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Mitosis Onion Root Tip Lab

November 29, 2011 by mpozo · 1 Comment · Uncategorized


Mitosis is the process by which a single cell divides into two identical “daugter” cells, each with an identical number or chromosomes as the parent cell.  The four stages of mitosis follow each other without interruption, and take place in all living cells.


In this lab, you will examine cells from onion root tissue.  Root-tips are regions of active cell division.  It is very likely to observe every stage of cell division in root tips.  You will examine onion root cells under the microscope and identify the different stages of cell division in the tissue sample.  You will also determine how much time is spent in each stage of the cell cycle.


To review the cycle of Mitosis, please visit Arizona Biology’s website.


Lab Question:

How much time do cells spend in each part of the cell cycle?

interphase- 45%     prophase-10.5%     metaphase- 6%     anaphase- 12.5%     telophase- 25%


  1. Obtain a slide of onion root cells.  Examine the slide under the microscope using the low-power lens.
  2. Find examples of cells in each stage of the cell cycle, including interphase and the stages of mitosis.  Draw and label each cell in the provided table.  Label structures within the cell on Table 1 of the handout (paper).
  3. Select a random area of the slide to study using the high-power lens; focus on high power.
  4. Identify the stage of each cell in the view, and record your data in Table 2.
  5. Repeat steps 3 & 4 two more times for different areas of the slide.
  6. Calculate the percentage of cells in each part of the cell cycle for each sample.  Complete Table 2.
  1. Sample Calculation: In the whole cell cycle there were around the same amount of cells in the two spots we looked at, however Interphase had the most amount of cells both times. There were 25 and 29 cells in each interphase check, 33 and 7 for prophase, 3 and 4 for metaphase, 4 and 8 for anaphase, and 10 and 16 for telophase. At the end there were 64 cells in the first round and 65 cells in the second round. For interphase the first round had 39% all cells, 34%prophase, 4.6% for metaphase, 6% for anaphase and 15% for telophase. For the second round interphase had 45% all cells, 10.9% prophase, 6% metaphase, 12.5% anaphase, and 25% telophase


Create a blog post on Edublogs called “Mitosis Onion Root Tip Lab” with the following tags: Mitosis, Onion Root Tip, Interphase.  Copy and paste the questions below the solid line and answer in your post.

  1. What patterns exist in your data?  In which stage of the cell cycle are most of the cells you examined?  How does this data support what you know about the cell cycle?  INTERPHASE WAS ALWAYS THE STAGE IN THE CELL CYCLE WITH THE MOST CELLS COMPARED TO THE OTHER STAGES IN THIS EXPERIMENT
  2. Find the average percentage of cells in each stage of the cell cycle among the three samples.  Assume that a cell takes 24 hours to complete one cell cycle.  Calculate how much time is spent in each stage of the cell cycle.  (Hint: Multiply the percentage of cells in each stage, as a decimal, by 24 hours).        ?
  3. The cells in the root of an onion are actively dividing.  How might the numbers you count here be different than if you had examined cells from a different part of the plant?     IT WOULD BE ABOUT THE SAME AMOUNT OF CELLS BUT DIFFERENT AMOUNT OF DIFFERENT STAGES OF CELL CYCLE
  4. Using the data from Table 2, create a graph in Google Spreadsheets using the % of cells in each stage of Mitosis.  Add a title and label the graph.  Upload a picture of the graph to your post.
  5. A chemical company is testing a new product that it believes will increase the growth rate of food plants.  Suppose you are able to view the slides of onion root tips that have been treated with the product.  If the product is successful, how might the slides look different from the slides you viewed in this lab? MIGHT HAVE LESS OF THE STAGES BECAUSE THEY WILL BE PRODUCED IN FACTORIES
  6. Design an experiment that would test the product described in question 4.  Assume the product is a liquid that can be added to the soil in which the plant is growing.

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One Comment so far ↓

  • drott22

    DC: #2 take the % of each cell stage and multiply by 24 to give the proportion of cells in each stage for a 24 hour cycle; should be more cells in interphase; 4

    AS: 1; not complete

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