1. Cell Cycle and Mitosis SBI3C @ RHSA

2. Why Do Cells Need to Divide? to grow bigger To replace cells that die or are damaged

3. How Long Does Cell Division Take? It depends on the type of cell. Examples: Human embryo cells (15-20 minutes) Skin cells (24 hours) Nerve cells (never) E.coli bacteria (24 hours)

4. Cell Cycle The cell cycle includes all of the steps a cell goes through from the time it is created until the time it divides. 2 Main Parts: 1. Interphase 2. Mitosis (followed by cytokinesis)

5. 1. Interphase A cell spends most of its time in interphase. During interphase the cell is very busy: 1. Growing 2. Making copies of its DNA and organelles

6. 1. Interphase (cont.) In order for chromosomes to be copied they must first unwind. During interphase, the nucleus looks like a dark blob (individual chromosomes are not visible when they are unwound).

7. Find onion cells in interphase!

8. 2. Mitosis Only a very short part of a cell’s life is spent in mitosis. During mitosis all of the cell’s chromosomes are evenly divided and they move to opposite ends of the cell

9. Mitosis has 4 Steps 1. Prophase chromosomes condense and become visible 2. Metaphase chromosomes line up along the middle of the cell 3. Anaphase chromosomes are pulled apart to opposite ends of the cell 4. Telophase the cell begins to pinch in the middle

10. Find cells undergoing prophase, metaphase, anaphase and telophase.

11. 3. Cytokinesis After mitosis, the cell divides all the cytoplasm and organelles in the process of cytokinesis. This is where one cell splits into two cells.

12. Online resources Mitosis animation http://www.cellsalive.com/mitosis.htm Mitosis videos http://www.sumanasinc.com/webcontent/animations/content/ mitosis.html http://www.sumanasinc.com/webcontent/animations/content/ mitosis.html http://www.biostudio.com/d_%20Mitosis.htm Mitosis quizzes http://school.discoveryeducation.com/quizzes6/muskopf/mito sis1.html http://school.discoveryeducation.com/quizzes6/muskopf/mito sis1.html http://www.phschool.com/science/biology_place/biocoach/mi tosisisg/quiz.htmlhttp://www.phschool.com/science/biology_place/biocoach/mi tosisisg/quiz.html http://local.brookings.k12.sd.us/biology/ch10celldivision/mito sis_review.htmhttp://local.brookings.k12.sd.us/biology/ch10celldivision/mito sis_review.htm