AP Biology : 5.2 Meiosis and Genetic Diversity- Study Notes

B. Mitosis
➢ Prophase

  •  Disappearance of the nucleolus and nuclear envelope
  •  Chromosomes thicken and become visible
    ■ Now called chromatin
  • Centrioles in microtubules organizing centers (MTOCs) start to move away from each other towards opposite poles of the cell
    ■ Centrioles spin out system of microtubules known as spindle fibers
    ■ Spindle fibers attach to kinetochore located on centromere of each chromatid


  • Chromosomes begin to line up along equatorial metaphase plate
    ■ Moved along by spindle fibers attach to kinetochores on each chromatid


  • Sister chromatids of each chromosome separate at the centromere and migrate to opposite
  •  Pulled apart by shortening microtubules
  •  Non-kinetochore tubules elongate cell

➢ Telophase

  • Nuclear membrane forms around each set of chromosomes
  • Nucleoli reappear
  • Cytokinesis
    ■ Cytoplasm splits in half
    ■ Cell splits along cleavage furrow
    ■ Cell membrane forms along each new cell, split into distinct daughter cells
    ■ In plant cells, a cell plate forms down the middle instead of a cleavage furrow

➢ Interphase

  •  Cells re enter initial phase, and are ready to start the cycle over again
  • Chromosomes become invisible again
    ■ Genetic material goes back to being chromatin

➢ Purpose of mitosis

  • Produce daughter cells that are identical copies of parent cell
  •  Maintain proper number of chromosomes from generation to generation

➢ Occurs in almost every cell except for sex cells
➢ Involved in growth, repair, and asexual reproduction

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