1. Cell Division

2. Lifespan of Cells Can you guess how often these cells to divide? Red Blood Cell = Stomach Cell = Skin Cell = Liver Cell = Muscle Cell = Nerve Cell = Every 120 days Every day Every day; new skin each month Every year Rarely divide; just grows bigger Rarely divide after birth

3. Why do cells divide? To replace dying cells To pass on genetic material THINK! – What is our genetic material? THINK! – How many DNA molecules does a human body cell have? THINK! – Does every organism have the same number of DNA molecules? DNA 46 NO

4. The Cell Cycle Cell Cycle - the time it takes for a cell to grow & divide Cell Cycle has 3 stages: Interphase : time where cell grows bigger & copies or replicates each DNA molecule Mitosis : time where cell divides out its DNA molecules so each new cell receives the same number Cytokinesis : time where cell divides its cytoplasm and organelles

5. Diagram of Cell Cycle

6. Learning Terminology! Chromatin DNA molecules that are loose and thread-like seen during interphase HINT – Chromatin is very thin! Chromosomes DNA molecules that are tightly coiled up Seen during mitosis Duplicated Chromosomes THINK! – When does each DNA molecule double? When DNA doubles each molecule has an identical twin These twins stay attached at a point called the centromere Interphase

7. Label the Diagram ChromatinChromosome Duplicated Chromosome THINK! – Why would a cell want to coil up its DNA before it divides? Easier to divide

8. Interphase THINK! – What 2 things happen during interphase? Cell grows Cell replicates (doubles) its DNA

9. Mitosis (4 Phases) The cell divides the DNA molecules inside its nucleus so that each cell gets the same number of DNA molecules as the original cell THINK! – A mosquito normally has 6 DNA molecules. How many molecules will each cell have after mitosis? THINK! – Humans normally have 46 DNA molecules. How many molecules will each cell have after mitosis? 6 46

10. Phase 1: Prophase Nickname – “P” for Prepare Chromatin condenses into chromosomes Nuclear membrane disappears Spindle fibers appear Think of spindle fibers like fishing line. They attach to the centromere & pull the chromosomes to opposite ends of the cell.

11. Phase 2: Metaphase Nickname – “M” for Middle Spindle fibers move the duplicated chromosomes into the middle of the cell THINK! – Why do you think the duplicated chromosomes line up in the middle? So that the cell can easily check to make sure all the chromosomes are there

12. Phase 3: Anaphase Nickname – “A” for Apart Duplicated chromosomes split at the centromere Spindle fibers pull the chromosomes to opposite ends of the cell

13. Phase 4: Telophase Nickname – “T” for Tear Chromosomes uncoil back into chromatin Nuclear Membrane reappears Spindle fibers disappear THINK! – Telophase is the complete opposite of what other phase in mitosis? prophase

14. Cytokinesis THINK! – What 2 things happen in cytokinesis? Cytoplasm divided between 2 cells Organelles divided between 2 cells

15. Cytokinesis: Animal vs. Plant Cytokinesis in Animal Cells Cell membrane pinches in to form 2 new cells Just like pinching in the middle of a water balloon Cytokinesis in Plant Cells Cell plate forms in center & new cell wall forms There is NO pinching inward !

16. Visualizing Mitosis! ACTIVITY INTERACTIVE ACTIVITY TO TRY WITH THE CLASS! Mitosis Hybrid Medical Animation http://hybridmedicalanimation.com/anim_mitosis.html Mitosis with Music http://www.loci.wisc.edu/outreach/bioclips/CDBio.html Brain-Pop Clip (Mitosis) http://glencoe.mcgraw-hill.com/sites/007877800x/student_view0/brainpop_movies.html# Streaming Animations Glencoe Mitosis Animation United Streaming (Mitosis_ 1:18) Real-Time Animations Animal Cell Mitosis (Just click on “LIVE ANIMAL MITOSIS”) http://iknow.net/CDROMs/cell_cdrom/index.html Plant Cell Mitosis (Just click on “PLANT CELL MITOSIS”) http://iknow.net/CDROMs/cell_cdrom/index.html Helpful Websites Cells Alive - http://www.cellsalive.com/mitosis.htmhttp://www.cellsalive.com/mitosis.htm Biology Corner http://www.biologycorner.com/bio1/cellcycle.htmlhttp://www.biologycorner.com/bio1/cellcycle.html