Cell Cycle and Mitosis Page: 51 and 52

What is the cell cycle? Continuous sequence of events that takes place in eukaryotic cells Starts when a cell is formed Continues until cell has divided into 2 new cells

Interphase Longest phase of the cell cycle Cells are metabolizing and growing 3 parts: G1 S G2

Interphase: G1 G1 = growth phase 1 Growth and metabolism Draw picture of Interphase – Label 1) Cell Membrane = Outer layer of the cell; 2) Nuclear membrane = Layer around the light purple circle 3) Chromatin = stringy looking inside of nucleus; 4) Centrioles = Yellow cylinders

Interphase: S S = synthesis DNA is replicated (doubled)

Interphase: G2 G2 = growth phase 2 Slower growth and metabolism Organelles duplicated Preparing for cell division

Interphase: G0 G0 phase = Resting phase Not dividing or preparing to divide May reenter the G1 cycle, but often it continues in G0 until the organism dies

Mitosis

Mitosis Mitosis is normal cell division, creates two identical cells. Cell division occurs throughout your life. Three reasons why multicellular organisms do mitosis: 1. Growth 2. Repair 3. Replacement

Why would a Unicellular organism do cell Division? To reproduce!

Prophase - “primary = 1st” Chromosomes condense and become visible Nuclear membrane breaks down to let chromosomes out Centrioles and spindle fibers move chromosomes opposite towards poles Draw prophase: Label 1) Nuclear membrane = Dotted Circle; 2) Spindle Fibers = string/spider looking structures 3) Condensed Chromosomes = blue and red structures

Metaphase “Think Middle” Chromosomes line up along equator Spindle fibers firmly attach to centromeres . . . . . Draw Metaphase 1) Label Centromeres = Black dots in middle of chromosomes

Anaphase “Away” Centromeres break Chromatids move to poles Guided/pulled by spindle fibers Draw Anaphase: Label 1) Chromatids = V –shaped 2) Spindle Fibers = lines pulling 3) Centromeres = broken, being pulled by spindle fibers

Telophase “two” Chromosomes reach poles Spindle fibers and centrioles disappear Nuclear membrane forms and nucleus reappears Chromosomes uncoil and disappear Draw Telophase - Label: 1) Nuclear membrane reforming 2) Chromosomes uncoiling

Cytokinesis = 2 identical daughter cells Cytoplasm divided between cells New cell membrane forms in animal cells New cell wall forms in plant cells Result: 2 identical diploid cells Diploid = 2 sets of chromosomes Haploid = 1 set of chromosomes Draw 2 identical daughter cells - Label: 1) Cell Membrane (2 cell membranes around each cell) 2) Nuclear membrane = dotted circle 3) Chromatin = string looking structures inside nucleus

Summary of Mitosis Prophase: Metaphase Anaphase Telophase Chromosomes condense Nuclear envelope disappears centrosomes move to opposite sides of the cell Spindle forms and attaches to centromeres on the chromosomes Metaphase Chromosomes lined up on equator of spindle centrosomes at opposite ends of cell Anaphase Centromeres divide: each 2-chromatid chromosome becomes two 1-chromatid chromosomes Chromosomes pulled to opposite poles by the spindle Telophase Chromosomes de-condense Nuclear envelope reappears Cytokinesis: the cytoplasm is divided into 2 cells

Vocab review: pg. 46 from ISN Spindle Fibers = attach to centromeres to pull chromosomes apart Nuclear membrane = stores chromosomes; must dissolve to let chromosomes move Chromatin = DNA in its uncondensed form

Vocab review: pg. 46 from ISN Histone Proteins = Used to wind up chromatin to form chromosomes Chromosomes = condensed DNA; Contains 2 copies of chromatids Chromatids = replicated chromosomes Daughter cells = result of mitosis; 2 identical cells