1. Cell Division

2. Why? Cells divide for many reasons: – In order to stay small Diffusion occurs at a faster, more efficient rate in smaller cells. – DNA limits their size DNA can only control cells up to a certain size. – Repair/replace old or damaged cells. – Growth and Development We start out as one cell, mitosis allows that 1 cell to turn into billions of cells.

3. Cell Cycles Mitosis – Occurs in somatic (ordinary body cells) for growth and repair – Creates 2 identical cells Meiosis – Occurs in germ cells (ovaries and testes) to make gametes (sex cells). – Creates 4 similar cells.

4. Eukaryotic Cell Cycle 3 Stages – Interphase G1: First growth phase S: Synthesis phase G2: Second growth phase – Mitosis nuclear division – Prophase – Metaphase – Anaphase – Telophase – Cytokinesis Division of cytoplasm

5. Interphase  This is when the cell is preparing to divide.  The LONGEST phase of the cell cycle  90% of the cell’s life is spent in Interphase. G1 – first growth phase: – The cell doubles in size and the organelles double S – synthesis phase: – the DNA that makes up the chromatin is copied (DNA replication) this is the longest phase of interphase. G2 – second growth phase: – Growth and preparation for mitosis, second check-point. *Start Foldable

6. Interphase (G1, S, G2)

7. Mitosis (PMAT) Mitosis – The nucleus of a cell is divided into two nuclei with the same number of chromosomes. – Consists of 4 phases Prophase Metaphase Anaphase Telophase

8. Mitosis Step1: Prophase Longest phase of MITOSIS – Chromatin coils and forms chromosomes – Nuclear envelope breaks down – Spindle fibers form and stretch from one end of the cell to the other They attach to the centrioles They help to pull the cell apart

9. Mitosis Step2: Metaphase Chromosomes line up in the middle of the cell

10. Mitosis Step3: Anaphase Centromere of each chromosome splits Two sister chromatids separate and move to opposite poles Each chromatid becomes separate (non- replicated) chromosome in each daughter cell.

11. Mitosis Step4: Telophase Last stage of Mitosis Chromosomes at each pole uncoil and become chromatin Nuclear envelope reforms Spindle fibers break down

12. Cytokinesis NOT part of mitosis The cytoplasm divides into two cells Cell membrane reforms In plant cells the cell wall reforms

14. Name ___________________ Date ____________________ Period ___________________ Mitosis Foldable Interphase Prophase Metaphase Anaphase Telophase Cytokinesis