The Edward and Bella Lab

Mitosis in Onion Root Cells Essential Question: Where does mitosis occur in onion root tips? Are all cells undergoing this process at the same time?

Hypothesis: After you complete the lab make a hypothesis and fill it into this space  Procedure: Place the prepared slide on the stage of the microscope, and focus with low power objective. Scan the onion root tip for a region in which cells are in various mitotic phases. Once you have identified a region, switch to high power. Find a cell that is in one of the mitotic phases. Draw the cell you are observing, and label its phase. Use the handout on the lab station to make this identification. Repeat step 3. Try to find cells in each of the mitotic phases. Switch back to low power. In one region of the root tip, count the number of cells in different mitotic phases. In the same region, count the number of cells that are not undergoing mitosis. Record these numbers. Repeat step 5 for three different regions of the root tip. Show which regions you counted. Draw a simple sketch of the root tip, and shade in the areas you observed.

Data: Prepare a data table appropriate to this lab. Remember: you are counting numbers of cells found in various stages of mitosis. There are 5 stages of cell division. You are going to make different rounds of observations. Do the math, make the appropriate number of rows/columns.

Analysis/Results: Answer each of the following questions: Are cells undergoing mitosis in every part of the onion root tip? Were all of the mitotic cells in the same phase of mitosis? Is the number of cells undergoing mitosis the same in every region of the onion root tip? In which regions of the root tip were the greatest number of mitotic cells? In which regions were the fewest mitotic cells? For each of the four regions you observed, calculate the percentage of mitotic cells compared to the total number of cells (hint: divide your visual area into quadrants (4’s) and then count the number of cells you see in each quadrant. Divide the number of cells in some stage of mitosis by the total number of cells in the quadrant and you will get the percent).

Conclusion: How would you explain the pattern of the occurrence of mitosis? Why would the root have such a pattern? Write a paragraph stating your conclusion with your observations.

Sample Data Table Interphase Prophase Metaphase Anaphase Telophase Quadrant 1 Quadrant 2 Quadrant 3 Quadrant 4