1. State that mitosis occupies only a small percentage of the cell cycle and that the remaining percentage includes the copying and checking of genetic information. State that mitosis occupies only a small percentage of the cell cycle and that the remaining percentage includes the copying and checking of genetic information. Explain the significance of mitosis for growth, repair and asexual reproduction in animals and plants. Explain the significance of mitosis for growth, repair and asexual reproduction in animals and plants. Describe, with the aid of diagrams, the stages of mitosis. Describe, with the aid of diagrams, the stages of mitosis. Module 1 - Cells 1.1.3 Cell Division

2. The Cell Cycle Each cell goes through a regular life cycle, similar to the cycle of life in humans. The major cell stages are interphase, mitosis, and cytokinesis.

3. Interphase Interphase consists of: G 1 = growth and preparation of the chromosomes for replication, new cell organelles are synthesised (approx 10 hours). G 1 = growth and preparation of the chromosomes for replication, new cell organelles are synthesised (approx 10 hours). S = synthesis of DNA, amount of DNA doubles (approx 9 hours). S = synthesis of DNA, amount of DNA doubles (approx 9 hours). G 2 = preparation for mitosis, centrioles replicate and spindle starts to form (approx 4 hours). G 2 = preparation for mitosis, centrioles replicate and spindle starts to form (approx 4 hours).mitosis When a cell is in any phase of the cell cycle other than mitosis, it is often said to be in interphase.

4. Interphase A normal resting cell exists in a state called interphase in which the chromatin is undifferentiated in the heavily-stained nucleus.

5. Interphase

6. Before the cell enters the mitosis phase, it first undergoes a synthesis or S phase where each chromosome is duplicated and consists of two sister chromatids joined together by a specific DNA sequence known as a centromere.

7. Mitosis Mitosis is cell division. Mitosis is cell division. The genetic purpose of mitosis is to produce two daughter cells that are genetically identical to the parent cell. The genetic purpose of mitosis is to produce two daughter cells that are genetically identical to the parent cell. Mitosis occupies a small percentage of the cell cycle. Mitosis occupies a small percentage of the cell cycle.

8. Prophase Tiny bundles of protein called centrioles start moving to opposite ends of the cell.Tiny bundles of protein called centrioles start moving to opposite ends of the cell. The mitotic spindle forms.The mitotic spindle forms. The chromosomes become shorter and more compact.The chromosomes become shorter and more compact. Nuclear membrane begins to disappear. Nuclear membrane begins to disappear. At the end of prophase, each chromosome can be seen to consist of two chromatids, held together by a centromere. At the end of prophase, each chromosome can be seen to consist of two chromatids, held together by a centromere.

9. Prophase

10. Metaphase The chromosomes, attached to the spindle by the centromere, begin to align along the equator, halfway between the spindle poles.

11. Metaphase

12. Anaphase During anaphase the sister chromatids separate and are moved toward the poles of the spindle, centromeres first. During anaphase the sister chromatids separate and are moved toward the poles of the spindle, centromeres first. The movement is a result of the spindle fibres contracting and shortening. The movement is a result of the spindle fibres contracting and shortening.

13. Anaphase

14. Telophase Chromosomes uncoil to become long and thin. Chromosomes uncoil to become long and thin. The mother cell is physically divided into two daughter cells by cytokinesis. The mother cell is physically divided into two daughter cells by cytokinesis. New nuclear membranes are formed. New nuclear membranes are formed.

15. Telophase

17. Why is mitosis important? Mitosis will result in cells which are exact copies of the parent cells. The daughter cells will contain the same number of chromosomes and be genetically identical to the parent. Mitosis is needed for: Growth – in order to grow new cells must be formed, identical to original cells. Growth – in order to grow new cells must be formed, identical to original cells. Repair of tissues – Damaged cells must be replaced by identical ones. Repair of tissues – Damaged cells must be replaced by identical ones. Asexual reproduction – results in offspring being genetically identical to the parent. Asexual reproduction – results in offspring being genetically identical to the parent.

18. Useful websites for Mitosis www.biologycorner.com/bio1/cellcycle.html www.biologycorner.com/bio1/cellcycle.html www.biologycorner.com/bio1/cellcycle.html www.cellsalive.com/mitosis.htm www.cellsalive.com/mitosis.htm www.cellsalive.com/mitosis.htm micro.magnet.fsu.edu/.../mitosis/mitosis.html micro.magnet.fsu.edu/.../mitosis/mitosis.html micro.magnet.fsu.edu/.../mitosis/mitosis.html www.johnkyrk.com/mitosis.html www.johnkyrk.com/mitosis.html www.johnkyrk.com/mitosis.html www.biologylessons.sdsu.edu/classes/lab8/g lossary.html www.biologylessons.sdsu.edu/classes/lab8/g lossary.html www.biologylessons.sdsu.edu/classes/lab8/g lossary.html www.biologylessons.sdsu.edu/classes/lab8/g lossary.html

19. Mitosis animations: www.johnkyrk.com/mitosis.html www.johnkyrk.com/mitosis.html www.johnkyrk.com/mitosis.html http://www.cellsalive.com/mitosis.htm http://www.cellsalive.com/mitosis.htm http://www.cellsalive.com/mitosis.htm

20. Meiosis Cell division of the gametes sperm and ovum. Cell division of the gametes sperm and ovum. Results in 4 haploid chromosomes genetically different to mother cell. Results in 4 haploid chromosomes genetically different to mother cell. This gives rise to variation within species. This gives rise to variation within species.