Cellular Division: Mitosis (Text Ch. 10, pp )

Reasons for Cell division  Basis of reproduction for all cellular organisms  Enables multicellular organisms to grow  Replaces worn-out or damaged cells and tissue

“Analysing Data”, p. 249  Life Span of Human Cells –1. White blood cells: function vs lifespan –2. Consequences of injury to heart + spinal cord? Smooth muscle? –3. Hypothesis for data –4. Cancer: predict data table

Summary of Cell division  Prior to division, cell replicates all of its DNA –One complete copy will go to each “daughter” cell

Recall:  genetic info for eukaryotic cells is contained in a membrane-bound nucleus  Before the cell can divide, the nucleus must also divide

Recall:  Two types of cell division: –1. Mitotic  46 double  46 single chromosomes  Asexual, body cells –2. Meiotic  46 double  23 single chromosomes  Sexual cells

Two Main Stages of Cell Division  1. Mitosis: –division of the nucleus –forms 2 daughter nuclei –each has a full, identical chromosome set  2. Cytokinesis: –division of the cytoplasm b/w 2 daughter cells

Cell Cycle  Interphase ~ 90% of time  Mitotic phase ~10% of time

Nucleus contains DNA and proteins  DNA packed tightly into chromatin fibres  Chromatin: – DNA coiled around histone molecules (protein) –Coils are then coiled into long fibres  Fibres dispersed throughout nucleus

Chromosome Structure Fig , p. 297

Chromosome Formation during Mitosis  Chromatin fibres gather + coil  Bunched into compact chromosomes  Set # of chromosomes per sp.

Interphase  Cell growth (G1)  DNA synthesis (S) –Chromosomes duplicate, still loosely packed  Produces proteins + organelles for div. (G2)

Prophase  Chromatin fibres condense into chromosomes –two “sister” chromatids –attached at a narrow waist (centromere)  Spindles form

Prophase, cont’d  Centrioles at poles  Spindles grow, reach chromosomes  Nuclear envelope breaks down & disappears

Metaphase  Chromosomes line up along metaphase plate at centre  Each chromatid connected at centromere to a spindle fibre from each pole

Anaphase  Centromeres split as spindle fibres pull chromatids apart  Form group of single chromosomes at each pole  Cell elongation begins

Telophase  Cells elongate  Daughter nuclei appear at each pole as envelope re-forms  Chromatin fibres uncoil

Telophase and Cytokinesis  Cleavage furrow (animal) –Cell plate (plant)  Cells contain ½ the cytoplasm, but same # chromosomes as parent cell

Mitosis in action:  urce/tdc02.sci.life.stru.dnadivide/ urce/tdc02.sci.life.stru.dnadivide/ urce/tdc02.sci.life.stru.dnadivide/  “Go Online” (p. 245 text)

Controls on Cell Division  Cell activity controlled by proteins (e.g. cyclins) and other regulators –E.g. healing a cut  What might happen without controls? –E.g. Cancer – how does it work? – UcjSPkLs&feature=related UcjSPkLs&feature=relatedhttp:// UcjSPkLs&feature=related