2. The Cell Cycle Every hour, approximately 1 billion of your cells die – but approximately 1 billion cells are created in a process of cell division called mitosis.

3. Why Do Cells Divide?

4. Why Do Cells Divide 1.Healing and Tissue Repair An average human looses 105 pounds of dead skin cells in their life Every second, millions of your body cells are injured or die and must be replaced Replacement of dead cells also occurs in plants

5. Why Do Cells Divide 2.Growth All plants and animals begin life as a single cell Only two ways for an organism to grow: 1) single cell gets bigger; or 2) the single cell divides into more cells

6. Why Do Cells Divide One of the most important jobs of a cell is to exchange materials with its environment (the body or outside world) The cell needs to get food and nutrients in and waste out

7. Why Do Cells Divide Why Don’t Cells Just Keep Getting Bigger? Eventually a cell will reach a size where it will not be able to get enough exchange of materials to sustain cell function

8. Why Do Cells Divide 3.Perpetuate Life Important for unicellular (prokaryotes) organisms like bacteria – creates 2 new organisms

9. Why Do Cells Divide 3.Perpetuate Life Also essential for reproduction of multicellular organisms

10. The Cell Cycle The repeating cycle in the life of a cell Interphase : when a cell is preparing for cell division; this is the majority of the time Cell division : the process of 1 cell dividing into 2 cells Mitosis: division of the nucleus Cytokinesis : division of the cytoplasm

12. Interphase First Growth Phase (G 1 ) Period of growth for a cell Produces new proteins and organelles Synthesis Phase (S) Cell synthesizes entire copy of DNA Second Growth Phase (G 2 ) – shortest phase Cell produces organelles and structures for cell division

13. Mitosis: What is it basically? DNA copies (chromosomes) are separated & sorted into two sides of the cell the cell then splits in two and part of each parent is carried to the two new cells. each ‘daughter’ cell is identical to the parent cell results in cells such as internal organs, skin, bones, blood, etc. Mitosis animation: http://www.youtube.com/watch?v=2WwIKdyBN_s&feature=related http://www.youtube.com/watch?v=2WwIKdyBN_s&feature=related

14. Interphase occurs just before Mitosis begins: DNA is replicated along with organelles and other cellular components and the cell prepares for division. http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm

15. Before Mitosis : Interphase Animal cellPlant cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

16. 1 st step in Mitosis: Prophase (preparation phase) http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm the DNA recoils, and the chromosomes condense the nuclear membrane disappears mitotic spindles begin to form.

17. Mitosis Prophase Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Animal cell Plant cell

18. 2 nd step in Mitosis: Metaphase (organizational phase) spindle fibres attach to the chromosomes at the centromere chromosomes line up the middle of the cell http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm

19. Mitosis Metaphase Animal cellPlant cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

20. 3 rd step in Mitosis: Anaphase (separation phase) the chromosomes split at the centromere the ‘sister ‘chromatids are pulled by the spindle fibers to opposite poles of the cell. http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm

21. Mitosis Anaphase Animal cell Plant cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

22. 4 th step in Mitosis: Telophase the chromosomes, the cytoplasm and organelles divide into 2 portions. this diagram shows the end of telophase. http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm

23. Mitosis Telophase Animal cellPlant cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

24. After Mitosis: Cytokinesis the actual splitting of the daughter cells into two separate cells is called cytokinesis occurs differently in both plant and animal cells. Beginning of cytokinesis in a plant: Beginning of cytokinesis in an animal: http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm

25. MITOSIS

26. Mitosis http://www.youtube.com/watch?v=2WwIKdyBN_s&feature=related http://www.youtube.com/watch?v=VlN7K1-9QB0 http://www.cellsalive.com/mitosis.htm http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_gif2.html http://www.teachersdomain.org/resource/tdc02.sci.life.stru.dnadivide/ http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_ and_cytokinesis.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_ and_cytokinesis.html

27. Your task will be to identify the structures that will allow you to identify each phase and then to observe mitosis in a prepared slide of an onion root tip.

28. The Cell Cycle Remember iPMATc Interphase Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

29. Homework 1.Describe the events in the cell cycle. 2.Explain how mitosis ensures genetic continuity. 3.How does mitosis make the growth and repair of cells possible in an organism? 4.Get a textbook and describe each phase of mitosis along with a picture (pg. 30-32) Also define cytokinesis and apoptosis