Making more cells, so life can continue CELL DIVISION Making more cells, so life can continue

Chromosomes Cell division involves copying chromosomes (DNA) and then dividing them among cells

Chromosomes 2 Types: Autosomes: chromosomes not directly involved in determining gender (22 pairs- in humans) Sex chromosomes: chromosomes directly involved in determining gender (1 pair- XX [girl] or XY [boy]) *23 pairs of chromosomes in humans- 46 total chromosomes

2 Types of Cell Division Mitosis- occurs in regular body cells of an organism (ex. Skin cells) Meiosis- occurs in the gametes (sex cells) of an organism (ex. Sperm and Eggs)

Cell Cycle Cell cycle: repeating sequence of cellular growth and division during an organism’s life make more cells

Steps of Mitosis 0) Interphase: G1: Chromosomes are not visible; cell is growing S: Chromosomes replicate (DNA synthesis) Each chromosome is now made of TWO sister chromatids joined at a centromere Same # of chromosomes, just double genetic info. G2: Centrioles and other organelles replicate

Interphase Video

Steps of Mitosis 1) Prophase (START of Mitosis) Chromosomes condense; now visible Nuclear Membrane disappears Centrioles migrate to poles (opposite ends of cell); spindle fibers form between them

Prophase Video

Steps of Mitosis 2) Metaphase Chromosomes attach to spindle fibers at centromere Spindle fibers pull the chromosomes to the middle of the cell

Metaphase Video

Steps of Mitosis 3) Anaphase Spindle fibers shorten Sister chromatids are pulled apart; opposite ends of cell

Anaphase Video

Steps of Mitosis 4) Telophase Nuclear Membrane reforms Spindle fibers disappear Chromosomes uncoil (invisible)

Telophase Video

Steps of Mitosis 5) Cytokinesis Cell splits in TWO as cell membrane encloses each new cell Two genetically identical diploid* cells *Diploid= 2 sets of chromosomes

Mitosis Video QUIZ

Cancer and Cell Division CancerQuest Video Read pg. 126 in text How does cancer relate to cell division? In what ways could scientists keep cancer cells from dividing/spreading? What preventive measures can reduce the chances of getting cancer? 11 minute video

References Mitosis and Meiosis. Ancient Lights. 1994. Discovery Education. 17 November 2009 <http://streaming.discoveryeducation.com/> Johnson & Raven. (2007) Biology. (CA ed.) Holt, Rinehardt, Winston. Austin, TX. Mitosis pictures: http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html