Explain the four stages of mitosis ( 8 marks).

DNA is replicated in interphase. 1) Prophase is first stage. Nuclear envelope breaks down and chromosomes condense and free in cytoplasm. Centrioles move to opposite ends of cell to form network of fibres across cell called spindle.2) Metaphase= chromosomes line up in middle of cell, attach to spindle at their centromere. 3)Anaphase= centromeres divide separating the 2 sister chromatids of chromosome. Spindles contract pulling chromatids to opposite ends of cell. 4) Telophase= chromatids uncoil (called chromosomes again), nuclear envelope forms around each group of chromosomes (2 nuclei) and cytoplasm divides. Now two daughter cells genetically identical.

BM

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