06 Mitosis Onion Root Tip Lab revision 2011 by py6lGT


									Biology                                                                         Name ___________________________
Mitosis within an Onion Root                                                    Period ____ Date ________________

The cell cycle, regulated by cyclins (proteins), carefully controls the growth and division of cells. Plants are frequently
used to study cell division, particularly cells within roots, as they continue to grow in an attempt to locate nutrients and
water for the plant. At any given time, you can find cells in various stages of mitosis, thus studying this process as an
ongoing, continuous, cyclic event in living organisms.
A thin slice of an Onion Root tip will be used in this lab. It has been wet mounted onto a slide, stained with methylene
blue so the chromosomes would be visible, and sealed with a cover slip. Since cells carry out their own cell cycle
individually, you will see cells at various stages within the same onion root.

1. Title - _________________ (come with a name for this lab)

2. Problem (Write this as a question) ______________________________________________________

3. Hypothesis – (Use an “If…then” statement) ______________________________________________

4. Equipment -
                             Microscope   prepared slide of an onion root tip               calculator

5. Procedure
    a. Draw sketches of Interphase and the four phases of Mitosis in the Data Table below.
    b. Properly use the microscope:
        1. Plug in the microscope & turn on the light
        2. Begin with the low power (4x) objective in place
        3. Focus using the coarse adjustment knob, then the Fine knob
        4. Place the slide on the stage
        5. Adjust the light by opening or closing the diaphragm and the sliding light intensity dial.
        6. Find the root tip under low power, move to medium (focus)
        7. Move to High Power (now be sure to only use the fine adjustment knob for focusing)
        8. Your task is to count and identify all cells in your view finder (the circular field of view you see as
           you look into the microscope)
        9. Document the number of cells you find in each of the five phases: interphase, prophase, metaphase,
           anaphase, and telophase.
        * 10. Be sure to devise some technique for viewing all the cells of the specimen provided (i.e. starting at
           the top left corner – looking down the column of cells then back up to the top, moving across the
           view of view until you have identified each cell.)
        * Note: you may have to use the fine focus knob to adjust the view of the cells as you go along.
        11. Then you will count up the number of total cells
        12. Next, determine the percentage of cells in the different stages of cell division by taking the number
           of cells in that stage and dividing it by the number of total cells then multiple it by 100 to get the
           percentage. This percentage should allow you to predict how much time a              dividing onion root
           cell spends in each phase.
                                                                # of cells in phase x 100
                                                                     Total Cells

Mitosis Onion Root Tip Lab                                   L.More                                          Olympian High School
          13. Base your total cell cycle on 24 hours, meaning if it takes one day (24 hours) for an onion root cell to
                 go through its cell cycle, how long would it be in each stage?              24 x #%

Mitosis Onion Root Tip Lab                               L.More                                      Olympian High School
6. Data:
                              Interphas     Prophase      Metaphase Anaphase              Telophase      Cytokinesis            Total

     Draw plant
     cells in these
       of cells
     Percentage                                                                                                             Predict 100%
       of cells
  # of cells in phase x 100                                                                                               Actual = ____%
         Total Cells
     (Show your work)

    Time in stage                                                                                                          Predict 24 Hrs
         24 x #%
     (Show your work)
     Hours and Minutes                                                                                                          Actual

     .## x 60 = minutes       __ __:__ __   __ __:__ __    __ __:__ __      __ __:__ __    __ __:__ __    __ __:__ __         __ __:__ __
     (Show your work)

7. Questions
       a. Using the skill of Analysis here requires that you systematically examine aspects of the cell cycle.
          1. (Identifing it’s parts) List the parts of the cell cycle in sequence. ___________________________
          2. (Relationship of the parts) Determine the role the various phases play for the cell cycle:
               1. Interphase ________________________________________________________
               2. Mitosis ___________________________________________________________
               3. Cytokinesis _______________________________________________________
          3. (Relationship to the whole) What is the significance of the cell cycle to the preservation of an
               organism? __________________________________________________________________
       b. The skill of Evaluation involves the ability to judge results based on a defined criteria.Use the data
           you obtained in the lab to create a Pie Chart depicting the percentage of cells or time cells spent in
           Interphase, Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis, then compare your pie
           chart to the pie chart scientists have created based on their research and experimentation.
 Pie Chart with My Data             1. Compare your times to that of the scientists’ times:                       Scientists’ Pie Chart
                                        a. Interphase (mine) _____ vs (scientist’s) 19:24
                                        b. Prophase (mine) ______ vs (scientist’s) 1:28
                                        c. Metaphase (mine) _____ vs (scientist’s) 0:48
                                        d. Anaphase (mine) _____ vs (scientist’s) 0:43
                                        e. Telophase (mine) _____ vs (scientist’s) 0:43
                                        f. Cytokinesis (mine) ____ vs (scientist’s) 0:52
                                     2. Which phase does a cell spend most of its time? _______
                                     3. Do your numbers show that? ___
Mitosis Onion Root Tip Lab                                         L.More                                               Olympian High School
8. Conclusion (remember, there should be three separate paragraphs)

          a. Restating your hypothesis (talk about it in the past tense now that the lab is done – what did you do
                  and what actually happened?) as you discuss its accuracy, be sure to reference to your specific
                  data findings.

          b. What are possible sources of errors one may encounter in the lab? And why would they pose a
                problem? (Be sure to list at least 3) Make a chart, clearly stating the error and its effect.

    Note: If your pie chart does not match the scientists’ pie chart, be sure to give possible explanations here.

                             Possible Source (cause) of Error          Specific effect that error would have




                    Please do NOT say if someone does not follow the instructions – that is too vague. Be specific.

          c. Apply & relate – personalize this, make it real for you. Give accounts in your own life where mitosis
                 and the cell cycle are busy at work, and why it’s important. (Give at least three examples).

                    To ensure you are relating the concepts of this lab to your own life, please use I, Me, My
                    statements, and do not say if I were a scientist or if I ever did this lab again.

            Use this sentence starter: “There are many examples in my own life were mitosis plays a critical role,
                         three such examples are…”

If absent: use online lab to fill in chart: www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html

Mitosis Onion Root Tip Lab                                  L.More                                    Olympian High School

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