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Name: Class: Date: # ___ Lab – The Cell Cycle in Onion Root Cells Purpose: To identify the phases of the cell cycle. Procedure: 1) Look at the phases of mitosis in the diagrams that follow. Note that the specimens have been stained so that we can see the chromosomes more clearly. Use them as references to identify the phases of mitosis on the picture of the onion root cell on page 3. Interphase Prophase Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html Page 1 of 6 Metaphase Anaphase Telophase After Cytokinesis Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html Page 2 of 6 2) Look at the picture of onion root cells on high power. Create a data table in the Data and Observations section below. Record the total number of cells in the picture. Record the number of cells observed in each part of the cell cycle: interphase, mitosis (all four parts), and cytokinesis. Include a column for the percentage of cells undergoing each part of the cell cycle. Note: It will be easier to count and keep track by following rows. (See diagram C on p. 215 of your text for a guide for counting.) Data and Observations: Onion Root Cells on High Power Data Table: Stage of mitosis Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Total number of cells Number of cells Percentage in each stage 100% Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html Page 3 of 6 Analyze and Conclude: 1) From the picture on page 3 of this lab sheet, what part of the cell cycle did you see most often? Why? 2) Where might you look for cells in the human body that are undergoing mitosis? 3) There are times when you will not be able to observe every phase of mitosis in a slide. Give one reason why this might be the case. PAGE 214 AND 215 FROM YOUR TEXT BOOK 4) Look at the diagram of the onion root tip on page 214 of your text. A) What part of the onion is area X? B) What part of the onion is area Y? 5) Observe Which area of the onion root tip (X or Y) had the greatest percentage of cells undergoing mitosis? The lowest? Use specific totals from your data table to support your answer. 6) Predict If mitosis is associated with rapid growth, where do you believe is the location of most rapid root growth, area X or Y? Explain your answer _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html Page 4 of 6 7) What factors might cause misleading results? How could you avoid these problems? ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ Make and use Graphs: Prepare a circle graph that shows the total number of cells counted in area X and percentage of cells in each phase of mitosis. Total number of cells per phase percentage of cells per phase Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html Page 5 of 6 YOUR DRAWINGS AS SEEN FROM THE MICROSCOPE (AT LEAST 8 DIAGRAMS- LABELLED) Sources: http://www.ndpteachers.org/perit/biology_image_gallery1.htm; http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html Page 6 of 6