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Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210. According to the cell theory, where do all cells come from?. Cells divide to make a new identical cell. At this moment, cells in your body are growing, dividing, and dying. Section 8.2 Summary – pages 201 - 210.

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Section 8.2 Summary – pages 201 - 210

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  1. Section 8.2 Summary – pages 201 - 210 • According to the cell theory, where do all cells come from? • Cells divide to make a new identical cell.

  2. At this moment, cells in your body are growing, dividing, and dying. Section 8.2 Summary – pages 201 - 210 • Old cells on your scalp, palms of your hands, and soles of your feet are shedding and being replaced. • Cuts and bruises are healing • Your intestines are producing millions of new cells each second.

  3. Section 8.2 Summary – pages 201 - 210 • Early biologists noticed that just before cells divide, several short structures suddenly appeared in the nucleus. • Then they noticed that after cellular division that these structures would vanish.

  4. WAIT TO ANSWER: Where is DNA found in a eukaryotic cell? Section 8.2 Summary – pages 201 - 210 Nucleus • For most of a cell’s life, DNA exists in long strands called chromatin.

  5. CELL REPRODUCTION Section 8.2 Summary – pages 201 - 210 • Before a cell divides, chromatin coils up into tightly packed structures called chromosomes.

  6. Chromosome

  7. CELL REPRODUCTION Section 8.2 Summary – pages 201 - 210 • Chromosomes are the carriers of genetic material that is copied and passed from generation to generation of cells.

  8. CELL REPRODUCTION Section 8.2 Summary – pages 201 - 210 Before a cell can divide- a copy of all the chromosomes needs to be made so that the new “daughter” cell has the exact DNA as the “parent” cell. “Parent Cell” Chromosomes “Daughter Cell” Chromosomes

  9. TALK TO YOUR NEIGHBOR:(I will randomly call on someone in a few seconds) Chapter Assessment DNA can be very stringy and called _______ When a cell is about to divide, it coils up tightly and is now a “fatter” structure called _________

  10. TALK TO YOUR NEIGHBOR:(I will randomly call on someone in a few seconds) Chapter Assessment Why does a cell make a copy of it’s chromosomes before it divides and makes another cell?

  11. The Cell Cycle Section 8.2 Summary – pages 201 - 210 • The cell cycle is the sequence of growth and division of a cell. (life cycle) • The cell cycle consists of Interphase, Mitosis, and Cytokinesis

  12. The Cell Cycle Section 8.2 Summary – pages 201 - 210 • The majority of a cell’s life is spent in the growth period known as interphase.

  13. The Cell Cycle Section 8.2 Summary – pages 201 - 210 Interphase • During Interphase, under a microscope, there doesn’t appear to be much going on. • BUT, Interphase is the busiest phase of the cell cycle • During this time the cell is growing, making more organelles, and chromatin (DNA) is replicating. Replicated Chromatin Chromatin

  14. The Cell Cycle Mitosis • Following interphase, a cell enters its period of nuclear division called mitosis. • There are four phases in mitosis…

  15. Section 8.2 Summary – pages 201 - 210 PROPHASE: • The membrane around the nucleus and nucleolus disintegrate (disappear) 2. (In animal cells) centrioles begin to move to opposite ends of the cell and spindle fibers begin to form Nucleus Centrioles Spindle Fiber

  16. 3. Chromatin coils up to form visible chromosomes Section 8.2 Summary – pages 201 - 210 Replicated Chromatin Replicated Chromosome

  17. Section 8.2 Summary – pages 201 - 210 • The two halves of the doubled structure are called sister chromatids. • Sister chromatids are identical to each other. Sister chromatids

  18. Section 8.2 Summary – pages 201 - 210 • Sister chromatids are held together by a structure called a centromere, which plays a role in chromosome movement during mitosis. Centromere

  19. PROPHASE Section 8.2 Summary – pages 201 - 210

  20. Section 8.2 Summary – pages 201 - 210 METAPHASE: • The chromosomes move to the middle (equator) of the cell

  21. Section 8.2 Summary – pages 201 - 210 • Spindle fibers on attach to the centromeres on either side of the chromosome Centromere Spindle fibers

  22. METAPHASE Section 8.2 Summary – pages 201 - 210

  23. Section 8.2 Summary – pages 201 - 210 ANAPHASE: • The spindle fibers pull on the centromeres, break them, and pull the sister chromatids apart to either side of the cell- toward the centrioles.

  24. ANAPHASE Section 8.2 Summary – pages 201 - 210

  25. Section 8.2 Summary – pages 201 - 210 TELOPHASE: 1. Two complete cells are forming. 2. Chromosomes unravel back into chromatin 3. Nuclear membrane begins to re-appear around the chromatin

  26. TELOPHASE Section 8.2 Summary – pages 201 - 210

  27. The Cell Cycle Section 8.2 Summary – pages 201 - 210 Cytokinesis • Following telophase, the cell’s cytoplasm completely divides in a process called cytokinesis. • This is the final step in the cell cycle.

  28. The Cell Cycle Section 8.2 Summary – pages 201 - 210 Cytokinesis • Cytokinesis differs between plants and animals. • Toward the end of telophase in ANIMAL cells, the plasma membrane pinches in along the equator.

  29. The Cell Cycle Section 8.2 Summary – pages 201 - 210 Cytokinesis

  30. Cytokinesis Section 8.2 Summary – pages 201 - 210 • Plant cells have a rigid cell wall, so the plasma membrane does not pinch in. • A structure known as the cell plate is laid down across the cell’s equator.

  31. Result of Mitosis Section 8.2 Summary – pages 201 - 210 • When mitosis is complete, unicellular organisms remain as single cells.

  32. Result of Mitosis Section 8.2 Summary – pages 201 - 210 • Following mitosis, in multi-cellular organisms, cell growth and reproduction result in groups of cells that work together as tissue to perform a specific function.

  33. Control of Cell Cycle Section 8.3 Summary – pages 211 - 213 • Occasionally , cells lose control of the cell cycle. • Cancer is a growth resulting from uncontrolled cell division. • This loss of control may be caused by environmental factors or certain inheritances.

  34. Control of Cell Cycle Section 8.3 Summary – pages 211 - 213 • There are enzymes (proteins) that control the rate of the cell’s life cycle. • Scientists believe that if something goes wrong with these enzymes, they cause cells to skip a long interphase and divide a lot faster than they should.

  35. CANCER Section 8.3 Summary – pages 211 - 213 • A bunch of cancer cells together form masses of tissue called tumors that deprive normal cells of nutrients.

  36. CANCER Section 8.3 Summary – pages 211 - 213 • The causes of cancer are difficult to pinpoint because both genetic and environmental factors are involved. • Cancer may also be caused by viral infections that damage the genes.

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