Biology 100 CellLaboratory
For cells that divide by mitosis there are three major parts of the cell cycle: interphase, mitosis, and cytokinesis. Review these major parts and answer the following questions so you are familiar with the major stages before beginning the laboratory.
Multicellular organisms grow by making more cells. A cell undergoing its cell cycle and mitosis results in two identical daughter cells. In plants special growth areas called meristems are typically found at the tips of roots and stems. In animals, growth is usually not relegated to a specific area of the organism.
For this lab we will be using prepared onion root tip slides to study plant mitosis and calculate the relative duration of the stages of mitosis. The cell cycle for actively dividing onion root tips is approximately 24 hours. Since these cells are not living, we will estimate the time each cell spends in each stage based on what percentage of the cells are in each phase.
Mitosis is divided into the following stages: prophase, metaphase, anaphase, and telophase. Match each stage with the major action taking place in the cell and then review the photos of onion root cells in Interphase and different stages of mitosis.
Match by drawing a line from the stage to the correct description of the cell activity:
|Interphase||Nuclear envelope reforms|
|Prophase of mitosis||DNA is duplicated|
|Metaphase of mitosis||Sister chromatid separate and move to opposite poles|
|Anaphase of mitosis||DNA condenses into visible chromosomes|
|Telophase of mitosis||Chromosomes align along the middle of the cell|
Credit: © Carolina Biological/Visuals Unlimited
Onion root tip mitosis – Interphase stage.
Credit: © Carolina Biological/Visuals Unlimited Onion root tip mitosis – Metaphase stage.
Credit: © Carolina Biological/Visuals Unlimited Onion root tip mitosis – Early anaphase stage.
Credit: © Carolina Biological/Visuals Unlimited Onion root tip mitosis – Late anaphase stage.
Credit: © Carolina Biological/Visuals Unlimited Onion root tip mitosis – Telophase stage.
Does a cell spend equal amounts of time in each of the stages of the cell cycle?
Remember, a hypothesis is a tentative and testable explanation for an observation or answer to a question. In the space below describe your hypothesis or hypotheses and the reasoning behind why you expect that cells will or will not spend equal amounts of time in each of the major stages of the cell cycle (interphase, prophase, metaphase, anaphase, and telophase).
Your lab report for the Cell Cycle Lab should include the following headings:
Images from prepared mitosis microscope slides
|Number of Cells||Percent of Total Cells Counted||Time in minutes for Each Stage|
|Field 1||Field 2||Field 3||Total|
|Total Cells Counted|
To determine the percent of total cells counted for each stage use the following formula:
(Total cells counted in each stage / Total cell counted) X 100
For example: if a total of 5 cells were counted in telophase and the total of all cells counted was 322, then the percent of total cells counted in telophase would be 5/322 = 0.015 X 100 = 1.5% To determine the minutes of the cell cycle spent in each stage use the following formula:
Percentage of cells in stage X 1,440 minutes For example: 1.5% X 1440 = 21.6 minutes