Mitosis in an Onion Root
Introduction: Mitosis can be observed in cells that are in a state of growth fairly easily. In this lab, you will observe cells and identify which stage of cell division the cells are in. Remember, interphase is not technically a part of Mitosis, but it is a part of the cell cycle and many of the cells you view will be in interphase.
Learning Target: I can describe, diagram, and identify the stages of mitosis.
Review of Prior Knowledge: In the following chart, list the distinguishing characteristics of each stage of Mitosis (including interphase) using your own words:
Distinguishing Characteristics (Major Happenings)
Interphase
Prophase
Metaphase
Anaphase
Telophase
*You may consult your lab partner if you do not remember any information, but still answer in your own words.
Procedure: You will be given a slide of onion root tip. Growth occurs when cells divide, so the root tips should have several cells in the process of cell division at all times. View the root tip under the microscope on high power, and search for an organized block of cells where nuclei are plainly visible and various phases are seen. Remember, most activity is near the tip of the root! Once you have located a good field of view, ensure you are on high power, and DO NOT MOVE YOUR SLIDE FOR THE REST OF ACTIVITY. You need to count the number of cells you see in each stage of the cell cycle, and fill in the table on the next page:
Stage:
Estimated Number of Cells in the viewing field in this phase (400x):
Sketch of a Cell in this phase:
Interphase
Prophase
Metaphase
Anaphase
Telophase
Analysis Questions:
Why is the onion root a good specimen for studying mitosis?
Most of the cells in your field of view that you chose were in which stage of the cell cycle, interphase or cell division? _______________________ Does this support what you know about timing of the cell cycle? ____________ Why or why not?______________________________________________________
______________________________________________________________________________________
Sketch one cell in either metaphase or anaphase. Be sure to show the spindle fibers and centrioles (even though you may not see the on your slide), and LABEL the cell membrane, cytoplasm, sister chromatids or chromosomes, centromere, spindle fibers and centrioles.
Which phase of mitosis is the easiest (in your opinion) to see on the slide? ________________________
What makes it easy to identify? ___________________________________________________________
_____________________________________________________________________________________
*You are expected to be able to focus a microscope on high power and identify all of the phases of mitosis on an onion root OR fish bastula slide*
