Cell Growth & Reproduction MITOSIS

1. Cell Growth & ReproductionMITOSIS

2. Cell Growth • When a living thing grows it does so by producing more cells INSTEAD of making the cells it has larger • Whether it be elephant, human, jellyfish or earthworm – all the cells are about the same size • There are two reasons why this happens: • DNA Overload • Exchange of Materials

3. DNA Overload Exchange of Materials • All the information to run a cell is located in the nucleus as a code of DNA • If the cell were to get bigger and bigger there would not be enough “information” to run the whole cell • The cell must transport everything it needs through the membrane • If there isn’t enough membrane space, cells can’t get or get rid of what they need. • So there must be a balance between surface area (room to move stuff in & out) and volume (stuff) Why are cells so small?

4. Why must cells divide? • What does the Cell Theory say? • 3 Major Reasons Cells Divide: • Growth – you start as one cell • Development – you get bigger, learn & change • Repair – your cells get worn out

5. What does a cell need to survive? • A FULL set of genetic material (DNA or RNA) • Biggest hurdle to cell division is making sure each cell transfers ALL the DNA when it makes new cells • This gets more difficult as there becomes more DNA to transfer

6. A Cell’s Life A cell’s life can be divided into 2 stages: • Interphase (3 Parts) – Non-dividing stages • Gap 1 (G1) • Growth phase #1 – cells get bigger • Most cells are found in this phase – “Normal Cells” • Synthesis (S) • New DNA is synthesized, or made • Gap 2 (G2) • Growth phase #2 • Preparations for division are made • Mitosis (4 parts) – Dividing stages • Prophase • Metaphase • Anaphase • Telophase

8. Cell Cycle: Interphase • Three phases of Interphase: • G1 – growing, increasing in size, synthesis of new proteins and organelles • S phase – Chromosomes are duplicated • G2 – shortest phase, synthesis of organelles and molecules needed for cell division

9. Mitosis – Prophase • Prophase • Chromatin condenses to Chromosomes • chromatids are joined by centromere • Centrioles move to opposite ends of cell • Nucleolus disappears • Nuclear membrane dissolves

10. Mitosis – Metaphase • Chromosomes line up at the equator • Chromosomes attach to spindle fibers (from the centrioles) at centromeres

11. Mitosis – Anaphase • Chromosomes get pulled apart • Spindle fibers shorten and pull sister chromatids to the opposite ends of the cell

12. Mitosis – Telophase • Chromosomes de-condense • Spindle fibers disintegrate • Nuclear membrane forms • Nucleolus becomes visible • Animal Cells – a contractile ring forms around the middle of the cell • Plant cells – a band of cytoskeletal proteins called the cell plate forms

13. Cytokinesis – division of the cytoplasm • Animal Cells – the contractile ring pinches • in the middle to fuse the membrane and • separate the new nuclei • Plant Cells – a new section of cell wall • forms from the cell plate, between the nuclei • to form two distinct cells

15. A B C

16. D E

18. This is a complicated process… what happens when things go wrong? • There are several factors that try to control the cell cycle: • Before a cell divides the DNA is checked to make sure it was replicated correctly • Chemical signals tell a cell when to start and stop dividing • http://www.cancerquest.org/index.cfm?page=193 • Cells also communicate to neighboring cells to tell them to stop growing • http://www.cancerquest.org/index.cfm?page=2463

19. Cancer

20. True or False? Cancer is contagious. True or False Cancer is one disease. True or False Cancer spreads with surgery. True or False cancer is inherited. True or False Cancer hurts. True or False cancer leads to death. True or False All tumors are cancerous. True or False The medical community is keeping the cure for cancer a secret, so the doctors can make more money. True or False