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MITOSIS
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1.Where do Living things come from? “Living things are reproduced from other living things of the same kind”
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2. What is Spontaneous Generation?
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An INCORRECT theory that once said that living things could just appear from non-living things.
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3. Describe a “faulty” experiment that was used by early scientist to demonstrate this theory of spontaneous generation.
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a) Meat was left out for the “Air” to touch. b) A few days later, maggots appeared as if by magic on the meat.
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4. What was wrong with this spontaneous generation experiment?
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a) The controls were no good – The meat was left open, and anything could have gotten on it----- not just air!
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Pop’s note! What really happened? Flys landed on the meat and laid eggs.
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5. When did Francesco Redi try to prove that Spontaneous generation was a fake: 1668
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6. Explain the experiment performed by REDI:
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a) Redi placed a piece of meat in each of two jars.
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b) One jar was sealed with cheesecloth so that air could get in, but nothing else could.
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c) One jar he left open. Anything could get in.
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d) Flys got into the open jar, but not the sealed one.
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e) Maggots appeared on the meat in the open jar, but not on the meat in the sealed jar.
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7. What did redi’s experiment appear to prove?
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The maggots were the offspring of flys…not Produced by magic.
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8.Did Redi’s experiment totally disprove spontaneous generation? “For the moment, but not for long.”
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9. What caused the debate over spontaneous generation to start up again?
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In 1675, the world of microorganisms was discovered.
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10. Who finally ended the debate over spontaneous generation? “A french scientist named Louis Pasteur”
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11. What was Pasteur’s theory about microorganisms?
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Pasteur believed that Sleeping bacteria were riding on the dust particles in the air. When they landed on a food source, they became active!
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12. Describe Pasteur’s Experiment:
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a) Made a special flask with a “S” – shaped neck.
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b) Put broth in each one and boiled it.
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c) Microbes were killed in both flasks.
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d) He tilted the flask, so no bacteria could get in from the air.
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e) The broth stayed free of bacteria.
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f) He stood the flask up, allowing air to enter the neck of the flask, and soon bacteria began to grow in the broth.
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13. What did Pasteur prove?
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He proved that bacteria was indeed coming in from the air, not just appearing by magic.
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14. What is the theory of BIOGENESIS?
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“At the present time, and under present conditions on earth, all organisms are produced from other organisms of the same kind.
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15. What brought about the theory of biogenesis?
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The REDI experiments started it, then the pasteur experiments proved it.
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16. What role did Virchow play in the development of the cell theory and in the theory of biogenisis?
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In 1858, Virchow, a Russian pathologist, observed cells dividing. This proved that cells come from other cells.
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Reproduction Of Body cells
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17. What is a SOMATE cell?
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Any body cell that is not a SPERM or an EGG.
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18. Why would an organism need to reproduce somate cells?
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1- GROWTH
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2- BODY REPAIR
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19. Differentiate the parent cell and the daughter cells:
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The parent cell has enlarged and prepared itself to divide.
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The daughter cells are the two cells that result from cell division.
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20. Why is it better to create many tiny cells instead of just making a few big cells?
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The smaller the cell, the easier it is for the cell to maintain itself, like getting food and getting rid of waste.
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21. What is the cell cycle?
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A twenty hour series of events that a cell goes through in order to become a parent and then to divide.
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22. Explain what happens at each step of the cell cycle:
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a)mitosis: The parent cell divides into 2 daughter cells. Takes 2 hrs.
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b)G1 phase Daughter cells get much bigger, and develop more cytoplasm Takes 4 hrs.
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c) S phase: Cell duplicates its chromosomes Takes 10 hrs
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d) G2 The cell creates extra organelles Takes 4 hrs Cell enters mitosis again.
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23. What is the difference between interphase and mitosis itself?
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Interphase is when the small daughter cells prepare to become a parent. Mitosis is when the parent divides itself into 2 daughter cells.
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24. What is Chromatin?
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Thin strands of DNA found locked away in the nucleus of a cell.
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25. Explain how and when a chromatin strand becomes a chromosome:
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How? The chromatin is rolled up on a protein spool called a HISTONE.
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When? During the S-phase of interphase
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26. Explain how and when a chromosome becomes a pair of sister chromatids:
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How? Each chromosome is duplicated! The matching pair is called “Sister Chromatids”
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When? During the S-phase of interphase
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27. Draw, label, and color a picture of the sister chromatids that we find going into prophase:
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28. Outline the steps of mitosis:
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http://www.johnkyrk.com/mi tosis.html
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Prophase 1- Nuclear membrane dissolves.
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Prophase 2- Nucleolus dissolves
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Prophase 3- Centrioles appear
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Prophase.4- Sister chromatids Are thick and visible.
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Metaphase 1- Centrioles move to North and south poles.
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Metaphase 2- Chromosome pairs Line up in the middle of the cell.
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Metaphase 3- Centrioles send down spindle fibers which attach to the centromeres of the sister chromatids.
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Anaphase 1- Chromosome Pairs separate!
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Anaphase 2- Spindle fibers pull the separated chromosomes towards the poles.
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Telophase 1- Chromosomes reach the poles
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Telophase 2- Cell membrane begins to indent and cytoplasm begins to separate.
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Telophase 3- Complete separation has occurred!
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Telophase 4- New nuclear membrane will form, and nucleolus will reform.
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Telophase 5- The two new daughter cells will enter INTERPHASE
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29. WHAT IS MEANT BY THE RATE OF CELL DIVISION?
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“How fast and how often specific cells reproduce themselves”
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30. How often do the following healthy cells reproduce themselves?
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Blood cells? Every hour
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Liver cells? Only as needed
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Skeletal Muscle? When torn or injured
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.Nerve cells? Never. It remains in interphase indefinitely.
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.Smooth Muscle like stomach muscle? Never. It stays in interphase indefinitely.
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31. Explain how the rate of mitosis is associated with the following conditions:
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Old Age: Mitosis slows down and eventually stops. The cells we have are not replaced, just allowed to wear out.
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Cancer The speed of mitosis is too fast! The cells do not function and begin to build up into piles called TUMORS.
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32. Explain what has happened genetically to the people in the following pictures:
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? Before After
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BeforeAfter ?
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Their rate of mitosis has slowed down to the point that they are no longer replacing their body cells. Old cells are wearing out.
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My little Mitosis Book
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PROPHASE
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1- Nuclear membrane dissolves 2-Nucleolus dissolves
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