1 / 19

The Great Divide

Mitosis:. The Great Divide. 05/04. DO NOW…. THINK: How many cells are you composed of? When an organism grows bigger do you get more cells or just bigger cells or both? When do your cells divide the fastest? Slowest? Do cells ever stop dividing?. Why Would a Cell Divide?.

karenhay
Download Presentation

The Great Divide

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mitosis: The Great Divide 05/04

  2. DO NOW… THINK: • How many cells are you composed of? • When an organism grows bigger do you get more cells or just bigger cells or both? • When do your cells divide the fastest? Slowest? • Do cells ever stop dividing?

  3. Why Would a Cell Divide? • As cells absorb nutrients and get larger, the volume of the cell increases, and a cell can no longer absorb nutrients and get rid of wastes fast enough. • So what’s a cell to do? • Solution: divide in 2!

  4. When Would a Cell Divide? • Growth • Repair or Replacement • Cancer Different cells divide at different rates: • Most mammalian cells = 12-24 hours • Some bacterial cells = 20-30 minutes

  5. Getting Older… • All cells are only allowed to complete a certain number of divisions • Then they die (programmed cell death) How does cell division change over a lifetime? • Childhood = cell division > cell death • Adulthood = cell division = cell death • The Later Years = cell division < cell death

  6. The Cell Cycle

  7. Stages of the Cell Cycle • 2 stages = interphase (growth & replication of DNA) & mitotic phase (division of cell into 2 daughter cells) • Cell spends about 90% of the time in interphase

  8. Interphase • Divided into 3 phases: • G1 (1st gap) = small cell is absorbing nutrients, growing & making proteins • S (synthesis) = cell is continuing to grow & duplicates its DNA (i.e. chromosomes) in preparation for making duplicate cells during mitosis • G2 (2nd gap) = cell keeps grow- ing & making proteins; it grows toobig…solution = divide in 2

  9. The Mitotic Phase • Equal distribution of chromosomes (DNA) into 2 identical daughter cells • Divided into 4 stages of Mitosis: • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis

  10. Prophase • DNA condenses (gets shorter & thicker) so they are now visible • Appear as sister chromatids • Nuclear membrane dissolves • The centrioles move to opposite poles & spindle fibers form between them • http://www.biostudio.com/demo_freeman_dna_coiling.htm

  11. Metaphase • Chromosomes line-up along the center and attach to the spindle fibers

  12. Anaphase • Sister chromatids are pulled away from one another towards the poles

  13. Telophase • The chromosomes reach the poles • Nuclear membranes form around the 2 new nuclei

  14. Cytokinesis • The cytoplasm distributed equally between the 2 new cells • In animals, a cleavage furrow forms from outside in • In plants, a cell plate forms from inside out Plant Animal

  15. What Mitosis Actually Looks Like Interphase Metaphase Prophase Telophase Anaphase http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_gif2.html http://science.nhmccd.edu/biol/bio1int.htm

  16. What Happens After Mitosis? • The cell returns to interphase • Chromosomes uncoil back into thin strands of DNA • The cycle repeats itself over & over…

  17. At What Stage Are Our Cells At In The Cell Cycle? • Different cells can be in different stages • Interphase • Mitosis: • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis

  18. Can You Identify the Stages of Mitosis? Put the following mitosis stages in the correct sequence

  19. Identify the phase in the following 18 cells:

More Related