1. Cell Division

2. Section 8.2 Summary – pages 201 - 210
Cell Division
Cell division is the process by which new cells are produced from one cell.
Cell division results in two cells that are identical to the original, parent cell.
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3. Section 8.2 Summary – pages 201 - 210
Chromosomes
Chromosomes are the carriers of the genetic material that is copied and passed from generation to generation of cells.
Accurate transmission of chromosomes during cell division is critical.
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4. Section 8.2 Summary – pages 201 - 210
The structure of eukaryotic chromosomes
Sister chromatids
Centromere
Continued coiling within supercoil
Supercoil within chromosome
Chromosome
DNA
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5. Section 8.2 Summary – pages 201 - 210
The Cell Cycle
The cell cycle is the sequence of growth and division of a cell.
The majority of a cell’s life is spent in the growth period known as interphase.
Interphase
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6. Section 8.2 Summary – pages 201 - 210
Interphase: A Busy Time
Interphase, the busiest phase of the cell cycle, is divided into three parts.
Interphase
DNA synthesis and replication
Centrioles replicate; cell prepares for division
Rapid growth and metabolic activity
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7. Section 8.2 Summary – pages 201 - 210
The Cell Cycle
Following interphase, a cell enters its period of nuclear division called mitosis.
Following mitosis, the cytoplasm divides, separating the two daughter cells.
Mitosis
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8. Section 8.2 Summary – pages 201 - 210
The Phases of Mitosis
The four phases of mitosis are prophase, metaphase, anaphase, and telophase.
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9. Section 8.2 Summary – pages 201 - 210
Prophase: The first phase of mitosis
During prophase, the chromatin coils to form visible chromosomes.
Spindle fibers
Disappearing nuclear envelope
Doubled chromosome
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10. Section 8.2 Summary – pages 201 - 210
Prophase: The first phase of mitosis
The two halves of the doubled structure are called sister chromatids.
Sister chromatids
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11. Section 8.2 Summary – pages 201 - 210
Prophase: The first phase of mitosis
Sister chromatids are held together by a structure called a centromere, which plays a role in chromosome movement during mitosis.
Centromere
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12. Section 8.2 Summary – pages 201 - 210
Metaphase: The second stage of mitosis
During metaphase, the chromosomes move to the equator of the spindle.
Centromere
Sister chromatids
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13. Section 8.2 Summary – pages 201 - 210
Anaphase: The third phase of mitosis
During anaphase, the centromeres split and the sister chromatids are pulled apart to opposite poles of the cell.
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14. Section 8.2 Summary – pages 201 - 210
Telophase: The fourth phase of mitosis
During telophase, two distinct daughter cells are formed. The cells separate as the cell cycle proceeds into the next interphase.
Nuclear envelope reappears
Two daughter cells are formed
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15. Section 8.2 Summary – pages 201 - 210
Cytokinesis
Following telophase, the cell’s cytoplasm divides in a process called cytokinesis.
Cytokinesis differs between plants and animals.
Toward the end of telophase in animal cells, the plasma membrane pinches in along the equator.
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16. Section 8.2 Summary – pages 201 - 210
Cytokinesis
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.
A cell membrane forms around each cell, and new cell walls form on each side of the cell plate until separation is complete.
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17. Section 8.2 Summary – pages 201 - 210
Results of Mitosis
When mitosis is complete, unicellular organisms remain as single cells.
In multicellular organisms, cell growth and reproduction result in groups of cells that work together as tissue to perform a specific function.
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18. Section 8.2 Summary – pages 201 - 210
Results of Mitosis
Tissues organize in various combinations to form organs that perform more complex roles within the organism.
Multiple organs that work together form an organ system.
Section 8.2 Summary – pages

19. Questions

20. Question 1
Question 1
The stringy structures in the cell nucleus that contain DNA are __________.
A. centromeres
B. chromosomes
C. genes
D. chlorophylls
Section 2 Check

21. Question 2
Look at the diagram and identify the stage of mitosis that is depicted.
Centromere
Sister chromatids
A. prophase
C. anaphase
B. metaphase
D. telophase
Section 2 Check

22. Question 3 What is the process by which a cell's cytoplasm divides?
A. cytokinesis
B. telekinesis
C. meiosis
D. mitosis
Section 2 Check

23. Question 4
In multicellular organisms, groups of cells that work together to perform a specific function are called __________.
A. organ systems
B. organs
C. tissues
D. cell cycles
Section 2 Check

24. Control of the Cell Cycle

25. Section 8.3 Summary – pages 211 - 213
Proteins and enzymes control the cell cycle
The cell cycle is controlled by proteins called cyclins and a set of enzymes that attach to the cyclin and become activated.
Occasionally, cells lose control of the cell cycle.
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26. Section 8.3 Summary – pages 211 - 213
Normal Control of the Cell Cycle
This uncontrolled dividing of cells can result from the failure to produce certain enzymes, the overproduction of enzymes, or the production of other enzymes at the wrong time.
Cancer is a malignant growth resulting from uncontrolled cell division.
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27. Section 8.3 Summary – pages 211 - 213
Cancer: A mistake in the Cell Cycle
Currently, scientists consider cancer to be a result of changes in one or more of the genes that produce substances that are involved in controlling the cell cycle.
Cancerous cells form masses of tissue called tumors that deprive normal cells of nutrients.
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28. Section 8.3 Summary – pages 211 - 213
Cancer: A mistake in the Cell Cycle
In later stages, cancer cells enter the circulatory system and spread throughout the body, a process called metastasis, forming new tumors that disrupt the function of organs, organ systems, and ultimately, the organism.
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29. Section 8.3 Summary – pages 211 - 213
The causes of cancer
The causes of cancer are difficult to pinpoint because both genetic and environmental factors are involved.
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30. Section 8.3 Summary – pages 211 - 213
The causes of cancer
Environmental factors, such as cigarette smoke, air and water pollution, and exposure to ultraviolet radiation from the sun, are all known to damage the genes that control the cell cycle.
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31. Section 8.3 Summary – pages 211 - 213
The causes of cancer
Cancer may also be caused by viral infections that damage the genes.
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32. Chapter 8 Questions

33. Question 3
Magnification of a plant cell reveals centromeres that have split and sister chromatids being pulled to opposite poles of the cell. This cell is in which phase of mitosis?
A. prophase
B. metaphase
C. anaphase
D. telophase
Chapter Assessment

34. Disappearing nuclear envelope
Question 4
Which phase of mitosis is depicted in this diagram?
Spindle Fibers
Doubled chromosome
Disappearing nuclear envelope
A. prophase
C. anaphase
B. metaphase
D. telophase
Chapter Assessment

35. Question 5
What is the term used for the period of the cell cycle represented by the red arrow in this graph?
A. prophase
DNA synthesis and replication
B. metaphase
Centrioles replicate; cell prepares for division
Rapid growth and metabolic activity
C. centrophase
D. interphase
Chapter Assessment

36. Question 6
What is the level of organization that is missing in this diagram?
Organ
Cell
Organ System
Organism ?
(muscle cell)
(stomach)
(digestive tissue)
(Florida Panther)
A. mass
C. tissue
B. cluster
D. cycle
Chapter Assessment

37. Question 7 Which structure represents a cell in prophase of mitosis?B C D
A. A
C. C
B. B
D. D
Chapter Assessment