1 1 Mitosis and the Cell Cycle Big Idea: Mitosis is the process in which the nucleus divides to form two new nuclei and two cells with identical DNA.

How do little elephants grow up to be BIG elephants?

 The cell cycle is a repeated pattern of growth, division, and replacement that occurs in eukaryotic cells

 The cell cycle is a regular pattern of growth, DNA replication, and cell division.

 The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis. –Gap 1 (G 1 ): cell growth and normal functions Mitosis occurs only if the cell is large enough and the DNA undamaged. –DNA synthesis (S): copies DNA –Gap 2 (G 2 ): additional growth –Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)

Mitosis begins after fertilization 1 cell becomes 2 cells, becomes 4 cells…becomes TRILLIONS

Why do cells make more cells?

Animated Mitosis Cycle Interphase Prophase Metaphase Anaphase Telophase & Cytokinesis

Chromosomes are copied (# doubles) Chromosomes appear as threadlike coils ( chromatin ) at the start, but each chromosome and its copy( sister chromosome) change to sister chromatids at end of this phase CELL MEMBRANE Nucleus Cytoplasm

Animal Cell Plant Cell Photographs from:

Mitosis begins (cell begins to divide) Centrioles (or poles) appear and begin to move to opposite end of the cell. Spindle fibers form between the poles. Centrioles Sister chromatids Spindle fibers

Animal Cell Plant Cell Photographs from: Spindle fibers Centrioles

Chromatids (or pairs of chromosomes) attach to the spindle fibers. Centrioles Spindle fibers

Animal Cell Plant Cell Photographs from:

Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell. Centrioles Spindle fibers

Animal Cell Plant Cell Photographs from:

Two new nuclei form. Chromosomes appear as chromatin (threads rather than rods). Mitosis ends. Nuclei Chromatin

Animal Cell Plant Cell Photographs from: Cell Plate

Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.

Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase

Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase

I I nterphase P P rophase M M etaphase A A naphase T T elophase C C ytokinesis IPMATC I Prefer Meatloaf At Tennis Camp

24

25 - Cell Division 25