1. Nematoda Secernenta in Anaphase Contributed by Richard J. Harris courtesy of BIODIDAC

2. 1. Mitosis- division of the cell nucleus 2. Cytokinesis- division of the cytoplasm

3. SEM image of Chromosomes

4. 1. Chromosomes- contain DNA (genetic info) which is passed from parent to offspring. 2. Before a cell divides each chromosome is copied

5. 3. Structure of the chromosome: * Two sister chromatids; are identical * Centromere- holds the sister chromatids together resulting in an x-shaped c’some Sister chromatids Centromere

6. * When the cell divides, the chromatids separate. * Each new cell gets one chromatid. Cell division Micrograph

8. 1. Cell Cycle- the series of events that takes place in a cell leading to its division & replication 2. During the cell cycle: * a cell grows * prepares for division 3. Divides to form two daughter cells, each of which begins the cycle again

9. 4. The cell cycle consists of four phases: * G1 (First Gap Phase) * S Phase (Synthesis) * G2 (Second Gap Phase) * M Phase (Mitosis)

11. 1. Interphase- the first stage of the cell cycle. During this phase the cell: * Grows * Makes new proteins & organelles * C’somes are replicated * DNA is made 2. Interphase has 3 phases: G1, S, & G2

12. 3. During G1, the cell: * increases in size * synthesizes new proteins and organelles 4. During the S phase: * chromosomes are replicated * DNA synthesis takes place 5. Once a cell enters the S phase, it usually completes the rest of the cell cycle

13. 6. The G2 Phase (Second Gap Phase) * organelles & molecules required for cell division are produced * Once G2 is complete, the cell is ready to start the M phase— Mitosis

16. 1. Mitosis has 4 phases: * Prophase * Metaphase * Anaphase * Telophase

17. 2. Centrioles- barrel shaped structures that are made of groupings of microtubules

18. 3. Spindle- a fanlike microtubule structure that helps separate the chromosomes.

19. 4. Chromatin- a combination of DNA and proteins that make up c’somes

20. 5. Prophase * The 1 st & longest phase of mitosis * The centrioles separate & end up on opposite sides of the nucleus in an area called the centromere * Chromatin condenses into chromosomes. * The nuclear envelope breaks down. A cell in prophase of mitosis. (An epithelial cell in prophase of mitosis, treated with the anti-cancer drug taxol. Chromosomes are labeled blue. Taricha granulosa (newt) lung.) Observing Mitosis with Fluorescence Microscopy. Prophase. © 1995-2013 by Michael W. Davidson and The Florida State University.

21. 6. Metaphase * 2 nd phase of mitosis * The chromosomes line up across the center of the cell * Microtubules connect the centromere of each chromosome to the poles of the spindle. Observing Mitosis with Fluorescence Microscopy. Metaphase. © 1995-2013 by Michael W. Davidson and The Florida State University.

22. 7. Anaphase * 3 rd phase of mitosis * the duplicated centromeres of each pair of sister chromatids separate * the now-daughter chromosomes begin moving toward opposite poles until they have separated into two groups. Observing Mitosis with Fluorescence Microscopy. Anaphase. © 1995-2013 by Michael W. Davidson and The Florida State University

23. 8. Telophase * The last phase of mitosis * Chromosomes gather at opposite ends of the cell * A new nuclear envelope forms around each bunch of chromosomes. Observing Mitosis with Fluorescence Microscopy. Telophase. © 1995-2013 by Michael W. Davidson and The Florida State University.

24. 9. Cytokinesis * the cytoplasm pinches in half. * Each daughter cell has an identical set of duplicate chromosomes. Actin (blue) and microtubules (orange) at the end of cytokinesis in a green urchin zygote. University of Washington Center for Cell Dynamics

25. * structure known as the cell plate forms midway between the divided nuclei * The cell plate gradually develops into a separating membrane. * A cell wall then begins to appear in the cell plate. Cell wallCell plate

26. * A cleavage furrow forms-An indention formed by microfilaments * The pulling of the filaments separates the cytoplasm of the daughter cells

27. * 95% of the cell cycle is spent in interphase * A typical rapidly dividing human cell with a total cycle time of 24 hours: * the G1 phase might last about 11 hours * S phase about 8 hours * G2 about 4 hours * and M about 1 hour.

28. * Page 249 “Analyzing Data- The Life Span of Human Cells” * Read the paragraph and answer questions 1-4