Interphase and Mitosis Inquiry by 2mz1O10

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									Interphase and Mitosis Inquiry                                Name(s):
Introduction:
      The cell cycle consists of a growth period called interphase followed by a round of division called mitosis.
During interphase the cell grows, DNA is replicated, and organelles are manufactured. Mitosis, which occurs in 4 phases,
is the division of nuclear material between two cells so that each new cell is identical to the original cell. Daughter cells
obtain the same number and type of chromosomes as the parent cell because the DNA is replicated during interphase.
Different types of cells go through the cell cycle at different rates, depending on the amount of time needed to complete
interphase, whereas mitosis typically takes an hour. The root tips you will observe represent a ‘snap shot’ in time,
meaning these cells have been captured in certain stages of the cell cycle. While you are completing the lab, pay attention
to the relative number of times you can find each phase. Meaning, note and rank the phase(s) you see most often to least
often.
Purpose: To locate cells in prepared slides that represent phases of the cell cycle.
Materials: microscope, mitosis slides (onion root tip), computer, pen/pencil
                                                                                                       Onion Root Tip
Procedure:
1. Under LOW power, locate a region of rapidly dividing cells on a prepared onion root
    tip slide (see red box, fig. 1). This region is toward the bottom of the rounded end
    of the root tip. DO NOT MOVE THE STAGE, but move the nosepiece to HIGH power.
2. Using your notes and pictures, identify a cell in interphase on the slide.
3. When you have found interphase, have all of your partners check the cell you have
    identified. Once you all agree, raise your hand to have your teacher verify your
    accuracy for that stage. You have 2 chances to correctly identify each stage, so
    be sure you all agree before you have your teacher verify the phase you identify.
4. While you patiently wait for the instructor, your group should answer the
   questions related to interphase (or the phase you happen to be working on).
5. Be sure to have your teacher verify your accuracy with their initials on a
   hard copy or a verification code typed next to the phase. Save ‘ctrl S’.
6. Follow steps 2 - 5 for prophase, metaphase, anaphase, telophase, and daughter cells.
   TO SAVE TIME, YOU CAN IDENTIFY THE PHASES IN ANY ORDER.
7. Be sure to answer the analysis questions at the end.
8. If you need to, you can use the ‘arrow tool’ to drag and resize the images to see details.
Results:
I. Interphase __
                       a. Name the contents of the nucleus during interphase.
                          **
                       b. Are a nucleolus and nuclear membrane present?
                          **
                       c. Are distinct rod, shaped structures called chromosomes easily observed?
                          **
                       e. What term is used to describe nuclear contents during this phase?
                          **
                       f. What important event occurs to genetic material during interphase?
                          **
                       g. In general, what other important events occur during interphase?
                          **
                       h. Interphase used to be referred to as a resting phase of the cell cycle. Why might this be
                          an inappropriate description of interphase?
                          **
                       i. Scan the field of view in your microscope and rank interphase according to the relative
                          number of times it can be found compared to the other phases.
                       (5 = most found, 4 = frequently found, 3 = occasionally found, 2 = rarely found, 1 = very rarely found)
                          **
II. Prophase __
                    a. Are chromosomes visible now?
                       **
                    b. Describe the changes that have occurred to the nucleolus and nuclear membrane.
                       **
                    c. Explain why chromosomes can now be observed but not during interphase.
                       **
                    d. Scan the field of view in your microscope and rank prophase according to the relative
                       number of times it can be found compared to the other phases.
                    (5 = most found, 4 = frequently found, 3 = occasionally found, 2 = rarely found, 1 = very rarely found)
                       **
III. Metaphase __
                    a. Describe where the chromosomes are located in relation to the cell.
                       **
                    b. Is there evidence of chromosome duplication (replication)? EXPLAIN.
                       **
                    c. What are the fibers called that become visible during this phase?
                       **
                    d. Where does a spindle fiber attach to on a chromosome?
                       **
                    e. Scan the field of view in your microscope and rank metaphase according to the relative
                       number of times it can be found compared to the other phases.
                    (5 = most found, 4 = frequently found, 3 = occasionally found, 2 = rarely found, 1 = very rarely found)
                       **
IV. Anaphase __
                    a. In metaphase, chromosome pairs were lined up along the cell’s center. Describe what is
                       occurring to each chromosome pair during anaphase.
                       **
                    b. Toward what area of the cell are the chromosomes being pulled or directed?
                       **
                    c. What structures are responsible for the movement of chromosomes? How do they work?
                       **
                    d. Scan the field of view in your microscope and rank anaphase according to the relative
                       number of times it can be found compared to the other phases.
                    (5 = most found, 4 = frequently found, 3 = occasionally found, 2 = rarely found, 1 = very rarely found)
                       **
V. Telophase __
                    a. What cell parts begin to reappear during this phase?
                       **
                    b. Describe the location of the chromosomes now compared to during metaphase.
                       **
                    c. Cytokinesis occurs during telophase. How can you tell when it is occurring in a plant
                       cell? **
                    d. How can you tell when cytokinesis is occurring in an animal cell?
                       **
                    e. Scan the field of view in your microscope and rank telophase according to the relative
                       number of times it can be found compared to the other phases.
                    (5 = most found, 4 = frequently found, 3 = occasionally found, 2 = rarely found, 1 = very rarely found)
                       **
VI. Daughter Cells __
                            a. How many cells have now been formed from the original cell?
                               **
                            b. How does the number of chromosomes in each daughter cell compare to the original
                               cell? (HINT: read the introduction again!)
                               **
                            c. What phase of the cell cycle will daughter cells enter?
                               **

Analysis:
1. The term ‘mitosis’ comes from a Greek word mitos meaning ‘thread.’ Why is this word helpful in describing
   nuclear division?
   **
2. Explain how mitosis helps organisms grow.
   **
3. List in order (highest to lowest) the rankings you assigned each phase?
   **
4. According to the data you ranked or collected, what stage represents the longest phase of the cell cycle?
   **
5. According to the data you ranked or collected, what stage represents the longest phase of mitosis?
   **
6. Assume that you recorded the following data when you looked at your root tips. Out of 250 cells, imagine
   that you observed a certain number of cells in each phase of the cell cycle. Your mission is to determine the
   fraction of cells in each phase, the percentage of time a cell spends in each phase, and the number of degrees
   each phase would represent in a pie graph.

                                 Interphase     Prophase     Metaphase      Anaphase       Telophase     TOTAL
  a. number of cells in              186           36           13             5               10         250
     this phase
  b. fraction of cells in                                                                                    1.0
     this phase
  c. % of time cell                                                                                       100%
     spends in phase
  d. # of degrees in a                                                                                         ◦
                                                                                                           360
     pie graph

7. Insert a pie chart below, that accurately represents your calculations for row d. from the table above.
                                            *> Insert Pie Chart Here <*

8. Assume that cells in an onion root tip require 12 hours to complete the cell cycle. Use the percentages you
   have determined above to calculate the amount of time each phase takes.
   Interphase **
   Prophase **
   Metaphase **
   Anaphase **
   Telophase **

								
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