Mitosis and cytokinesis


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Mitosis and cytokinesis

  1. 1. Mitosis and Cytokinesis<br />
  2. 2. Objectives<br />Students will. . . .<br />Describe the structure and function of the spindle during mitosis<br />Summarize the events of the four stages of mitosis<br />Differentiate cytokinesis in animal and plant cells<br />
  3. 3. Chromatid Separation in Mitosis<br />Every second about 2 million new blood cells are produced in your body by cell divisions occurring in the bone marrow.<br />These cells have received the signal to divide. <br />The cells advance beyond the G2 phase and enter into the last two phases; mitosis and cytokinesis.<br />
  4. 4. Chromatid Separation in Mitosis<br />During mitosis, the nuclei divide to form two nuclei, each containing a complete set of the cell’s chromosomes.<br />
  5. 5. Chromatid Separation in Mitosis<br />During mitosis, the chromatids on each chromosome are physically moved to opposite sides of the dividing cell with the help of the spindle. <br />Spindles are cell structures made up of both centrioles and individual microtubule fibers that are involved in moving chromosomes during cell division.<br />
  6. 6. Forming the Spindle<br />At each of the cell’s poles lies a centrosome. <br />The centrosome is an organelle that organizes the assembly of the spindle.<br />In animal cells, a pair of centriolesare found inside each centrosome.<br />Centrioles and spindle fibers are both made of hollow tubes of protein called microtubules. <br />Each spindle fiber is made of an individual microtubule.<br />Each centriole however, is made of nine triplets of microtubules arranged in a circle.<br />
  7. 7. Mitosis and Cytokinesis<br />Although mitosis is a continuous process, biologists traditionally divide it into four stages<br />Step 1: Prophase<br />Step 2: Metaphase<br />Step 3: Anaphase<br />Step 4: Telophase<br />
  8. 8. Mitosis and Cytokinesis<br />Step 1: Prophase<br />Chromosomes coil up and become visible during prophase. <br />The nuclear envelope dissolves and a spindle forms.<br />
  9. 9. Mitosis and Cytokinesis<br />Step 2: Metaphase<br />During metaphase, the chromosomes move to the center of the cell and line up along the equator. <br />Spindle fibers link the chromatids of each chromosome to opposite poles.<br />
  10. 10. Mitosis and Cytokinesis<br />Step 3: Anaphase<br />Centromeres divide during anaphase. <br />The two chromatids (now called chromosomes) move toward opposite poles as the spindle fibers attached to them shorten.<br />
  11. 11. Mitosis and Cytokinesis<br />Step 4: Telophase<br />A nuclear envelope forms around the chromosomes at each pole. <br />Chromosomes, now at opposite poles, uncoil and the spindle dissolves. <br />The spindle fibers break down and disappear. Mitosis is complete.<br />
  12. 12. Cytokinesis<br />As mitosis ends with the cell nucleus being divided, cytokinesis begins.<br />During cytokinesis, the cytoplasm of the cell is divided in half, and the cell membrane grows to enclose each cell, forming two separate cells as a result.<br />The end result of mitosis and cytokinesis is two genetically identical cells where only one cell existed before.<br />Cytokinesis: the cytoplasm divides<br />
  13. 13. Cytokinesis<br />In plant cells and other cells that have rigid cell walls, the cytoplasm is divided in a different way.<br />In plant cells, vesicles formed by the Golgi Apperatus fuse at the midline of the dividing cell and form a cell plate.<br />Cell plate<br />
  14. 14. Cytokinesis<br />A cell plate is a membrane bound cell wall that forms across the middle of the plant cell.<br />A new cell wall than forms on both sides of the cell plate. <br />When complete, the cell plate separates the plant cell into two new plant cells.<br />Cell plate<br />
  15. 15. Key Concepts. . . .<br />During mitosis, spindle fibers drag the chromatids to opposite poles of the cell. <br />A nuclear envelope forms. <br />Each resulting nucleus contains a copy of the original cell’s chromosomes<br />Cytokinesis in animal cells occurs when a belt of protein threads pinches the cell membrane in half. <br />Cytokinesis in plant cells occurs when vesicles from the Golgi Apparatus fuse to form a cell plate.<br />
  16. 16. Computer Lab<br />Go to the computer lab. <br />Today’s assignment is to research the “Cell Cycle”, including mitosis and cytokinesis, and sequence the steps in order demonstrating the order of cell division. <br />Create a written 1 page with all the steps in order with a brief explanation of each step.<br /> Match this one written page to a diagram you have located online or created yourself demonstrating the complete cycle.<br />