1. The Cell Cycle

2. What is the cell cycle? The Stages of the life of the cell Involve: 1. Metabolic activities 2. Division

3. Purpose of Cellular Division -Asexual reproduction of cells -Development of multicellular organisms -Repair and renew cells that die from normal wear and tear or accidents

4. Cell Division and DNA When cells divide, duplicate copies of DNA ( genome) Are sent to each cell In eukaryotes, the genome consists of several chromosomes In prokaryotes, the genome is often a single long DNA molecule (chromosome)

5. Every eukaryotic species has a characteristic number of chromosomes in the nucleus Human somatic cells ( body cells) have 46 chromosomes- 23 pairs When not packaged, DNA is a long, thin strand (chromatin) associated With proteins called HISTONES

6. Histones- protein spheres DRAW Video on structure

7. Structure terms (206-208) Daughter cell Genome Somatic Cells Gametes (germ cells) Chromosome Sister chromatids Chromatin Centromere Kinetochore Mitosis Cytokinesis

8. Chromosomes Each duplicated chromosome consists of two sister chromatids which contain identical copies of the chromosomes DNA As they condense, the region where the strands connect shrinks to a narrow area called the centromere Centromere

10. Stages of the Cell Cycle Divided into 2 main stages 1.Interphase- G1, S, G2 2.Mitotic Phase- M

11. Who are these guys?

17. Stages of the Cell Cycle 1.G1 phase- growth 2.S phase- “synthesis”, chromosomes copied 3.G2 phase- cell completes preparations for cell division 4.Mitosis- division of cells to 2 daughter cells

18. The Stages of Mitosis Prophase –Chromosomes condense and nuclear membrane disappears –Each chromosome appears as a sister chromatid- X SHAPE FORMATION –Mitotic spindle, consisting of microtubules and other proteins, forms between the two pairs of centrioles as they migrate to opposite poles of the cell. –THIS IS USED TO PULL THE CHROMOSOMES APART

19. Prometaphase –Breakdown of nuclear envelope into small fragments –Microtubules interact with the chromosomes –Bundles of microtubules extend from each pole toward the middle –Each of the 2 chromatids has a specialized structure called a kinetochore. Some microtubules attach to the kinetochore to begin movement The Stages of Mitosis Kinetochore

20. Metaphase –Centrosomes are now at opposite poles of the cell –Chromosomes convene on the metaphase plate-immaginary line between poles –Centromeres aligned and the kinetochores of the sister chromatids are attached to microtubules coming from opposite poles of the cell –The microtubules are called spindles b/c of their shape The Stages of Mitosis

21. Anaphase –Paired centromeres of each chromosome separate, freeing sister chromatids –Each chromatid is considered a full fledged chromosome –The once joined sisters begin to move towards opposite poles of the cell –By the end of anaphase, the 2 poles of the cells have equivalent and a complete collections of chromosomes The Stages of Mitosis

22. Telophase –Nonkinetochore microtubules elongate the cell, and daughter nuclei form at the poles of the cell –Nuclear envelopes arise from the fragments of the parent cell’s nuclear envelope –Chromatin fiber becomes less tightly coiled –CYTOKINESIS- division of cytoplasm takes place shortly after end of mitosis The Stages of Mitosis

23. Cytokinesis Cleavage furrow forms which pinches the cell into 2 parts, near the old metaphase plate. On the cytoplasmic side of the furrow is a contractile ring of microfilaments which contracts to pull apart the cells like a drawstring Finally 2 separate cells are created Video to wrap it up