Cell Growth and Division The Cell Cycle & Mitosis

¿ Are cells always dividing? Sometimes they are growing Sometimes they are preparing to divide Sometimes they are dividing

Cell Division = Mitosis During life, we go from one cell to ~ 75 trillion cells. Mitosis = division of body cells Cancer = uncontrolled cell division

Cells that rarely divide Mature skeletal muscle cells Nerve cells

Cells that constantly divide Skin cells Cells that line gastro-intestinal tract

Cell cycle = Period of time between one cell division & the next

Cell cycle – Phases I. Interphase G1 - rapid cell growth - basic cell f(x)s

I. Interphase S = Synthesis – DNA replication G2 = Organelles & cytosol made G1 S G2

Cell cycle - Phases II. Mitosis = cell division III. Cytokinesis = cytoplasm division ?s 1-7

Sequence of Cell Cycle Interphase Prophase Metaphase Anaphase Telophase

(division of cytoplasm) Mitosis Includes : Prophase Metaphase Anaphase Telophase Cytokinesis (division of cytoplasm)

Cell during Interphase : DNA in form of chromatin Looks like hair / spaghetti (chrs. * not visible) * chromosomes

Prophase Chrs. coil and become visible Sister chromatids move towards poles Spindle forms Nuclear envelope & nucleoli disappear

Metaphase Sister chromatids line up at equator on metaphase plate (Meet me in the middle)

Anaphase Centromeres divide, chromatids split Sister chromatids move to opposite poles (centrioles) (Run away, run away!)

Telophase Chrs. uncoil and become invisible (now in form of chromatin) Spindle disappears Nuclear envelope & nucleoli re-appear

Cytokinesis Division into two identical DAUGHTER CELLS Starts during Telophase Finishes after Telophase is over animation

Whitefish cells during mitosis