Ex ~ Modeling the Phases of the Cell Cycle

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					                      Class Set ~ Please Return

                   Ex ~ Modeling the Phases of the Cell Cycle
Introduction: In a growing root, the cells at the tip of the root are constantly dividing. Because each
               cell divides independently of the others, a root tip contains many cells at different
               phases of the cell cycle. This makes a root tip an excellent tissue in which to study
               the cell cycle. In this investigation, you will identify and describe the phases of the cell
               cycle in root tip cells.

Problem: What do the phases of the cell cycle look like in a typical plant cell? And, how much time
          do cells spend in each phase of the cell cycle?

Procedure ~ Part A - The Cell Cycle
1. Copy the Analysis - Plant Cell (Onion Root Tip) on                Analysis - Plant Cell                  Name ______________
   a piece of paper.                                                                                        period ____ date _____

2. Observe the boxlike cells that are arranged in rows
   on your onion root tip slide (x400). Scan across
   one row and down to the next row and compare
   the cells. The genetic material, nucleus or
   chromosomes, in the cells has been stained to                      Stage: Interphase   Stage: Prophase      Stage: Metaphase
                                                                      Description:        Description:         Description:
   make it easily visible.
3. Locate a cell in interphase. Sketch this cell on your
   Analysis Paper, label the cell (interphase) and
   write a description of what is occurring in the cell at
   this phase of the cell cycle.
4. Repeat step 2 for prophase, metaphase,
   anaphase and telophase.
                                                                                 Stage: Anaphase      Stage: Telophase
Procedure ~ Part B - How Much Time Do Cells                             Description: Description:

Spend in Each Phase
1. Copy Table 1: Observations on a piece of paper.
2. Looking at the picture of an onion root tip slide,
   determine what phase each cell that is marked with
   an “X” is in. RECORD this observation with a tally
   mark in the data table.
3. Count your tally marks and determine the total number of cells counted for each phase. RECORD.
4. Determine the total number of cells observed. RECORD.
5. Determine the Percentage of cells that are in each phase. See calculation on the next page. Your
   answers should be accurate to 3 decimal places.
6. Determine the approximate duration (Time in minutes) of each phase in the growing onion root tip.
   The average time for onion root tip cells to complete the cell cycle is 24 hours, or 1440 minutes.
   Use the data you collected from this slide to calculate the time in minutes for each phase of the cell
   cycle in a 24 hour period. See calculation on the next page. Your answers should be rounded to
   the nearest whole number.




Biology ~ Ex - Modeling the Phases of the Cell Cycle ~ page 1 of 1
                      Class Set ~ Please Return

                                 Copy the following table on your lab paper.
Table 1: Observations
        Phase               Tally Marks          Number of Cells     Percentage           Time
                                                                                       in minutes

     Interphase

     Prophase

     Metaphase

     Anaphase

     Telophase

            Total Number of Cells ----->


Calculations: Copy each calculation on your paper and then solve using your data. Remember to
put the percentage and minute for each phase in your data table.

Interphase: 
# cells in interphase / total cells = ______ x 1440 min = _________ minutes

     
      
       
       
     

Prophase: 
 # cells in interphase / total cells = ______ x 1440 min = _________ minutes

Metaphase: # cells in interphase / total cells = ______ x 1440 min = _________ minutes

Anaphase: 
# cells in interphase / total cells = ______ x 1440 min = _________ minutes

Telophase: 
# cells in interphase / total cells = ______ x 1440 min = _________ minutes


Analyze and Conclude: All responses should be in complete sentences.
1. Refer to the percentage of total cells counted in each phase on your data table. Sketch a pie graph
   of the percentages of cells in each phase of the cell cycle. Be sure to include a title and a key for
   your graph.
2. What is the relationship between the processes of mitosis and cytokinesis?
3. Describe how cytokinesis different in plant and animal cells.
4. In what phase of the cell cycle is the genetic information replicated.
5. In what phase of the cell cycle is the contents of the nucleus divided?
6. What would result in the daughter cells if the genetic information was not replicated prior to the
   nucleus dividing?


Biology ~ Ex - Modeling the Phases of the Cell Cycle ~ page 2 of 1