Mitosis- the great divide (JW).ppt

The Great Divide 05/04 Why Would a Cell  As cells absorb Divide? nutrients and get larger, the volume of the cell increases faster than the surface area  This means that a cell can no longer absorb nutrients and get rid of wastes fast enough to support its demands (volume)  So what’s a cell to do...

The Great Divide 05/04 Why Would a Cell  As cells absorb Divide? nutrients and get larger, the volume of the cell increases faster than the surface area  This means that a cell can no longer absorb nutrients and get rid of wastes fast enough to support its demands (volume)  So what’s a cell to do? DIVIDE !!!! Why Would a Cell Besides growth a cell would also divide Divide? for:  Repair or Replacement  Cancer The Cell Cycle The Cell Cycle There are two parts to a cells life. interphase (growth & replication of DNA) mitotic phase (division of cell into 2 daughter cells)  Cell spends about 90% of the time in interphase Interphase Cell is absorbing nutrients, growing & doing its job. Cell continues to grow & duplicates its DNA. Mitosis: A Closer Look During Interphase: DNA is all twisted up into a Chromosome.  the Chromosome is then copied.  2 complete identical sets of chromosomes connected in the middle by a centromere are formed. The Mitotic  The 4 Stages of of Mitosis: Phase  Prophase  Metaphase  Anaphase  Telophase (+) PLUS  Cytokinesis Prophase  Chromatids condense becoming visible.  Nuclear membrane dissolves  The centrioles (an organelle that makes microtubules) appears and migrate to opposite sides.   spindle fibers start to form between them http://www.biostudio.com/demo_freeman_dna_coiling.htm Metaphase  Chromosomes line-up on the metaphase plate  Centromeres are attached to spindle fibers Anaphase  Spindle fibers contract  Centromeres divide  Sister chromatids are pulled away from each other towards the poles Telophase  The chromosomes reach the poles  Nuclear membranes form around the 2 new nuclei Cytokinesis  The cytoplasm distributed equally between the 2 new cells Animal Plant What Mitosis Actually Looks Like Interpha se Prophase Metaphas e Telophas e http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_gif2.html Anaphase http://science.nhmccd.edu/biol/bio1int.htm What Happens After Mitosis?  The cell returns to interphase  Chromosom es uncoil back into chromatin  The cycle repeats itself over & The Guarentee  The product of mitosis is 2 cells  The daughter cells are identical to each other & to the mother cell Why is this so important Moth er cell Identical daughter cells The Daughter Cells  In humans, the 2 daughter cells will have 46 chromosomes (23 pairs)  Each chromosome is said to have the same gene sequence Identical daughter cells