Name _________________________________
Due Date _______________
Period ________
PAP Biology SAC Lab
Biology I, MISD
Skills
Objectives
5A) describe the stages of the cell cycle,
including DNA replication and mitosis
5D) recognize that disruptions of the cell cycle
lead to diseases such as cancer.

Calculate percentage

Properly use a microscope

Correctly draw cells in cell division using the
rules of scientific drawing
Onion Root Tip Lab
Prelab Assignment:
1. What phase in the cell cycle is right before mitosis? ______________________
2. What are the four stages of mitosis, in order? _________________________,
________________________, _______________________, _______________________
3. What phase in the cell cycle directly follows mitosis that divides the cytoplasm into 2 new cells?
______________________________
4. What are the 2 differences between plant cell division and animal cell division?
1. Animals cells have organelles that help create the spindle during cell division that are known as
_________________________ while plant cells do not.
2. Plant cells form a ______________ _______________________ that becomes the cell wall between the
2 new cells while animal cells form a _____________________ ______________________ that splits
the cell into 2 new cells.
Questions 5-9: Use the diagram above to complete the table below. Identify the phase of the cell cycle that each cell in
the diagram is in and write the number(s) of those cells in the table.
Phase in the Cell Cycle
Numbers of the Cells
Interphase
Prophase of mitosis
Metaphase of mitosis
Anaphase of mitosis
Telophase of mitosis
Skills
Total Number of Cells
9
2
3
2
2
Applications
Concepts
pg. 1
Name _________________________________
Due Date _______________
Period ________
Background:
In order to grow or repair damage, organisms need to undergo a process called cell division. Cell division includes
three main parts—interphase, mitosis, and cytokinesis. The cell spends 90% of its time in interphase, during which the
cell is busy performing the jobs it was designed to do. Also during interphase, the cell replicates its DNA to get ready for
mitosis.
During mitosis there are four phases—prophase, metaphase, anaphase and telophase. These four phases involve
dividing the nucleus and separating its chromosomes. Cytokinesis immediately follows mitosis and involves the formation
of a cell plate (in plant cells) or a cleavage furrow (in animal cells) to create two new identical daughter cells from the
original cell.
In this lab, you will look at the cells located in the tip of an onion root (the genus of this plant is Allium, which is
printed on the slides). In plants, such as the onion, its roots are continually growing in search of food and nutrients.
Because of this continuous growth, it is easier to see the many different stages of cell division occurring in one region.
The pictures and slides you will look at are thinly sliced portions of an onion root and have been stained in order to see
the chromosomes better.
Purpose:
The purpose of this lab is to identify cells in the various stages of cell division when looking
through a microscope, as well as to determine the relative amount of time spent in each stage of the
cell cycle by calculating percentages.
Hypothesis:
If there are more cells in interphase in a tissue sample than in any other phase of the cell
cycle, then that tissue spends the most time in ____________________________.
Materials:

5 colored pencils/hi-liters: yellow, pink or red, blue,
orange & green


“Cells in various stages of cell division” hand out
microscope



ruler
calculator
prepared slide of an onion root tip (Allium)
Safety:


Follow all microscope safety rules and proper use guidelines (see Skill Cards #3A and 3B)
Report any broken slide immediately to the teacher
Procedure (Part 1): Identifying Stages of Cell Division
___1.
___2.
___3.
___4.
Skills
In the Data/Analysis (Part 1) section titled “Cells in Various Stages of Cell Division,” label the stage of cell
division (Interphase, Prophase, Metaphase, Anaphase or Telophase), under the picture of each cell. You
should have 13 Interphase, 11 Prophase, 3 Metaphase, 2 Anaphase, and 1 Telophase.
Once all cells are labeled, check with teacher for correctness before proceeding to the next step.
Teacher initials: _______
Neatly hi-lite or shade in the boxes containing the cells accordingly:

Interphase = yellow (13 cells)

Anaphase = blue (2 cells)

Prophase = pink/red (11 cells)

Telophase = green (1 cells)

Metaphase = orange (3 cells)
In Table 1, calculate the percentage of time spent in each stage of the cell cycle.
Applications
Concepts
pg. 2
Name _________________________________
Due Date _______________
Period ________
Data/Analysis (Part 1):
Cells in Various Stages of Cell Division
Table 1: Cells Found in Each Stage
% of cells in each stage =
# of cells
Interphase
Prophase
Metaphase
Anaphase
Telophase
TOTAL
13
11
3
2
1
= 30
% of cells
Skills
= 100%
Applications
Concepts
pg. 3
Name _________________________________
Due Date _______________
Period ________
Calculations (Part 1)
You know how many of the cells are in each phase of mitosis at any given point. How does that relate to time?
Think of it this way: If someone took pictures of you every 2 minutes for 24 hours, what would be the likelihood
of them snapping a picture in which you were sneezing? What would be the likelihood of them snapping a
picture of you in the hall between 3rd and 4th periods? What would be the likelihood of them snapping a picture
of you sleeping? For the average person, there may not be any pictures of them sneezing because it doesn’t
happen very often and it’s really fast; there will be 2 or 3 pictures of them during the passing period between 3rd
and 4th periods; and there will be around 30 pictures for every hour spent sleeping.
So, whatever phase you have the most pictures of is the phase that the most time is spent in! You can calculate how
much time that is if you know the length of the cell cycle for the tissue you’re looking at. If there are 240 pictures of you
sleeping, you slept about 8 hours because 30 pictures are taken every hour. For the onion cells, the cycle is about 12
hours. Use the percent of cells in each phase from Table 1 to complete the calculations below.
Time spent in phase = 12 hours x (% of cells) = ___________hrs
1.
2.
3.
4.
5.
Time
Time
Time
Time
Time
spent
spent
spent
spent
spent
in
in
in
in
in
interphase
prophase
metaphase
anaphase
telophase
= 12 hours x ____________ = __________________hrs
= 12 hours x ____________ = __________________hrs
= 12 hours x ____________ = __________________hrs
= 12 hours x ____________ = __________________hrs
= 12 hours x ____________ = __________________hrs
Procedure (Part 2)
Interpreting a Photomicrograph of an Onion Root Tip
The picture above was taken through the eye piece of a light microscope under 1000X
magnification. The picture is of the portion of the root that is dividing the fastest in an onion, Allium.
When pictures are taken using a magnifying lens such as in a microscope, they are called
photomicrographs.
The photo was printed out on a rectangle, but when you look through a microscope, your field
of view is a circle. A circle has been superimposed on the photo to represent this for you.
Correctly label the drawing in Figure 1 using proper scientific drawing and labeling rules: title
above, magnification below, straight label lines out to the right that do not overlap.
Skills
Applications
Concepts
pg. 4
Name _________________________________
Figure 1:
Due Date _______________
Period ________
________________________________
________
Using a ruler, in your scientific drawing label:

A cell in interphase

A cell in prophase

A cell in metaphase

A cell in anaphase

A cell in telophase
In your own words describe what you see in your field of view by describing what the cells in the
following stages look like to you. Be sure to include the phase names: interphase, prophase,
metaphase, anaphase, and telophase.
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
Skills
Applications
Concepts
pg. 5
Name _________________________________
Due Date _______________
Period ________
Analysis:
1. Looking at Table 1 and your Calculations, during which part of the cell cycle does a cell spend
the most time?
Describe what is happening in this phase to require the cell to spend so much time in this
phase.
2. Looking at Table 1 and your Calculations, during which part of the cell cycle does the cell
spend the least amount of time?
3. Describe is happening to the nuclear envelope & chromosomes in a plant cell during :
a. Interphase-
b. Prophasec. Metaphased. Anaphasee. Telophase-
4. What is the name of the structure that begins to form during telophase in a plant cell that will
ultimately divide the cell into 2 separate cells? ___________________ __________________
What is the name of the structure that forms when an animal cell is dividing that ultimately
splits the cell into 2 separate cells? ______________________ ___________________
5. What can result if mitosis is not regulated properly by the cell (if the cells divide
uncontrollably)? _____________________
Skills
Applications
Concepts
pg. 6