Cell Cycle Lab
How long do the stages of the cell cycle take?
The purpose of this lab is to estimate how long each stage of the cell cycle is. Cells from the tips of onion
(allium) roots will be observed. The tip of roots is where the root ___________ and gets longer as it is
tapping into water sources. Thus it is an area where cells are reproducing and dividing. The most
important part of the cell cycle is making sure the new cell gets a copy of the DNA.
Remember the different stages of the cell cycle. _____________ is where the cell does normal cell
functions. It ___________, _________________ its DNA and gets ready for cell ____________. The
next stage is ___________. Mitosis consists of 4 stages. ___________ is where the DNA coils up to
form ______________ and the nuclear membrane breaks down. ________________ is when the
chromosomes line up at the center of the cell. ______________ is when the chromosomes get pulled by
the spindle fibers to the opposite sides of the cells. _________________ is when a new nucleus forms
around each set of chromosomes. After mitosis ____________ happens and the cell membrane halves
to form 2 new cells.
1. Each group gets a slide that contains 3 onion root tips.
2. Look at the slide on low power first. Select one of the onion root tips. Make sure it is aligned in
the middle of the view circle.
3. Eventually focus on medium and then high power. The diaphragm might need to be set on 4 or 5
so the cells appear darker.
4. On high power, examine the cells row by row. Count the cells that are in interphase. Record that
number in the data table under first sample.
5. Repeat step 4, this time count the cells that are in prophase, metaphase, anaphase, and
6. The second person in the lab group repeat steps 2-5 this time enter into the data table under
7. The third person in the lab group repeats steps 2-5 this time enter into the data table under the
8. Everyone in the group is responsible for putting the microscope away properly and returning the
Data, Calculations, and Graph
st nd rd
Stage of Cell Cycle 1 sample 2 sample 3 sample Total number
Total number of cells counted
Calculate the average (mean) number of cells for each stage. Then calculate the percent for each stage.
Label and show your work below.
Make a pie chart out of the percent for each stage. Make sure you label each section of the pie chart.
1. Which stage of the cell cycle did you observe most often?
2. The cell cycle for onion root tips takes about 720 minutes (12 hours). Use your data and the
formula below to find the number of minutes each stage takes.
Time for each stage = % for each stage x 720 min.
3. Use the data to compare the amount of time spent in mitosis with the total time for the whole cell
cycle (mitosis and interphase).