosis; it happens during the S phase of interphase. Mitosis involves chromosome condensation, nuclear envelope breakdown, spindle formation, and sister chromatid separation.

Step-by-step explanation:

The process that does NOT happen during mitosis is the synthesis of DNA. Mitosis is a phase in the cell cycle where a eukaryotic cell divides to produce two identical daughter cells with the same number of chromosomes as the parent cell. However, DNA replication occurs during the S phase of interphase, not within the stages of mitosis itself. During mitosis, the following events occur: chromosomes condense, the nuclear envelope breaks down, the spindle apparatus forms, and sister chromatids are separated into daughter cells.

More specifically, the stages of mitosis in order include:

  • Prophase: Chromosomes condense and become visible, the nuclear envelope begins to disintegrate, and the mitotic spindle begins to form.
  • Prometaphase: The nuclear envelope completely breaks down and the spindle microtubules attach to kinetochores of chromosomes.
  • Metaphase: Sister chromatids align at the metaphase plate in the center of the cell.
  • Anaphase: The cohesin proteins are cleaved, and sister chromatids are pulled toward opposite poles as the spindle fibers shorten.
  • Telophase: Nuclear envelopes re-form around the separated sister chromatids, now considered individual chromosomes, and the chromosomes begin to decondense.
  • Cytokinesis (often associated with telophase): This is when the division of the cytoplasm occurs, resulting in two daughter cells.
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